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| author | Sergey Senozhatsky <sergey.senozhatsky@gmail.com> | 2017-01-21 13:47:29 +0300 |
|---|---|---|
| committer | Petr Mladek <pmladek@suse.com> | 2017-03-24 18:09:46 +0300 |
| commit | 64ca752dcbc018054bfea53b784d4c85d3ec896c (patch) | |
| tree | 8b11043b4bc3b6cf60a7297a951929a887236527 /kernel/printk/printk.c | |
| parent | 7d91de74436a69c2b78a7a72f1e7f97f8b4396fa (diff) | |
| download | linux-64ca752dcbc018054bfea53b784d4c85d3ec896c.tar.xz | |
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.
Link: http://lkml.kernel.org/r/20170121104729.8585-1-sergey.senozhatsky@gmail.com
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Diffstat (limited to 'kernel/printk/printk.c')
| -rw-r--r-- | kernel/printk/printk.c | 11 |
1 files changed, 6 insertions, 5 deletions
diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c index 34da86e73d00..94e2b104cdaa 100644 --- a/kernel/printk/printk.c +++ b/kernel/printk/printk.c @@ -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) { - console_lock(); - console_unlock(); + /* If trylock fails, someone else is doing the printing */ + if (console_trylock()) + console_unlock(); } return 0; } |