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printk: __pr_flush: use srcu console list iterator

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Use srcu console list iteration for console list traversal.

Document why the console_lock is still necessary. Note that this
is a preparatory change for when console_lock no longer provides
synchronization for the console list.

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/20221116162152.193147-17-john.ogness@linutronix.de
This commit is contained in:
John Ogness 2022-11-16 17:27:28 +01:06 committed by Petr Mladek
parent fc956ae0de
commit eb7f1ed250
1 changed files with 9 additions and 1 deletions
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10
kernel/printk/printk.c
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@ -3561,6 +3561,7 @@ 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;
@ -3571,9 +3572,15 @@ 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))
@ -3582,6 +3589,7 @@ 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