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printk: flush consoles before checking progress

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Commit 9e70a5e109 ("printk: Add per-console suspended state")
removed console lock usage during resume and replaced it with
the clearly defined console_list_lock and srcu mechanisms.

However, the console lock usage had an important side-effect
of flushing the consoles. After its removal, consoles were no
longer flushed before checking their progress.

Add the console_lock/console_unlock dance to the beginning
of __pr_flush() to actually flush the consoles before checking
their progress. Also add comments to clarify this additional
usage of the console lock.

Note that console_unlock() does not guarantee flushing all messages
since the commit dbdda842fe ("printk: Add console owner and waiter
logic to load balance console writes").

Reported-by: Todd Brandt <todd.e.brandt@intel.com>
Closes: https://bugzilla.kernel.org/show_bug.cgi?id=217955
Fixes: 9e70a5e109 ("printk: Add per-console suspended state")
Co-developed-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Link: https://lore.kernel.org/r/20231006082151.6969-2-pmladek@suse.com
This commit is contained in:
John Ogness 2023-10-06 10:21:50 +02:00 committed by Petr Mladek
parent 132a90d152
commit 054c22bd78
1 changed files with 7 additions and 1 deletions
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8
kernel/printk/printk.c
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@ -3738,12 +3738,18 @@ static bool __pr_flush(struct console *con, int timeout_ms, bool reset_on_progre
seq = prb_next_seq(prb);
/* Flush the consoles so that records up to @seq are printed. */
console_lock();
console_unlock();
for (;;) {
diff = 0;
/*
* Hold the console_lock to guarantee safe access to
* console->seq.
* console->seq. Releasing console_lock flushes more
* records in case @seq is still not printed on all
* usable consoles.
*/
console_lock();