Commit 64ca752d authored by Sergey Senozhatsky's avatar Sergey Senozhatsky Committed by Petr Mladek
Browse files

printk: use console_trylock() in console_cpu_notify()

There is no need to always call blocking console_lock() in
console_cpu_notify(), it's quite possible that console_sem can
be locked by other CPU on the system, either already printing
or soon to begin printing the messages. console_lock() in this
case can simply block CPU hotplug for unknown period of time
(console_unlock() is time unbound). Not that hotplug is very
fast, but still, with other CPUs being online and doing
printk() console_cpu_notify() can stuck.

Use console_trylock() instead and opt-out if console_sem is
already acquired from another CPU, since that CPU will do
the printing for us.


Cc: Steven Rostedt <>
Cc: Andrew Morton <>
Cc: Thomas Gleixner <>
Cc: Sebastian Andrzej Siewior <>
Cc: Ingo Molnar <>
Signed-off-by: default avatarSergey Senozhatsky <>
Signed-off-by: default avatarPetr Mladek <>
parent 7d91de74
......@@ -2028,15 +2028,16 @@ void resume_console(void)
* @cpu: unused
* If printk() is called from a CPU that is not online yet, the messages
* will be spooled but will not show up on the console. This function is
* called when a new CPU comes online (or fails to come up), and ensures
* that any such output gets printed.
* will be printed on the console only if there are CON_ANYTIME consoles.
* This function is called when a new CPU comes online (or fails to come
* up) or goes offline.
static int console_cpu_notify(unsigned int cpu)
if (!cpuhp_tasks_frozen) {
/* If trylock fails, someone else is doing the printing */
if (console_trylock())
return 0;
Markdown is supported
0% or .
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment