Messages in this thread Patch in this message | | | From | John Ogness <> | Subject | [PATCH printk v1 08/13] printk: add pr_flush() | Date | Mon, 7 Feb 2022 20:49:18 +0106 |
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Provide a might-sleep function to allow waiting for threaded 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> --- include/linux/printk.h | 7 ++++ kernel/printk/printk.c | 73 +++++++++++++++++++++++++++++++++++++++++- 2 files changed, 79 insertions(+), 1 deletion(-)
diff --git a/include/linux/printk.h b/include/linux/printk.h index cd8192e611a1..6596f02d1f05 100644 --- a/include/linux/printk.h +++ b/include/linux/printk.h @@ -170,6 +170,8 @@ extern void __printk_safe_exit(void); #define printk_deferred_enter __printk_safe_enter #define printk_deferred_exit __printk_safe_exit +extern bool pr_flush(int timeout_ms, bool reset_on_progress); + /* * Please don't use printk_ratelimit(), because it shares ratelimiting state * with all other unrelated printk_ratelimit() callsites. Instead use @@ -224,6 +226,11 @@ static inline void printk_deferred_exit(void) { } +static inline bool pr_flush(int timeout_ms, bool reset_on_progress) +{ + return true; +} + static inline int printk_ratelimit(void) { return 0; diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c index 02bde45c1149..1e80fd052bd5 100644 --- a/kernel/printk/printk.c +++ b/kernel/printk/printk.c @@ -2449,6 +2449,7 @@ void suspend_console(void) if (!console_suspend_enabled) return; pr_info("Suspending console(s) (use no_console_suspend to debug)\n"); + pr_flush(1000, true); console_lock(); console_suspended = 1; up_console_sem(); @@ -2461,6 +2462,7 @@ void resume_console(void) down_console_sem(); console_suspended = 0; console_unlock(); + pr_flush(1000, true); } /** @@ -2802,8 +2804,10 @@ void console_unblank(void) if (oops_in_progress) { if (down_trylock_console_sem() != 0) return; - } else + } else { + pr_flush(1000, true); console_lock(); + } console_locked = 1; console_may_schedule = 0; @@ -2869,6 +2873,7 @@ struct tty_driver *console_device(int *index) */ void console_stop(struct console *console) { + pr_flush(1000, true); console_lock(); console->flags &= ~CON_ENABLED; console_unlock(); @@ -2880,6 +2885,7 @@ void console_start(struct console *console) console_lock(); console->flags |= CON_ENABLED; console_unlock(); + pr_flush(1000, true); } EXPORT_SYMBOL(console_start); @@ -3249,6 +3255,71 @@ static int __init printk_late_init(void) late_initcall(printk_late_init); #if defined CONFIG_PRINTK +/** + * pr_flush() - Wait for printing threads to catch up. + * + * @timeout_ms: The maximum time (in ms) to wait. + * @reset_on_progress: Reset the timeout if forward progress is seen. + * + * A value of 0 for @timeout_ms means no waiting will occur. A value of -1 + * represents infinite waiting. + * + * If @reset_on_progress is true, the timeout will be reset whenever any + * printer has been seen to make some forward progress. + * + * Context: Process context. May sleep while acquiring console lock. + * Return: true if all enabled printers are caught up. + */ +bool pr_flush(int timeout_ms, bool reset_on_progress) +{ + int remaining = timeout_ms; + struct console *con; + u64 last_diff = 0; + u64 printk_seq; + u64 diff; + u64 seq; + + might_sleep(); + + seq = prb_next_seq(prb); + + for (;;) { + diff = 0; + + console_lock(); + for_each_console(con) { + if (!console_is_usable(con)) + continue; + printk_seq = con->seq; + if (printk_seq < seq) + diff += seq - printk_seq; + } + console_unlock(); + + if (diff != last_diff && reset_on_progress) + remaining = timeout_ms; + + if (diff == 0 || remaining == 0) + break; + + if (remaining < 0) { + /* no timeout limit */ + msleep(100); + } else if (remaining < 100) { + msleep(remaining); + remaining = 0; + } else { + msleep(100); + remaining -= 100; + } + + last_diff = diff; + } + + return (diff == 0); +} +EXPORT_SYMBOL(pr_flush); + /* * Delayed printk version, for scheduler-internal messages: */ -- 2.30.2
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