diff --git a/.clang-format b/.clang-format index 8d01225bfcb7..bcf60344f9f5 100644 --- a/.clang-format +++ b/.clang-format @@ -222,6 +222,7 @@ ForEachMacros: - 'for_each_component_dais' - 'for_each_component_dais_safe' - 'for_each_console' + - 'for_each_console_srcu' - 'for_each_cpu' - 'for_each_cpu_and' - 'for_each_cpu_not' diff --git a/arch/m68k/emu/nfcon.c b/arch/m68k/emu/nfcon.c index 557d60867f98..6fdc13610565 100644 --- a/arch/m68k/emu/nfcon.c +++ b/arch/m68k/emu/nfcon.c @@ -49,7 +49,7 @@ static void nfcon_write(struct console *con, const char *str, static struct tty_driver *nfcon_device(struct console *con, int *index) { *index = 0; - return (con->flags & CON_ENABLED) ? nfcon_tty_driver : NULL; + return console_is_registered(con) ? nfcon_tty_driver : NULL; } static struct console nf_console = { @@ -107,6 +107,11 @@ static int __init nf_debug_setup(char *arg) stderr_id = nf_get_id("NF_STDERR"); if (stderr_id) { + /* + * The console will be enabled when debug=nfcon is specified + * as a kernel parameter. Since this is a non-standard way + * of enabling consoles, it must be explicitly enabled. + */ nf_console.flags |= CON_ENABLED; register_console(&nf_console); } @@ -151,7 +156,7 @@ static int __init nfcon_init(void) nfcon_tty_driver = driver; - if (!(nf_console.flags & CON_ENABLED)) + if (!console_is_registered(&nf_console)) register_console(&nf_console); return 0; diff --git a/arch/um/kernel/kmsg_dump.c b/arch/um/kernel/kmsg_dump.c index 0224fcb36e22..427dd5a61a38 100644 --- a/arch/um/kernel/kmsg_dump.c +++ b/arch/um/kernel/kmsg_dump.c @@ -16,20 +16,26 @@ static void kmsg_dumper_stdout(struct kmsg_dumper *dumper, struct console *con; unsigned long flags; size_t len = 0; + int cookie; - /* only dump kmsg when no console is available */ - if (!console_trylock()) - return; + /* + * If no consoles are available to output crash information, dump + * the kmsg buffer to stdout. + */ - for_each_console(con) { - if(strcmp(con->name, "tty") == 0 && - (con->flags & (CON_ENABLED | CON_CONSDEV)) != 0) { + cookie = console_srcu_read_lock(); + for_each_console_srcu(con) { + /* + * The ttynull console and disabled consoles are ignored + * since they cannot output. All other consoles are + * expected to output the crash information. + */ + if (strcmp(con->name, "ttynull") != 0 && + (console_srcu_read_flags(con) & CON_ENABLED)) { break; } } - - console_unlock(); - + console_srcu_read_unlock(cookie); if (con) return; diff --git a/drivers/firmware/efi/earlycon.c b/drivers/firmware/efi/earlycon.c index a52236e11e5f..4d6c5327471a 100644 --- a/drivers/firmware/efi/earlycon.c +++ b/drivers/firmware/efi/earlycon.c @@ -29,8 +29,8 @@ static void *efi_fb; */ static int __init efi_earlycon_remap_fb(void) { - /* bail if there is no bootconsole or it has been disabled already */ - if (!earlycon_console || !(earlycon_console->flags & CON_ENABLED)) + /* bail if there is no bootconsole or it was unregistered already */ + if (!earlycon_console || !console_is_registered(earlycon_console)) return 0; efi_fb = memremap(fb_base, screen_info.lfb_size, @@ -42,8 +42,8 @@ early_initcall(efi_earlycon_remap_fb); static int __init efi_earlycon_unmap_fb(void) { - /* unmap the bootconsole fb unless keep_bootcon has left it enabled */ - if (efi_fb && !(earlycon_console->flags & CON_ENABLED)) + /* unmap the bootconsole fb unless keep_bootcon left it registered */ + if (efi_fb && !console_is_registered(earlycon_console)) memunmap(efi_fb); return 0; } diff --git a/drivers/net/netconsole.c b/drivers/net/netconsole.c index bdff9ac5056d..4f4f79532c6c 100644 --- a/drivers/net/netconsole.c +++ b/drivers/net/netconsole.c @@ -332,10 +332,8 @@ static ssize_t enabled_store(struct config_item *item, } if (enabled) { /* true */ - if (nt->extended && !(netconsole_ext.flags & CON_ENABLED)) { - netconsole_ext.flags |= CON_ENABLED; + if (nt->extended && !console_is_registered(&netconsole_ext)) register_console(&netconsole_ext); - } /* * Skip netpoll_parse_options() -- all the attributes are @@ -869,7 +867,7 @@ static void write_msg(struct console *con, const char *msg, unsigned int len) static struct console netconsole_ext = { .name = "netcon_ext", - .flags = CON_EXTENDED, /* starts disabled, registered on first use */ + .flags = CON_ENABLED | CON_EXTENDED, .write = write_ext_msg, }; @@ -883,6 +881,7 @@ static int __init init_netconsole(void) { int err; struct netconsole_target *nt, *tmp; + bool extended = false; unsigned long flags; char *target_config; char *input = config; @@ -895,11 +894,12 @@ static int __init init_netconsole(void) goto fail; } /* Dump existing printks when we register */ - if (nt->extended) - netconsole_ext.flags |= CON_PRINTBUFFER | - CON_ENABLED; - else + if (nt->extended) { + extended = true; + netconsole_ext.flags |= CON_PRINTBUFFER; + } else { netconsole.flags |= CON_PRINTBUFFER; + } spin_lock_irqsave(&target_list_lock, flags); list_add(&nt->list, &target_list); @@ -915,7 +915,7 @@ static int __init init_netconsole(void) if (err) goto undonotifier; - if (netconsole_ext.flags & CON_ENABLED) + if (extended) register_console(&netconsole_ext); register_console(&netconsole); pr_info("network logging started\n"); @@ -945,7 +945,8 @@ static void __exit cleanup_netconsole(void) { struct netconsole_target *nt, *tmp; - unregister_console(&netconsole_ext); + if (console_is_registered(&netconsole_ext)) + unregister_console(&netconsole_ext); unregister_console(&netconsole); dynamic_netconsole_exit(); unregister_netdevice_notifier(&netconsole_netdev_notifier); diff --git a/drivers/tty/hvc/hvc_console.c b/drivers/tty/hvc/hvc_console.c index 4802cfaa107f..a683e21df19c 100644 --- a/drivers/tty/hvc/hvc_console.c +++ b/drivers/tty/hvc/hvc_console.c @@ -264,8 +264,8 @@ static void hvc_port_destruct(struct tty_port *port) static void hvc_check_console(int index) { - /* Already enabled, bail out */ - if (hvc_console.flags & CON_ENABLED) + /* Already registered, bail out */ + if (console_is_registered(&hvc_console)) return; /* If this index is what the user requested, then register diff --git a/drivers/tty/serial/8250/8250_core.c b/drivers/tty/serial/8250/8250_core.c index 94fbf0add2ce..74568292186f 100644 --- a/drivers/tty/serial/8250/8250_core.c +++ b/drivers/tty/serial/8250/8250_core.c @@ -565,7 +565,7 @@ serial8250_register_ports(struct uart_driver *drv, struct device *dev) up->port.dev = dev; - if (uart_console_enabled(&up->port)) + if (uart_console_registered(&up->port)) pm_runtime_get_sync(up->port.dev); serial8250_apply_quirks(up); diff --git a/drivers/tty/serial/earlycon.c b/drivers/tty/serial/earlycon.c index a5f380584cda..4f6e9bf57169 100644 --- a/drivers/tty/serial/earlycon.c +++ b/drivers/tty/serial/earlycon.c @@ -181,7 +181,7 @@ int __init setup_earlycon(char *buf) if (!buf || !buf[0]) return -EINVAL; - if (early_con.flags & CON_ENABLED) + if (console_is_registered(&early_con)) return -EALREADY; again: @@ -253,7 +253,7 @@ int __init of_setup_earlycon(const struct earlycon_id *match, bool big_endian; u64 addr; - if (early_con.flags & CON_ENABLED) + if (console_is_registered(&early_con)) return -EALREADY; spin_lock_init(&port->lock); diff --git a/drivers/tty/serial/kgdboc.c b/drivers/tty/serial/kgdboc.c index 7aa37be3216a..a3ed9b34e2ab 100644 --- a/drivers/tty/serial/kgdboc.c +++ b/drivers/tty/serial/kgdboc.c @@ -189,9 +189,27 @@ static int configure_kgdboc(void) if (kgdboc_register_kbd(&cptr)) goto do_register; + /* + * tty_find_polling_driver() can call uart_set_options() + * (via poll_init) to configure the uart. Take the console_list_lock + * in order to synchronize against register_console(), which can also + * configure the uart via uart_set_options(). This also allows safe + * traversal of the console list. + */ + console_list_lock(); + p = tty_find_polling_driver(cptr, &tty_line); - if (!p) + if (!p) { + console_list_unlock(); goto noconfig; + } + + /* + * Take console_lock to serialize device() callback with + * other console operations. For example, fg_console is + * modified under console_lock when switching vt. + */ + console_lock(); for_each_console(cons) { int idx; @@ -202,6 +220,10 @@ static int configure_kgdboc(void) } } + console_unlock(); + + console_list_unlock(); + kgdb_tty_driver = p; kgdb_tty_line = tty_line; @@ -449,6 +471,7 @@ static void kgdboc_earlycon_pre_exp_handler(void) { struct console *con; static bool already_warned; + int cookie; if (already_warned) return; @@ -461,9 +484,14 @@ static void kgdboc_earlycon_pre_exp_handler(void) * serial drivers might be OK with this, print a warning once per * boot if we detect this case. */ - for_each_console(con) + cookie = console_srcu_read_lock(); + for_each_console_srcu(con) { if (con == kgdboc_earlycon_io_ops.cons) - return; + break; + } + console_srcu_read_unlock(cookie); + if (con) + return; already_warned = true; pr_warn("kgdboc_earlycon is still using bootconsole\n"); @@ -528,7 +556,15 @@ static int __init kgdboc_earlycon_init(char *opt) * Look for a matching console, or if the name was left blank just * pick the first one we find. */ - console_lock(); + + /* + * Hold the console_list_lock to guarantee that no consoles are + * unregistered until the kgdboc_earlycon setup is complete. + * Trapping the exit() callback relies on exit() not being + * called until the trap is setup. This also allows safe + * traversal of the console list and race-free reading of @flags. + */ + console_list_lock(); for_each_console(con) { if (con->write && con->read && (con->flags & (CON_BOOT | CON_ENABLED)) && @@ -570,7 +606,7 @@ static int __init kgdboc_earlycon_init(char *opt) } unlock: - console_unlock(); + console_list_unlock(); /* Non-zero means malformed option so we always return zero */ return 0; diff --git a/drivers/tty/serial/pic32_uart.c b/drivers/tty/serial/pic32_uart.c index 2beada66c824..c38754d593ca 100644 --- a/drivers/tty/serial/pic32_uart.c +++ b/drivers/tty/serial/pic32_uart.c @@ -843,7 +843,7 @@ console_initcall(pic32_console_init); */ static int __init pic32_late_console_init(void) { - if (!(pic32_console.flags & CON_ENABLED)) + if (!console_is_registered(&pic32_console)) register_console(&pic32_console); return 0; @@ -919,7 +919,7 @@ static int pic32_uart_probe(struct platform_device *pdev) } #ifdef CONFIG_SERIAL_PIC32_CONSOLE - if (uart_console_enabled(port)) { + if (uart_console_registered(port)) { /* The peripheral clock has been enabled by console_setup, * so disable it till the port is used. */ diff --git a/drivers/tty/serial/samsung_tty.c b/drivers/tty/serial/samsung_tty.c index 77d1363029f5..9c252c9ca95a 100644 --- a/drivers/tty/serial/samsung_tty.c +++ b/drivers/tty/serial/samsung_tty.c @@ -1732,7 +1732,7 @@ static void __init s3c24xx_serial_register_console(void) static void s3c24xx_serial_unregister_console(void) { - if (s3c24xx_serial_console.flags & CON_ENABLED) + if (console_is_registered(&s3c24xx_serial_console)) unregister_console(&s3c24xx_serial_console); } diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c index 179ee199df34..b9fbbee598b8 100644 --- a/drivers/tty/serial/serial_core.c +++ b/drivers/tty/serial/serial_core.c @@ -2223,11 +2223,11 @@ uart_set_options(struct uart_port *port, struct console *co, /* * Ensure that the serial-console lock is initialised early. * - * Note that the console-enabled check is needed because of kgdboc, - * which can end up calling uart_set_options() for an already enabled + * Note that the console-registered check is needed because + * kgdboc can call uart_set_options() for an already registered * console via tty_find_polling_driver() and uart_poll_init(). */ - if (!uart_console_enabled(port) && !port->console_reinit) + if (!uart_console_registered_locked(port) && !port->console_reinit) uart_port_spin_lock_init(port); memset(&termios, 0, sizeof(struct ktermios)); @@ -2573,7 +2573,7 @@ uart_configure_port(struct uart_driver *drv, struct uart_state *state, * successfully registered yet, try to re-register it. * It may be that the port was not available. */ - if (port->cons && !(port->cons->flags & CON_ENABLED)) + if (port->cons && !console_is_registered(port->cons)) register_console(port->cons); /* @@ -2956,7 +2956,7 @@ static ssize_t console_show(struct device *dev, mutex_lock(&port->mutex); uport = uart_port_check(state); if (uport) - console = uart_console_enabled(uport); + console = uart_console_registered(uport); mutex_unlock(&port->mutex); return sprintf(buf, "%c\n", console ? 'Y' : 'N'); @@ -2978,7 +2978,7 @@ static ssize_t console_store(struct device *dev, mutex_lock(&port->mutex); uport = uart_port_check(state); if (uport) { - oldconsole = uart_console_enabled(uport); + oldconsole = uart_console_registered(uport); if (oldconsole && !newconsole) { ret = unregister_console(uport->cons); } else if (!oldconsole && newconsole) { @@ -3086,7 +3086,7 @@ int uart_add_one_port(struct uart_driver *drv, struct uart_port *uport) * If this port is in use as a console then the spinlock is already * initialised. */ - if (!uart_console_enabled(uport)) + if (!uart_console_registered(uport)) uart_port_spin_lock_init(uport); if (uport->cons && uport->dev) diff --git a/drivers/tty/serial/sh-sci.c b/drivers/tty/serial/sh-sci.c index 62f773286d44..76452fe2af86 100644 --- a/drivers/tty/serial/sh-sci.c +++ b/drivers/tty/serial/sh-sci.c @@ -3054,15 +3054,29 @@ static struct console serial_console = { }; #ifdef CONFIG_SUPERH +static char early_serial_buf[32]; + +static int early_serial_console_setup(struct console *co, char *options) +{ + /* + * This early console is always registered using the earlyprintk= + * parameter, which does not call add_preferred_console(). Thus + * @options is always NULL and the options for this early console + * are passed using a custom buffer. + */ + WARN_ON(options); + + return serial_console_setup(co, early_serial_buf); +} + static struct console early_serial_console = { .name = "early_ttySC", .write = serial_console_write, + .setup = early_serial_console_setup, .flags = CON_PRINTBUFFER, .index = -1, }; -static char early_serial_buf[32]; - static int sci_probe_earlyprintk(struct platform_device *pdev) { const struct plat_sci_port *cfg = dev_get_platdata(&pdev->dev); @@ -3074,8 +3088,6 @@ static int sci_probe_earlyprintk(struct platform_device *pdev) sci_init_single(pdev, &sci_ports[pdev->id], pdev->id, cfg, true); - serial_console_setup(&early_serial_console, early_serial_buf); - if (!strstr(early_serial_buf, "keep")) early_serial_console.flags |= CON_BOOT; diff --git a/drivers/tty/serial/xilinx_uartps.c b/drivers/tty/serial/xilinx_uartps.c index 2eff7cff57c4..0cbd1892c53b 100644 --- a/drivers/tty/serial/xilinx_uartps.c +++ b/drivers/tty/serial/xilinx_uartps.c @@ -1631,7 +1631,7 @@ static int cdns_uart_probe(struct platform_device *pdev) #ifdef CONFIG_SERIAL_XILINX_PS_UART_CONSOLE /* This is not port which is used for console that's why clean it up */ if (console_port == port && - !(cdns_uart_uart_driver.cons->flags & CON_ENABLED)) { + !console_is_registered(cdns_uart_uart_driver.cons)) { console_port = NULL; cdns_uart_console.index = -1; } diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c index de06c3c2ff70..cafdff575716 100644 --- a/drivers/tty/tty_io.c +++ b/drivers/tty/tty_io.c @@ -3526,7 +3526,14 @@ static ssize_t show_cons_active(struct device *dev, struct console *c; ssize_t count = 0; - console_lock(); + /* + * Hold the console_list_lock to guarantee that no consoles are + * unregistered until all console processing is complete. + * This also allows safe traversal of the console list and + * race-free reading of @flags. + */ + console_list_lock(); + for_each_console(c) { if (!c->device) continue; @@ -3538,6 +3545,13 @@ static ssize_t show_cons_active(struct device *dev, if (i >= ARRAY_SIZE(cs)) break; } + + /* + * Take console_lock to serialize device() callback with + * other console operations. For example, fg_console is + * modified under console_lock when switching vt. + */ + console_lock(); while (i--) { int index = cs[i]->index; struct tty_driver *drv = cs[i]->device(cs[i], &index); @@ -3553,6 +3567,8 @@ static ssize_t show_cons_active(struct device *dev, } console_unlock(); + console_list_unlock(); + return count; } static DEVICE_ATTR(active, S_IRUGO, show_cons_active, NULL); diff --git a/drivers/usb/early/xhci-dbc.c b/drivers/usb/early/xhci-dbc.c index bfb7e2b85299..797047154820 100644 --- a/drivers/usb/early/xhci-dbc.c +++ b/drivers/usb/early/xhci-dbc.c @@ -927,7 +927,7 @@ void __init early_xdbc_register_console(void) static void xdbc_unregister_console(void) { - if (early_xdbc_console.flags & CON_ENABLED) + if (console_is_registered(&early_xdbc_console)) unregister_console(&early_xdbc_console); } diff --git a/drivers/video/fbdev/xen-fbfront.c b/drivers/video/fbdev/xen-fbfront.c index 4d2694d904aa..8752d389e382 100644 --- a/drivers/video/fbdev/xen-fbfront.c +++ b/drivers/video/fbdev/xen-fbfront.c @@ -504,18 +504,14 @@ static void xenfb_make_preferred_console(void) if (console_set_on_cmdline) return; - console_lock(); + console_list_lock(); for_each_console(c) { if (!strcmp(c->name, "tty") && c->index == 0) break; } - console_unlock(); - if (c) { - unregister_console(c); - c->flags |= CON_CONSDEV; - c->flags &= ~CON_PRINTBUFFER; /* don't print again */ - register_console(c); - } + if (c) + console_force_preferred_locked(c); + console_list_unlock(); } static int xenfb_resume(struct xenbus_device *dev) diff --git a/fs/proc/consoles.c b/fs/proc/consoles.c index dfe6ce3505ce..e0758fe7936d 100644 --- a/fs/proc/consoles.c +++ b/fs/proc/consoles.c @@ -33,7 +33,16 @@ static int show_console_dev(struct seq_file *m, void *v) if (con->device) { const struct tty_driver *driver; int index; + + /* + * Take console_lock to serialize device() callback with + * other console operations. For example, fg_console is + * modified under console_lock when switching vt. + */ + console_lock(); driver = con->device(con, &index); + console_unlock(); + if (driver) { dev = MKDEV(driver->major, driver->minor_start); dev += index; @@ -63,7 +72,12 @@ static void *c_start(struct seq_file *m, loff_t *pos) struct console *con; loff_t off = 0; - console_lock(); + /* + * Hold the console_list_lock to guarantee safe traversal of the + * console list. SRCU cannot be used because there is no + * place to store the SRCU cookie. + */ + console_list_lock(); for_each_console(con) if (off++ == *pos) break; @@ -74,13 +88,14 @@ static void *c_start(struct seq_file *m, loff_t *pos) static void *c_next(struct seq_file *m, void *v, loff_t *pos) { struct console *con = v; + ++*pos; - return con->next; + return hlist_entry_safe(con->node.next, struct console, node); } static void c_stop(struct seq_file *m, void *v) { - console_unlock(); + console_list_unlock(); } static const struct seq_operations consoles_op = { diff --git a/include/linux/console.h b/include/linux/console.h index 8c1686e2c233..9cea254b34b8 100644 --- a/include/linux/console.h +++ b/include/linux/console.h @@ -15,6 +15,7 @@ #define _LINUX_CONSOLE_H_ 1 #include +#include #include struct vc_data; @@ -154,14 +155,132 @@ struct console { u64 seq; unsigned long dropped; void *data; - struct console *next; + struct hlist_node node; }; -/* - * for_each_console() allows you to iterate on each console +#ifdef CONFIG_LOCKDEP +extern void lockdep_assert_console_list_lock_held(void); +#else +static inline void lockdep_assert_console_list_lock_held(void) +{ +} +#endif + +#ifdef CONFIG_DEBUG_LOCK_ALLOC +extern bool console_srcu_read_lock_is_held(void); +#else +static inline bool console_srcu_read_lock_is_held(void) +{ + return 1; +} +#endif + +extern int console_srcu_read_lock(void); +extern void console_srcu_read_unlock(int cookie); + +extern void console_list_lock(void) __acquires(console_mutex); +extern void console_list_unlock(void) __releases(console_mutex); + +extern struct hlist_head console_list; + +/** + * console_srcu_read_flags - Locklessly read the console flags + * @con: struct console pointer of console to read flags from + * + * This function provides the necessary READ_ONCE() and data_race() + * notation for locklessly reading the console flags. The READ_ONCE() + * in this function matches the WRITE_ONCE() when @flags are modified + * for registered consoles with console_srcu_write_flags(). + * + * Only use this function to read console flags when locklessly + * iterating the console list via srcu. + * + * Context: Any context. */ -#define for_each_console(con) \ - for (con = console_drivers; con != NULL; con = con->next) +static inline short console_srcu_read_flags(const struct console *con) +{ + WARN_ON_ONCE(!console_srcu_read_lock_is_held()); + + /* + * Locklessly reading console->flags provides a consistent + * read value because there is at most one CPU modifying + * console->flags and that CPU is using only read-modify-write + * operations to do so. + */ + return data_race(READ_ONCE(con->flags)); +} + +/** + * console_srcu_write_flags - Write flags for a registered console + * @con: struct console pointer of console to write flags to + * @flags: new flags value to write + * + * Only use this function to write flags for registered consoles. It + * requires holding the console_list_lock. + * + * Context: Any context. + */ +static inline void console_srcu_write_flags(struct console *con, short flags) +{ + lockdep_assert_console_list_lock_held(); + + /* This matches the READ_ONCE() in console_srcu_read_flags(). */ + WRITE_ONCE(con->flags, flags); +} + +/* Variant of console_is_registered() when the console_list_lock is held. */ +static inline bool console_is_registered_locked(const struct console *con) +{ + lockdep_assert_console_list_lock_held(); + return !hlist_unhashed(&con->node); +} + +/* + * console_is_registered - Check if the console is registered + * @con: struct console pointer of console to check + * + * Context: Process context. May sleep while acquiring console list lock. + * Return: true if the console is in the console list, otherwise false. + * + * If false is returned for a console that was previously registered, it + * can be assumed that the console's unregistration is fully completed, + * including the exit() callback after console list removal. + */ +static inline bool console_is_registered(const struct console *con) +{ + bool ret; + + console_list_lock(); + ret = console_is_registered_locked(con); + console_list_unlock(); + return ret; +} + +/** + * for_each_console_srcu() - Iterator over registered consoles + * @con: struct console pointer used as loop cursor + * + * Although SRCU guarantees the console list will be consistent, the + * struct console fields may be updated by other CPUs while iterating. + * + * Requires console_srcu_read_lock to be held. Can be invoked from + * any context. + */ +#define for_each_console_srcu(con) \ + hlist_for_each_entry_srcu(con, &console_list, node, \ + console_srcu_read_lock_is_held()) + +/** + * for_each_console() - Iterator over registered consoles + * @con: struct console pointer used as loop cursor + * + * The console list and the console->flags are immutable while iterating. + * + * Requires console_list_lock to be held. + */ +#define for_each_console(con) \ + lockdep_assert_console_list_lock_held(); \ + hlist_for_each_entry(con, &console_list, node) extern int console_set_on_cmdline; extern struct console *early_console; @@ -172,9 +291,9 @@ enum con_flush_mode { }; extern int add_preferred_console(char *name, int idx, char *options); +extern void console_force_preferred_locked(struct console *con); extern void register_console(struct console *); extern int unregister_console(struct console *); -extern struct console *console_drivers; extern void console_lock(void); extern int console_trylock(void); extern void console_unlock(void); diff --git a/include/linux/rcutiny.h b/include/linux/rcutiny.h index 5c271bf3a1e7..68f9070aa111 100644 --- a/include/linux/rcutiny.h +++ b/include/linux/rcutiny.h @@ -152,11 +152,7 @@ static inline bool rcu_preempt_need_deferred_qs(struct task_struct *t) return false; } static inline void rcu_preempt_deferred_qs(struct task_struct *t) { } -#ifdef CONFIG_SRCU void rcu_scheduler_starting(void); -#else /* #ifndef CONFIG_SRCU */ -static inline void rcu_scheduler_starting(void) { } -#endif /* #else #ifndef CONFIG_SRCU */ static inline void rcu_end_inkernel_boot(void) { } static inline bool rcu_inkernel_boot_has_ended(void) { return true; } static inline bool rcu_is_watching(void) { return true; } diff --git a/include/linux/serial_core.h b/include/linux/serial_core.h index d657f2a42a7b..91871464b99d 100644 --- a/include/linux/serial_core.h +++ b/include/linux/serial_core.h @@ -743,9 +743,15 @@ static const bool earlycon_acpi_spcr_enable EARLYCON_USED_OR_UNUSED; static inline int setup_earlycon(char *buf) { return 0; } #endif -static inline bool uart_console_enabled(struct uart_port *port) +/* Variant of uart_console_registered() when the console_list_lock is held. */ +static inline bool uart_console_registered_locked(struct uart_port *port) { - return uart_console(port) && (port->cons->flags & CON_ENABLED); + return uart_console(port) && console_is_registered_locked(port->cons); +} + +static inline bool uart_console_registered(struct uart_port *port) +{ + return uart_console(port) && console_is_registered(port->cons); } struct uart_port *uart_get_console(struct uart_port *ports, int nr, diff --git a/include/linux/srcu.h b/include/linux/srcu.h index f0814ffca34b..9b9d0bbf1d3c 100644 --- a/include/linux/srcu.h +++ b/include/linux/srcu.h @@ -47,11 +47,8 @@ int init_srcu_struct(struct srcu_struct *ssp); #include #elif defined(CONFIG_TREE_SRCU) #include -#elif defined(CONFIG_SRCU) -#error "Unknown SRCU implementation specified to kernel configuration" #else -/* Dummy definition for things like notifiers. Actual use gets link error. */ -struct srcu_struct { }; +#error "Unknown SRCU implementation specified to kernel configuration" #endif void call_srcu(struct srcu_struct *ssp, struct rcu_head *head, @@ -78,11 +75,7 @@ static inline void __srcu_read_unlock_nmisafe(struct srcu_struct *ssp, int idx) } #endif /* CONFIG_NEED_SRCU_NMI_SAFE */ -#ifdef CONFIG_SRCU void srcu_init(void); -#else /* #ifdef CONFIG_SRCU */ -static inline void srcu_init(void) { } -#endif /* #else #ifdef CONFIG_SRCU */ #ifdef CONFIG_DEBUG_LOCK_ALLOC diff --git a/kernel/debug/kdb/kdb_io.c b/kernel/debug/kdb/kdb_io.c index 67d3c48a1522..5c7e9ba7cd6b 100644 --- a/kernel/debug/kdb/kdb_io.c +++ b/kernel/debug/kdb/kdb_io.c @@ -545,6 +545,7 @@ static void kdb_msg_write(const char *msg, int msg_len) { struct console *c; const char *cp; + int cookie; int len; if (msg_len == 0) @@ -558,8 +559,20 @@ static void kdb_msg_write(const char *msg, int msg_len) cp++; } - for_each_console(c) { - if (!(c->flags & CON_ENABLED)) + /* + * The console_srcu_read_lock() only provides safe console list + * traversal. The use of the ->write() callback relies on all other + * CPUs being stopped at the moment and console drivers being able to + * handle reentrance when @oops_in_progress is set. + * + * There is no guarantee that every console driver can handle + * reentrance in this way; the developer deploying the debugger + * is responsible for ensuring that the console drivers they + * have selected handle reentrance appropriately. + */ + cookie = console_srcu_read_lock(); + for_each_console_srcu(c) { + if (!(console_srcu_read_flags(c) & CON_ENABLED)) continue; if (c == dbg_io_ops->cons) continue; @@ -577,6 +590,7 @@ static void kdb_msg_write(const char *msg, int msg_len) --oops_in_progress; touch_nmi_watchdog(); } + console_srcu_read_unlock(cookie); } int vkdb_printf(enum kdb_msgsrc src, const char *fmt, va_list ap) diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c index e4f1e7478b52..7decf1e9c486 100644 --- a/kernel/printk/printk.c +++ b/kernel/printk/printk.c @@ -79,13 +79,20 @@ int oops_in_progress; EXPORT_SYMBOL(oops_in_progress); /* - * console_sem protects the console_drivers list, and also - * provides serialisation for access to the entire console - * driver system. + * console_mutex protects console_list updates and console->flags updates. + * The flags are synchronized only for consoles that are registered, i.e. + * accessible via the console list. + */ +static DEFINE_MUTEX(console_mutex); + +/* + * console_sem protects updates to console->seq and console_suspended, + * and also provides serialization for console printing. */ static DEFINE_SEMAPHORE(console_sem); -struct console *console_drivers; -EXPORT_SYMBOL_GPL(console_drivers); +HLIST_HEAD(console_list); +EXPORT_SYMBOL_GPL(console_list); +DEFINE_STATIC_SRCU(console_srcu); /* * System may need to suppress printk message under certain @@ -103,6 +110,19 @@ static int __read_mostly suppress_panic_printk; static struct lockdep_map console_lock_dep_map = { .name = "console_lock" }; + +void lockdep_assert_console_list_lock_held(void) +{ + lockdep_assert_held(&console_mutex); +} +EXPORT_SYMBOL(lockdep_assert_console_list_lock_held); +#endif + +#ifdef CONFIG_DEBUG_LOCK_ALLOC +bool console_srcu_read_lock_is_held(void) +{ + return srcu_read_lock_held(&console_srcu); +} #endif enum devkmsg_log_bits { @@ -220,6 +240,69 @@ int devkmsg_sysctl_set_loglvl(struct ctl_table *table, int write, } #endif /* CONFIG_PRINTK && CONFIG_SYSCTL */ +/** + * console_list_lock - Lock the console list + * + * For console list or console->flags updates + */ +void console_list_lock(void) +{ + /* + * In unregister_console() and console_force_preferred_locked(), + * synchronize_srcu() is called with the console_list_lock held. + * Therefore it is not allowed that the console_list_lock is taken + * with the srcu_lock held. + * + * Detecting if this context is really in the read-side critical + * section is only possible if the appropriate debug options are + * enabled. + */ + WARN_ON_ONCE(debug_lockdep_rcu_enabled() && + srcu_read_lock_held(&console_srcu)); + + mutex_lock(&console_mutex); +} +EXPORT_SYMBOL(console_list_lock); + +/** + * console_list_unlock - Unlock the console list + * + * Counterpart to console_list_lock() + */ +void console_list_unlock(void) +{ + mutex_unlock(&console_mutex); +} +EXPORT_SYMBOL(console_list_unlock); + +/** + * console_srcu_read_lock - Register a new reader for the + * SRCU-protected console list + * + * Use for_each_console_srcu() to iterate the console list + * + * Context: Any context. + * Return: A cookie to pass to console_srcu_read_unlock(). + */ +int console_srcu_read_lock(void) +{ + return srcu_read_lock_nmisafe(&console_srcu); +} +EXPORT_SYMBOL(console_srcu_read_lock); + +/** + * console_srcu_read_unlock - Unregister an old reader from + * the SRCU-protected console list + * @cookie: cookie returned from console_srcu_read_lock() + * + * Counterpart to console_srcu_read_lock() + */ +void console_srcu_read_unlock(int cookie) +{ + srcu_read_unlock_nmisafe(&console_srcu, cookie); +} +EXPORT_SYMBOL(console_srcu_read_unlock); + /* * Helper macros to handle lockdep when locking/unlocking console_sem. We use * macros instead of functions so that _RET_IP_ contains useful information. @@ -1814,13 +1897,13 @@ static void console_lock_spinning_enable(void) * safe to start busy waiting for the lock. Second, it checks if * there is a busy waiter and passes the lock rights to her. * - * Important: Callers lose the lock if there was a busy waiter. - * They must not touch items synchronized by console_lock - * in this case. + * Important: Callers lose both the console_lock and the SRCU read lock if + * there was a busy waiter. They must not touch items synchronized by + * console_lock or SRCU read lock in this case. * * Return: 1 if the lock rights were passed, 0 otherwise. */ -static int console_lock_spinning_disable_and_check(void) +static int console_lock_spinning_disable_and_check(int cookie) { int waiter; @@ -1839,6 +1922,12 @@ static int console_lock_spinning_disable_and_check(void) spin_release(&console_owner_dep_map, _THIS_IP_); + /* + * Preserve lockdep lock ordering. Release the SRCU read lock before + * releasing the console_lock. + */ + console_srcu_read_unlock(cookie); + /* * Hand off console_lock to waiter. The waiter will perform * the up(). After this, the waiter is the console_lock owner. @@ -2322,7 +2411,7 @@ static ssize_t msg_print_ext_body(char *buf, size_t size, char *text, size_t text_len, struct dev_printk_info *dev_info) { return 0; } static void console_lock_spinning_enable(void) { } -static int console_lock_spinning_disable_and_check(void) { return 0; } +static int console_lock_spinning_disable_and_check(int cookie) { return 0; } static void call_console_driver(struct console *con, const char *text, size_t len, char *dropped_text) { @@ -2391,7 +2480,7 @@ static int __add_preferred_console(char *name, int idx, char *options, return -E2BIG; if (!brl_options) preferred_console = i; - strlcpy(c->name, name, sizeof(c->name)); + strscpy(c->name, name, sizeof(c->name)); c->options = options; set_user_specified(c, user_specified); braille_set_options(c, brl_options); @@ -2553,10 +2642,10 @@ static int console_cpu_notify(unsigned int cpu) } /** - * console_lock - lock the console system for exclusive use. + * console_lock - block the console subsystem from printing * - * Acquires a lock which guarantees that the caller has - * exclusive access to the console system and the console_drivers list. + * Acquires a lock which guarantees that no consoles will + * be in or enter their write() callback. * * Can sleep, returns nothing. */ @@ -2573,10 +2662,10 @@ void console_lock(void) EXPORT_SYMBOL(console_lock); /** - * console_trylock - try to lock the console system for exclusive use. + * console_trylock - try to block the console subsystem from printing * - * Try to acquire a lock which guarantees that the caller has exclusive - * access to the console system and the console_drivers list. + * Try to acquire a lock which guarantees that no consoles will + * be in or enter their write() callback. * * returns 1 on success, and 0 on failure to acquire the lock. */ @@ -2623,11 +2712,13 @@ static bool abandon_console_lock_in_panic(void) * Check if the given console is currently capable and allowed to print * records. * - * Requires the console_lock. + * Requires the console_srcu_read_lock. */ static inline bool console_is_usable(struct console *con) { - if (!(con->flags & CON_ENABLED)) + short flags = console_srcu_read_flags(con); + + if (!(flags & CON_ENABLED)) return false; if (!con->write) @@ -2638,8 +2729,7 @@ static inline bool console_is_usable(struct console *con) * allocated. So unless they're explicitly marked as being able to * cope (CON_ANYTIME) don't call them until this CPU is officially up. */ - if (!cpu_online(raw_smp_processor_id()) && - !(con->flags & CON_ANYTIME)) + if (!cpu_online(raw_smp_processor_id()) && !(flags & CON_ANYTIME)) return false; return true; @@ -2664,16 +2754,18 @@ static void __console_unlock(void) * DROPPED_TEXT_MAX. Otherwise @dropped_text must be NULL. * * @handover will be set to true if a printk waiter has taken over the - * console_lock, in which case the caller is no longer holding the - * console_lock. Otherwise it is set to false. + * console_lock, in which case the caller is no longer holding both the + * console_lock and the SRCU read lock. Otherwise it is set to false. + * + * @cookie is the cookie from the SRCU read lock. * * Returns false if the given console has no next record to print, otherwise * true. * - * Requires the console_lock. + * Requires the console_lock and the SRCU read lock. */ static bool console_emit_next_record(struct console *con, char *text, char *ext_text, - char *dropped_text, bool *handover) + char *dropped_text, bool *handover, int cookie) { static int panic_console_dropped; struct printk_info info; @@ -2733,7 +2825,7 @@ static bool console_emit_next_record(struct console *con, char *text, char *ext_ con->seq++; - *handover = console_lock_spinning_disable_and_check(); + *handover = console_lock_spinning_disable_and_check(cookie); printk_safe_exit_irqrestore(flags); skip: return true; @@ -2770,6 +2862,7 @@ static bool console_flush_all(bool do_cond_resched, u64 *next_seq, bool *handove bool any_usable = false; struct console *con; bool any_progress; + int cookie; *next_seq = 0; *handover = false; @@ -2777,23 +2870,29 @@ static bool console_flush_all(bool do_cond_resched, u64 *next_seq, bool *handove do { any_progress = false; - for_each_console(con) { + cookie = console_srcu_read_lock(); + for_each_console_srcu(con) { bool progress; if (!console_is_usable(con)) continue; any_usable = true; - if (con->flags & CON_EXTENDED) { + if (console_srcu_read_flags(con) & CON_EXTENDED) { /* Extended consoles do not print "dropped messages". */ progress = console_emit_next_record(con, &text[0], &ext_text[0], NULL, - handover); + handover, cookie); } else { progress = console_emit_next_record(con, &text[0], NULL, &dropped_text[0], - handover); + handover, cookie); } + + /* + * If a handover has occurred, the SRCU read lock + * is already released. + */ if (*handover) return false; @@ -2807,21 +2906,26 @@ static bool console_flush_all(bool do_cond_resched, u64 *next_seq, bool *handove /* Allow panic_cpu to take over the consoles safely. */ if (abandon_console_lock_in_panic()) - return false; + goto abandon; if (do_cond_resched) cond_resched(); } + console_srcu_read_unlock(cookie); } while (any_progress); return any_usable; + +abandon: + console_srcu_read_unlock(cookie); + return false; } /** - * console_unlock - unlock the console system + * console_unlock - unblock the console subsystem from printing * - * Releases the console_lock which the caller holds on the console system - * and the console driver list. + * Releases the console_lock which the caller holds to block printing of + * the console subsystem. * * While the console_lock was held, console output may have been buffered * by printk(). If this is the case, console_unlock(); emits @@ -2899,10 +3003,14 @@ EXPORT_SYMBOL(console_conditional_schedule); void console_unblank(void) { struct console *c; + int cookie; /* - * console_unblank can no longer be called in interrupt context unless - * oops_in_progress is set to 1.. + * Stop console printing because the unblank() callback may + * assume the console is not within its write() callback. + * + * If @oops_in_progress is set, this may be an atomic context. + * In that case, attempt a trylock as best-effort. */ if (oops_in_progress) { if (down_trylock_console_sem() != 0) @@ -2912,9 +3020,14 @@ void console_unblank(void) console_locked = 1; console_may_schedule = 0; - for_each_console(c) - if ((c->flags & CON_ENABLED) && c->unblank) + + cookie = console_srcu_read_lock(); + for_each_console_srcu(c) { + if ((console_srcu_read_flags(c) & CON_ENABLED) && c->unblank) c->unblank(); + } + console_srcu_read_unlock(cookie); + console_unlock(); if (!oops_in_progress) @@ -2941,11 +3054,21 @@ void console_flush_on_panic(enum con_flush_mode mode) if (mode == CONSOLE_REPLAY_ALL) { struct console *c; + int cookie; u64 seq; seq = prb_first_valid_seq(prb); - for_each_console(c) + + cookie = console_srcu_read_lock(); + for_each_console_srcu(c) { + /* + * If the above console_trylock() failed, this is an + * unsynchronized assignment. But in that case, the + * kernel is in "hope and pray" mode anyway. + */ c->seq = seq; + } + console_srcu_read_unlock(cookie); } console_unlock(); } @@ -2957,15 +3080,25 @@ struct tty_driver *console_device(int *index) { struct console *c; struct tty_driver *driver = NULL; + int cookie; + /* + * Take console_lock to serialize device() callback with + * other console operations. For example, fg_console is + * modified under console_lock when switching vt. + */ console_lock(); - for_each_console(c) { + + cookie = console_srcu_read_lock(); + for_each_console_srcu(c) { if (!c->device) continue; driver = c->device(c, index); if (driver) break; } + console_srcu_read_unlock(cookie); + console_unlock(); return driver; } @@ -2978,17 +3111,25 @@ struct tty_driver *console_device(int *index) void console_stop(struct console *console) { __pr_flush(console, 1000, true); - console_lock(); - console->flags &= ~CON_ENABLED; - console_unlock(); + console_list_lock(); + console_srcu_write_flags(console, console->flags & ~CON_ENABLED); + console_list_unlock(); + + /* + * Ensure that all SRCU list walks have completed. All contexts must + * be able to see that this console is disabled so that (for example) + * the caller can suspend the port without risk of another context + * using the port. + */ + synchronize_srcu(&console_srcu); } EXPORT_SYMBOL(console_stop); void console_start(struct console *console) { - console_lock(); - console->flags |= CON_ENABLED; - console_unlock(); + console_list_lock(); + console_srcu_write_flags(console, console->flags | CON_ENABLED); + console_list_unlock(); __pr_flush(console, 1000, true); } EXPORT_SYMBOL(console_start); @@ -3081,6 +3222,72 @@ static void try_enable_default_console(struct console *newcon) (con->flags & CON_BOOT) ? "boot" : "", \ con->name, con->index, ##__VA_ARGS__) +static void console_init_seq(struct console *newcon, bool bootcon_registered) +{ + struct console *con; + bool handover; + + if (newcon->flags & (CON_PRINTBUFFER | CON_BOOT)) { + /* Get a consistent copy of @syslog_seq. */ + mutex_lock(&syslog_lock); + newcon->seq = syslog_seq; + mutex_unlock(&syslog_lock); + } else { + /* Begin with next message added to ringbuffer. */ + newcon->seq = prb_next_seq(prb); + + /* + * If any enabled boot consoles are due to be unregistered + * shortly, some may not be caught up and may be the same + * device as @newcon. Since it is not known which boot console + * is the same device, flush all consoles and, if necessary, + * start with the message of the enabled boot console that is + * the furthest behind. + */ + if (bootcon_registered && !keep_bootcon) { + /* + * Hold the console_lock to stop console printing and + * guarantee safe access to console->seq. + */ + console_lock(); + + /* + * Flush all consoles and set the console to start at + * the next unprinted sequence number. + */ + if (!console_flush_all(true, &newcon->seq, &handover)) { + /* + * Flushing failed. Just choose the lowest + * sequence of the enabled boot consoles. + */ + + /* + * If there was a handover, this context no + * longer holds the console_lock. + */ + if (handover) + console_lock(); + + newcon->seq = prb_next_seq(prb); + for_each_console(con) { + if ((con->flags & CON_BOOT) && + (con->flags & CON_ENABLED) && + con->seq < newcon->seq) { + newcon->seq = con->seq; + } + } + } + + console_unlock(); + } + } +} + +#define console_first() \ + hlist_entry(console_list.first, struct console, node) + +static int unregister_console_locked(struct console *console); + /* * The console driver calls this routine during kernel initialization * to register the console printing procedure with printk() and to @@ -3103,28 +3310,29 @@ static void try_enable_default_console(struct console *newcon) void register_console(struct console *newcon) { struct console *con; - bool bootcon_enabled = false; - bool realcon_enabled = false; + bool bootcon_registered = false; + bool realcon_registered = false; int err; + console_list_lock(); + for_each_console(con) { if (WARN(con == newcon, "console '%s%d' already registered\n", - con->name, con->index)) - return; - } + con->name, con->index)) { + goto unlock; + } - for_each_console(con) { if (con->flags & CON_BOOT) - bootcon_enabled = true; + bootcon_registered = true; else - realcon_enabled = true; + realcon_registered = true; } /* Do not register boot consoles when there already is a real one. */ - if (newcon->flags & CON_BOOT && realcon_enabled) { + if ((newcon->flags & CON_BOOT) && realcon_registered) { pr_info("Too late to register bootconsole %s%d\n", newcon->name, newcon->index); - return; + goto unlock; } /* @@ -3140,8 +3348,8 @@ void register_console(struct console *newcon) * flag set and will be first in the list. */ if (preferred_console < 0) { - if (!console_drivers || !console_drivers->device || - console_drivers->flags & CON_BOOT) { + if (hlist_empty(&console_list) || !console_first()->device || + console_first()->flags & CON_BOOT) { try_enable_default_console(newcon); } } @@ -3155,7 +3363,7 @@ void register_console(struct console *newcon) /* printk() messages are not printed to the Braille console. */ if (err || newcon->flags & CON_BRL) - return; + goto unlock; /* * If we have a bootconsole, and are switching to a real console, @@ -3163,39 +3371,38 @@ void register_console(struct console *newcon) * the real console are the same physical device, it's annoying to * see the beginning boot messages twice */ - if (bootcon_enabled && + if (bootcon_registered && ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV)) { newcon->flags &= ~CON_PRINTBUFFER; } + newcon->dropped = 0; + console_init_seq(newcon, bootcon_registered); + /* - * Put this console in the list - keep the - * preferred driver at the head of the list. + * Put this console in the list - keep the + * preferred driver at the head of the list. */ - console_lock(); - if ((newcon->flags & CON_CONSDEV) || console_drivers == NULL) { - newcon->next = console_drivers; - console_drivers = newcon; - if (newcon->next) - newcon->next->flags &= ~CON_CONSDEV; - /* Ensure this flag is always set for the head of the list */ + if (hlist_empty(&console_list)) { + /* Ensure CON_CONSDEV is always set for the head. */ newcon->flags |= CON_CONSDEV; + hlist_add_head_rcu(&newcon->node, &console_list); + + } else if (newcon->flags & CON_CONSDEV) { + /* Only the new head can have CON_CONSDEV set. */ + console_srcu_write_flags(console_first(), console_first()->flags & ~CON_CONSDEV); + hlist_add_head_rcu(&newcon->node, &console_list); + } else { - newcon->next = console_drivers->next; - console_drivers->next = newcon; + hlist_add_behind_rcu(&newcon->node, console_list.first); } - newcon->dropped = 0; - if (newcon->flags & CON_PRINTBUFFER) { - /* Get a consistent copy of @syslog_seq. */ - mutex_lock(&syslog_lock); - newcon->seq = syslog_seq; - mutex_unlock(&syslog_lock); - } else { - /* Begin with next message. */ - newcon->seq = prb_next_seq(prb); - } - console_unlock(); + /* + * No need to synchronize SRCU here! The caller does not rely + * on all contexts being able to see the new console before + * register_console() completes. + */ + console_sysfs_notify(); /* @@ -3206,21 +3413,28 @@ void register_console(struct console *newcon) * went to the bootconsole (that they do not see on the real console) */ con_printk(KERN_INFO, newcon, "enabled\n"); - if (bootcon_enabled && + if (bootcon_registered && ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV) && !keep_bootcon) { - for_each_console(con) + struct hlist_node *tmp; + + hlist_for_each_entry_safe(con, tmp, &console_list, node) { if (con->flags & CON_BOOT) - unregister_console(con); + unregister_console_locked(con); + } } +unlock: + console_list_unlock(); } EXPORT_SYMBOL(register_console); -int unregister_console(struct console *console) +/* Must be called under console_list_lock(). */ +static int unregister_console_locked(struct console *console) { - struct console *con; int res; + lockdep_assert_console_list_lock_held(); + con_printk(KERN_INFO, console, "disabled\n"); res = _braille_unregister_console(console); @@ -3229,48 +3443,94 @@ int unregister_console(struct console *console) if (res > 0) return 0; - res = -ENODEV; - console_lock(); - if (console_drivers == console) { - console_drivers=console->next; - res = 0; - } else { - for_each_console(con) { - if (con->next == console) { - con->next = console->next; - res = 0; - break; - } - } - } + /* Disable it unconditionally */ + console_srcu_write_flags(console, console->flags & ~CON_ENABLED); - if (res) - goto out_disable_unlock; + if (!console_is_registered_locked(console)) + return -ENODEV; + + hlist_del_init_rcu(&console->node); /* + * * If this isn't the last console and it has CON_CONSDEV set, we * need to set it on the next preferred console. + * + * + * The above makes no sense as there is no guarantee that the next + * console has any device attached. Oh well.... */ - if (console_drivers != NULL && console->flags & CON_CONSDEV) - console_drivers->flags |= CON_CONSDEV; + if (!hlist_empty(&console_list) && console->flags & CON_CONSDEV) + console_srcu_write_flags(console_first(), console_first()->flags | CON_CONSDEV); + + /* + * Ensure that all SRCU list walks have completed. All contexts + * must not be able to see this console in the list so that any + * exit/cleanup routines can be performed safely. + */ + synchronize_srcu(&console_srcu); - console->flags &= ~CON_ENABLED; - console_unlock(); console_sysfs_notify(); if (console->exit) res = console->exit(console); return res; +} -out_disable_unlock: - console->flags &= ~CON_ENABLED; - console_unlock(); +int unregister_console(struct console *console) +{ + int res; + console_list_lock(); + res = unregister_console_locked(console); + console_list_unlock(); return res; } EXPORT_SYMBOL(unregister_console); +/** + * console_force_preferred_locked - force a registered console preferred + * @con: The registered console to force preferred. + * + * Must be called under console_list_lock(). + */ +void console_force_preferred_locked(struct console *con) +{ + struct console *cur_pref_con; + + if (!console_is_registered_locked(con)) + return; + + cur_pref_con = console_first(); + + /* Already preferred? */ + if (cur_pref_con == con) + return; + + /* + * Delete, but do not re-initialize the entry. This allows the console + * to continue to appear registered (via any hlist_unhashed_lockless() + * checks), even though it was briefly removed from the console list. + */ + hlist_del_rcu(&con->node); + + /* + * Ensure that all SRCU list walks have completed so that the console + * can be added to the beginning of the console list and its forward + * list pointer can be re-initialized. + */ + synchronize_srcu(&console_srcu); + + con->flags |= CON_CONSDEV; + WARN_ON(!con->device); + + /* Only the new head can have CON_CONSDEV set. */ + console_srcu_write_flags(cur_pref_con, cur_pref_con->flags & ~CON_CONSDEV); + hlist_add_head_rcu(&con->node, &console_list); +} +EXPORT_SYMBOL(console_force_preferred_locked); + /* * Initialize the console device. This is called *early*, so * we can't necessarily depend on lots of kernel help here. @@ -3317,10 +3577,12 @@ void __init console_init(void) */ static int __init printk_late_init(void) { + struct hlist_node *tmp; struct console *con; int ret; - for_each_console(con) { + console_list_lock(); + hlist_for_each_entry_safe(con, tmp, &console_list, node) { if (!(con->flags & CON_BOOT)) continue; @@ -3337,9 +3599,11 @@ static int __init printk_late_init(void) */ pr_warn("bootconsole [%s%d] uses init memory and must be disabled even before the real one is ready\n", con->name, con->index); - unregister_console(con); + unregister_console_locked(con); } } + console_list_unlock(); + ret = cpuhp_setup_state_nocalls(CPUHP_PRINTK_DEAD, "printk:dead", NULL, console_cpu_notify); WARN_ON(ret < 0); @@ -3359,6 +3623,7 @@ static bool __pr_flush(struct console *con, int timeout_ms, bool reset_on_progre struct console *c; u64 last_diff = 0; u64 printk_seq; + int cookie; u64 diff; u64 seq; @@ -3369,9 +3634,15 @@ static bool __pr_flush(struct console *con, int timeout_ms, bool reset_on_progre for (;;) { diff = 0; + /* + * Hold the console_lock to guarantee safe access to + * console->seq and to prevent changes to @console_suspended + * until all consoles have been processed. + */ console_lock(); - for_each_console(c) { + cookie = console_srcu_read_lock(); + for_each_console_srcu(c) { if (con && con != c) continue; if (!console_is_usable(c)) @@ -3380,6 +3651,7 @@ static bool __pr_flush(struct console *con, int timeout_ms, bool reset_on_progre if (printk_seq < seq) diff += seq - printk_seq; } + console_srcu_read_unlock(cookie); /* * If consoles are suspended, it cannot be expected that they diff --git a/kernel/printk/printk_ringbuffer.c b/kernel/printk/printk_ringbuffer.c index 2b7b6ddab4f7..2dc4d5a1f1ff 100644 --- a/kernel/printk/printk_ringbuffer.c +++ b/kernel/printk/printk_ringbuffer.c @@ -203,7 +203,7 @@ * prb_rec_init_wr(&r, 5); * * // try to extend, but only if it does not exceed 32 bytes - * if (prb_reserve_in_last(&e, &test_rb, &r, printk_caller_id()), 32) { + * if (prb_reserve_in_last(&e, &test_rb, &r, printk_caller_id(), 32)) { * snprintf(&r.text_buf[r.info->text_len], * r.text_buf_size - r.info->text_len, "hello"); * diff --git a/kernel/rcu/Kconfig b/kernel/rcu/Kconfig index 05106e6fbd0e..ab62074174c3 100644 --- a/kernel/rcu/Kconfig +++ b/kernel/rcu/Kconfig @@ -54,21 +54,17 @@ config RCU_EXPERT Say N if you are unsure. config SRCU - bool - help - This option selects the sleepable version of RCU. This version - permits arbitrary sleeping or blocking within RCU read-side critical - sections. + def_bool y config TINY_SRCU bool - default y if SRCU && TINY_RCU + default y if TINY_RCU help This option selects the single-CPU non-preemptible version of SRCU. config TREE_SRCU bool - default y if SRCU && !TINY_RCU + default y if !TINY_RCU help This option selects the full-fledged version of SRCU. @@ -77,7 +73,6 @@ config NEED_SRCU_NMI_SAFE config TASKS_RCU_GENERIC def_bool TASKS_RCU || TASKS_RUDE_RCU || TASKS_TRACE_RCU - select SRCU help This option enables generic infrastructure code supporting task-based RCU implementations. Not for manual selection. diff --git a/kernel/rcu/Kconfig.debug b/kernel/rcu/Kconfig.debug index 1b0c41d490f0..232e29fe3e5e 100644 --- a/kernel/rcu/Kconfig.debug +++ b/kernel/rcu/Kconfig.debug @@ -27,7 +27,6 @@ config RCU_SCALE_TEST tristate "performance tests for RCU" depends on DEBUG_KERNEL select TORTURE_TEST - select SRCU default n help This option provides a kernel module that runs performance @@ -43,7 +42,6 @@ config RCU_TORTURE_TEST tristate "torture tests for RCU" depends on DEBUG_KERNEL select TORTURE_TEST - select SRCU default n help This option provides a kernel module that runs torture tests @@ -59,7 +57,6 @@ config RCU_REF_SCALE_TEST tristate "Scalability tests for read-side synchronization (RCU and others)" depends on DEBUG_KERNEL select TORTURE_TEST - select SRCU default n help This option provides a kernel module that runs performance tests diff --git a/kernel/rcu/rcu.h b/kernel/rcu/rcu.h index 65704cbc9df7..c5aa934de59b 100644 --- a/kernel/rcu/rcu.h +++ b/kernel/rcu/rcu.h @@ -286,7 +286,7 @@ void rcu_test_sync_prims(void); */ extern void resched_cpu(int cpu); -#if defined(CONFIG_SRCU) || !defined(CONFIG_TINY_RCU) +#if !defined(CONFIG_TINY_RCU) #include @@ -375,6 +375,10 @@ extern void rcu_init_geometry(void); (cpu) <= rnp->grphi; \ (cpu) = rcu_find_next_bit((rnp), (cpu) + 1 - (rnp->grplo), (mask))) +#endif /* !defined(CONFIG_TINY_RCU) */ + +#if !defined(CONFIG_TINY_RCU) || defined(CONFIG_TASKS_RCU_GENERIC) + /* * Wrappers for the rcu_node::lock acquire and release. * @@ -437,7 +441,7 @@ do { \ #define raw_lockdep_assert_held_rcu_node(p) \ lockdep_assert_held(&ACCESS_PRIVATE(p, lock)) -#endif /* #if defined(CONFIG_SRCU) || !defined(CONFIG_TINY_RCU) */ +#endif // #if !defined(CONFIG_TINY_RCU) || defined(CONFIG_TASKS_RCU_GENERIC) #ifdef CONFIG_TINY_RCU /* Tiny RCU doesn't expedite, as its purpose in life is instead to be tiny. */ diff --git a/kernel/rcu/srcutiny.c b/kernel/rcu/srcutiny.c index 33adafdad261..b12fb0cec44d 100644 --- a/kernel/rcu/srcutiny.c +++ b/kernel/rcu/srcutiny.c @@ -197,6 +197,16 @@ void synchronize_srcu(struct srcu_struct *ssp) { struct rcu_synchronize rs; + RCU_LOCKDEP_WARN(lockdep_is_held(ssp) || + lock_is_held(&rcu_bh_lock_map) || + lock_is_held(&rcu_lock_map) || + lock_is_held(&rcu_sched_lock_map), + "Illegal synchronize_srcu() in same-type SRCU (or in RCU) read-side critical section"); + + if (rcu_scheduler_active == RCU_SCHEDULER_INACTIVE) + return; + + might_sleep(); init_rcu_head_on_stack(&rs.head); init_completion(&rs.completion); call_srcu(ssp, &rs.head, wakeme_after_rcu); diff --git a/kernel/rcu/update.c b/kernel/rcu/update.c index 738842c4886b..f5e6a2f95a2a 100644 --- a/kernel/rcu/update.c +++ b/kernel/rcu/update.c @@ -224,7 +224,7 @@ void rcu_test_sync_prims(void) synchronize_rcu_expedited(); } -#if !defined(CONFIG_TINY_RCU) || defined(CONFIG_SRCU) +#if !defined(CONFIG_TINY_RCU) /* * Switch to run-time mode once RCU has fully initialized. @@ -239,7 +239,7 @@ static int __init rcu_set_runtime_mode(void) } core_initcall(rcu_set_runtime_mode); -#endif /* #if !defined(CONFIG_TINY_RCU) || defined(CONFIG_SRCU) */ +#endif /* #if !defined(CONFIG_TINY_RCU) */ #ifdef CONFIG_DEBUG_LOCK_ALLOC static struct lock_class_key rcu_lock_key; @@ -559,10 +559,8 @@ static void early_boot_test_call_rcu(void) struct early_boot_kfree_rcu *rhp; call_rcu(&head, test_callback); - if (IS_ENABLED(CONFIG_SRCU)) { - early_srcu_cookie = start_poll_synchronize_srcu(&early_srcu); - call_srcu(&early_srcu, &shead, test_callback); - } + early_srcu_cookie = start_poll_synchronize_srcu(&early_srcu); + call_srcu(&early_srcu, &shead, test_callback); rhp = kmalloc(sizeof(*rhp), GFP_KERNEL); if (!WARN_ON_ONCE(!rhp)) kfree_rcu(rhp, rh); @@ -585,11 +583,9 @@ static int rcu_verify_early_boot_tests(void) if (rcu_self_test) { early_boot_test_counter++; rcu_barrier(); - if (IS_ENABLED(CONFIG_SRCU)) { - early_boot_test_counter++; - srcu_barrier(&early_srcu); - WARN_ON_ONCE(!poll_state_synchronize_srcu(&early_srcu, early_srcu_cookie)); - } + early_boot_test_counter++; + srcu_barrier(&early_srcu); + WARN_ON_ONCE(!poll_state_synchronize_srcu(&early_srcu, early_srcu_cookie)); } if (rcu_self_test_counter != early_boot_test_counter) { WARN_ON(1); diff --git a/lib/test_printf.c b/lib/test_printf.c index 5eb889679e4f..d6a5d4b5f884 100644 --- a/lib/test_printf.c +++ b/lib/test_printf.c @@ -692,31 +692,29 @@ flags(void) static void __init fwnode_pointer(void) { - const struct software_node softnodes[] = { - { .name = "first", }, - { .name = "second", .parent = &softnodes[0], }, - { .name = "third", .parent = &softnodes[1], }, - { NULL /* Guardian */ } - }; - const char * const full_name = "first/second/third"; + const struct software_node first = { .name = "first" }; + const struct software_node second = { .name = "second", .parent = &first }; + const struct software_node third = { .name = "third", .parent = &second }; + const struct software_node *group[] = { &first, &second, &third, NULL }; const char * const full_name_second = "first/second"; + const char * const full_name_third = "first/second/third"; const char * const second_name = "second"; const char * const third_name = "third"; int rval; - rval = software_node_register_nodes(softnodes); + rval = software_node_register_node_group(group); if (rval) { pr_warn("cannot register softnodes; rval %d\n", rval); return; } - test(full_name_second, "%pfw", software_node_fwnode(&softnodes[1])); - test(full_name, "%pfw", software_node_fwnode(&softnodes[2])); - test(full_name, "%pfwf", software_node_fwnode(&softnodes[2])); - test(second_name, "%pfwP", software_node_fwnode(&softnodes[1])); - test(third_name, "%pfwP", software_node_fwnode(&softnodes[2])); + test(full_name_second, "%pfw", software_node_fwnode(&second)); + test(full_name_third, "%pfw", software_node_fwnode(&third)); + test(full_name_third, "%pfwf", software_node_fwnode(&third)); + test(second_name, "%pfwP", software_node_fwnode(&second)); + test(third_name, "%pfwP", software_node_fwnode(&third)); - software_node_unregister_nodes(softnodes); + software_node_unregister_node_group(group); } static void __init fourcc_pointer(void) diff --git a/lib/vsprintf.c b/lib/vsprintf.c index 24f37bab8bc1..5b0611c00956 100644 --- a/lib/vsprintf.c +++ b/lib/vsprintf.c @@ -866,7 +866,7 @@ char *restricted_pointer(char *buf, char *end, const void *ptr, * kptr_restrict==1 cannot be used in IRQ context * because its test for CAP_SYSLOG would be meaningless. */ - if (in_irq() || in_serving_softirq() || in_nmi()) { + if (in_hardirq() || in_serving_softirq() || in_nmi()) { if (spec.field_width == -1) spec.field_width = 2 * sizeof(ptr); return error_string(buf, end, "pK-error", spec);