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printk: console_unblank: use srcu console list iterator 

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/20221116162152.193147-19-john.ogness@linutronix.de
This commit is contained in:
John Ogness 2022-11-16 17:27:30 +01:06 committed by Petr Mladek
parent 12f1da5fc4
commit d792db6f6b
1 changed files with 13 additions and 4 deletions
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17
kernel/printk/printk.c
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@ -3000,10 +3000,14 @@ EXPORT_SYMBOL(console_conditional_schedule);
void console_unblank(void) void console_unblank(void)
{ {
struct console *c; struct console *c;
int cookie;
/* /*
* console_unblank can no longer be called in interrupt context unless * Stop console printing because the unblank() callback may
* oops_in_progress is set to 1.. * assume the console is not within its write() callback.
*
* If @oops_in_progress is set, this may be an atomic context.
* In that case, attempt a trylock as best-effort.
*/ */
if (oops_in_progress) { if (oops_in_progress) {
if (down_trylock_console_sem() != 0) if (down_trylock_console_sem() != 0)
@ -3013,9 +3017,14 @@ void console_unblank(void)
console_locked = 1; console_locked = 1;
console_may_schedule = 0; console_may_schedule = 0;
for_each_console(c)
if ((c->flags & CON_ENABLED) && c->unblank) cookie = console_srcu_read_lock();
for_each_console_srcu(c) {
if ((console_srcu_read_flags(c) & CON_ENABLED) && c->unblank)
c->unblank(); c->unblank();
}
console_srcu_read_unlock(cookie);
console_unlock(); console_unlock();
if (!oops_in_progress) if (!oops_in_progress)