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printk: add pr_flush()
Provide a might-sleep function to allow waiting for console printers to catch up to the latest logged message. Use pr_flush() whenever it is desirable to get buffered messages printed before continuing: suspend_console(), resume_console(), console_stop(), console_start(), console_unblank(). Signed-off-by: John Ogness <john.ogness@linutronix.de> Reviewed-by: Petr Mladek <pmladek@suse.com> Signed-off-by: Petr Mladek <pmladek@suse.com> Link: https://lore.kernel.org/r/20220421212250.565456-12-john.ogness@linutronix.de
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@ -170,6 +170,8 @@ extern void __printk_safe_exit(void);
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#define printk_deferred_enter __printk_safe_enter
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#define printk_deferred_exit __printk_safe_exit
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extern bool pr_flush(int timeout_ms, bool reset_on_progress);
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/*
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* Please don't use printk_ratelimit(), because it shares ratelimiting state
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* with all other unrelated printk_ratelimit() callsites. Instead use
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@ -220,6 +222,11 @@ static inline void printk_deferred_exit(void)
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{
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}
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static inline bool pr_flush(int timeout_ms, bool reset_on_progress)
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{
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return true;
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}
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static inline int printk_ratelimit(void)
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{
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return 0;
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@ -2296,6 +2296,8 @@ asmlinkage __visible int _printk(const char *fmt, ...)
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}
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EXPORT_SYMBOL(_printk);
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static bool __pr_flush(struct console *con, int timeout_ms, bool reset_on_progress);
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#else /* CONFIG_PRINTK */
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#define CONSOLE_LOG_MAX 0
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@ -2328,6 +2330,7 @@ static void call_console_driver(struct console *con, const char *text, size_t le
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{
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}
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static bool suppress_message_printing(int level) { return false; }
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static bool __pr_flush(struct console *con, int timeout_ms, bool reset_on_progress) { return true; }
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#endif /* CONFIG_PRINTK */
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@ -2515,6 +2518,7 @@ void suspend_console(void)
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if (!console_suspend_enabled)
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return;
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pr_info("Suspending console(s) (use no_console_suspend to debug)\n");
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pr_flush(1000, true);
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console_lock();
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console_suspended = 1;
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up_console_sem();
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@ -2527,6 +2531,7 @@ void resume_console(void)
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down_console_sem();
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console_suspended = 0;
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console_unlock();
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pr_flush(1000, true);
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}
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/**
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@ -2912,6 +2917,9 @@ void console_unblank(void)
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if ((c->flags & CON_ENABLED) && c->unblank)
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c->unblank();
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console_unlock();
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if (!oops_in_progress)
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pr_flush(1000, true);
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}
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/**
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@ -2970,6 +2978,7 @@ struct tty_driver *console_device(int *index)
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*/
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void console_stop(struct console *console)
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{
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__pr_flush(console, 1000, true);
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console_lock();
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console->flags &= ~CON_ENABLED;
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console_unlock();
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@ -2981,6 +2990,7 @@ void console_start(struct console *console)
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console_lock();
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console->flags |= CON_ENABLED;
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console_unlock();
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__pr_flush(console, 1000, true);
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}
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EXPORT_SYMBOL(console_start);
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@ -3352,6 +3362,79 @@ static int __init printk_late_init(void)
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late_initcall(printk_late_init);
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#if defined CONFIG_PRINTK
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/* If @con is specified, only wait for that console. Otherwise wait for all. */
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static bool __pr_flush(struct console *con, int timeout_ms, bool reset_on_progress)
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{
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int remaining = timeout_ms;
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struct console *c;
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u64 last_diff = 0;
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u64 printk_seq;
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u64 diff;
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u64 seq;
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might_sleep();
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seq = prb_next_seq(prb);
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for (;;) {
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diff = 0;
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console_lock();
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for_each_console(c) {
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if (con && con != c)
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continue;
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if (!console_is_usable(c))
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continue;
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printk_seq = c->seq;
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if (printk_seq < seq)
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diff += seq - printk_seq;
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}
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console_unlock();
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if (diff != last_diff && reset_on_progress)
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remaining = timeout_ms;
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if (diff == 0 || remaining == 0)
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break;
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if (remaining < 0) {
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/* no timeout limit */
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msleep(100);
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} else if (remaining < 100) {
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msleep(remaining);
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remaining = 0;
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} else {
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msleep(100);
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remaining -= 100;
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}
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last_diff = diff;
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}
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return (diff == 0);
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}
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/**
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* pr_flush() - Wait for printing threads to catch up.
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*
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* @timeout_ms: The maximum time (in ms) to wait.
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* @reset_on_progress: Reset the timeout if forward progress is seen.
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*
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* A value of 0 for @timeout_ms means no waiting will occur. A value of -1
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* represents infinite waiting.
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*
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* If @reset_on_progress is true, the timeout will be reset whenever any
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* printer has been seen to make some forward progress.
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*
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* Context: Process context. May sleep while acquiring console lock.
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* Return: true if all enabled printers are caught up.
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*/
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bool pr_flush(int timeout_ms, bool reset_on_progress)
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{
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return __pr_flush(NULL, timeout_ms, reset_on_progress);
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}
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EXPORT_SYMBOL(pr_flush);
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/*
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* Delayed printk version, for scheduler-internal messages:
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*/
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