Messages in this thread | | | Date | Tue, 16 Feb 2016 15:43:06 +0100 | From | Petr Mladek <> | Subject | Re: [PATCH v4 2/3] printk: set may_schedule for some of console_trylock callers |
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On Sat 2016-02-13 03:37:11, Sergey Senozhatsky wrote: > console_unlock() allows to cond_resched() if its caller has > set `console_may_schedule' to 1, since > 'commit 8d91f8b15361 ("printk: do cond_resched() between lines while > outputting to consoles")'. > > The rules are: > -- console_lock() always sets `console_may_schedule' to 1 > -- console_trylock() always sets `console_may_schedule' to 0 > > However, console_trylock() callers (among them is printk()) do > not always call printk() from atomic contexts, and some of them > can cond_resched() in console_unlock(), so console_trylock() > can set `console_may_schedule' to 1 for such processes. > > For !CONFIG_PREEMPT_COUNT kernels, however, console_trylock() > always sets `console_may_schedule' to 0. > > It's possible to drop explicit preempt_disable()/preempt_enable() > in vprintk_emit(), because console_unlock() and console_trylock() > are now smart enough: > a) console_unlock() does not cond_resched() when it's unsafe > (console_trylock() takes care of that) > b) console_unlock() does can_use_console() check. > > Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
It looks safe after all.
Reviewed-by: Petr Mladek <pmladek@suse.com>
Best Regards, Petr
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