mirror of
https://github.com/torvalds/linux
synced 2024-10-18 01:08:35 +00:00
589f892ac8
The uart_ops startup() callback is called without interrupts
disabled and without port->lock locked, relatively late during the
boot process (from the call path of console_on_rootfs()). If the
device is a console, it was already previously registered and could
be actively printing messages.
Since the startup() callback is reading/writing registers used by
the console write() callback (AML_UART_CONTROL), its access must
be synchronized using the port->lock. Currently it is not.
The startup() callback is the only function that explicitly enables
interrupts. Without the synchronization, it is possible that
interrupts become accidentally permanently disabled.
CPU0 CPU1
meson_serial_console_write meson_uart_startup
-------------------------- ------------------
spin_lock(port->lock)
val = readl(AML_UART_CONTROL)
uart_console_write()
writel(INT_EN, AML_UART_CONTROL)
writel(val, AML_UART_CONTROL)
spin_unlock(port->lock)
Add port->lock synchronization to meson_uart_startup() to avoid
racing with meson_serial_console_write().
Also add detailed comments to meson_uart_reset() explaining why it
is *not* using port->lock synchronization.
Link: https://lore.kernel.org/lkml/2a82eae7-a256-f70c-fd82-4e510750906e@samsung.com
Fixes:
|
||
|---|---|---|
| .. | ||
| hvc | ||
| ipwireless | ||
| serdev | ||
| serial | ||
| vt | ||
| amiserial.c | ||
| ehv_bytechan.c | ||
| goldfish.c | ||
| Kconfig | ||
| Makefile | ||
| mips_ejtag_fdc.c | ||
| moxa.c | ||
| mxser.c | ||
| n_gsm.c | ||
| n_hdlc.c | ||
| n_null.c | ||
| n_tty.c | ||
| nozomi.c | ||
| pty.c | ||
| rpmsg_tty.c | ||
| synclink_gt.c | ||
| sysrq.c | ||
| tty.h | ||
| tty_audit.c | ||
| tty_baudrate.c | ||
| tty_buffer.c | ||
| tty_io.c | ||
| tty_ioctl.c | ||
| tty_jobctrl.c | ||
| tty_ldisc.c | ||
| tty_ldsem.c | ||
| tty_mutex.c | ||
| tty_port.c | ||
| ttynull.c | ||
| vcc.c | ||