Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > linux.kernel > #1335476

Re: [PATCH v4 2/3] printk: set may_schedule for some of console_trylock callers

Show all headers | View raw

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

Back to linux.kernel | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread

Thread

[PATCH v4 0/2] let printk()/console_trylock() callers to cond_resched() Sergey Senozhatsky <sergey.senozhatsky@gmail.com> - 2016-02-12 19:40 +0100
  [PATCH v4 3/3] printk: check CON_ENABLED in have_callable_console() Sergey Senozhatsky <sergey.senozhatsky@gmail.com> - 2016-02-12 19:40 +0100
    Re: [PATCH v4 3/3] printk: check CON_ENABLED in  have_callable_console() Petr Mladek <pmladek@suse.com> - 2016-02-16 15:50 +0100
      Re: [PATCH v4 3/3] printk: check CON_ENABLED in  have_callable_console() Sergey Senozhatsky <sergey.senozhatsky@gmail.com> - 2016-02-16 16:50 +0100
  [PATCH v4 2/3] printk: set may_schedule for some of console_trylock callers Sergey Senozhatsky <sergey.senozhatsky@gmail.com> - 2016-02-12 19:40 +0100
    Re: [PATCH v4 2/3] printk: set may_schedule for some of  console_trylock callers Petr Mladek <pmladek@suse.com> - 2016-02-16 15:50 +0100
      Re: [PATCH v4 2/3] printk: set may_schedule for some of  console_trylock callers Sergey Senozhatsky <sergey.senozhatsky@gmail.com> - 2016-02-16 16:50 +0100

csiph-web