lkml.org 
[lkml]   [2022]   [May]   [13]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH v4] random: use static branch for crng_ready()
Am Thu, May 12, 2022 at 06:37:48PM +0200 schrieb Jason A. Donenfeld:
> Since crng_ready() is only false briefly during initialization and then
> forever after becomes true, we don't need to evaluate it after, making
> it a prime candidate for a static branch.
>
> One complication, however, is that it changes state in a particular call
> to credit_init_bits(), which might be made from atomic context, which
> means we must kick off a workqueue to change the static key. Further
> complicating things, credit_init_bits() may be called sufficiently early
> on in system initialization such that system_wq is NULL.
>
> Fortunately, there exists the nice function execute_in_process_context(),
> which will immediately execute the function if !in_interrupt(), and
> otherwise defer it to a workqueue. During early init, before workqueues
> are available, in_interrupt() is always false, because interrupts
> haven't even been enabled yet, which means the function in that case
> executes immediately. Later on, after workqueues are available,
> in_interrupt() might be true, but in that case, the work is queued in
> system_wq and all goes well.

Reviewed-by: Dominik Brodowski <linux@dominikbrodowski.net>

Thanks,
Dominik

\
 
 \ /
  Last update: 2022-05-13 08:28    [W:0.053 / U:0.404 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site