lkml.org 
[lkml]   [2016]   [Jan]   [6]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH 1/2] kernel, timekeeping, add trylock option to ktime_get_with_offset()
On Wed, Jan 06, 2016 at 08:00:33AM -0500, Prarit Bhargava wrote:
> -ktime_t ktime_get_with_offset(enum tk_offsets offs)
> +ktime_t ktime_get_with_offset(enum tk_offsets offs, int trylock)
> {
> struct timekeeper *tk = &tk_core.timekeeper;
> unsigned int seq;
> ktime_t base, *offset = offsets[offs];
> s64 nsecs;
> + unsigned long flags = 0;
> +
> + if (unlikely(!timekeeping_initialized))
> + return ktime_set(0, 0);
>
> WARN_ON(timekeeping_suspended);
>
> + if (trylock && !raw_spin_trylock_irqsave(&timekeeper_lock, flags))
> + return ktime_set(KTIME_MAX, 0);
> +

Are you trying to avoid a deadlock caused by calling printk() with
timekeeper_lock locked?

I believe this is already unsafe, as explained in the commit log
of 6d9bcb62 (timekeeping: use printk_deferred when holding
timekeeping seqlock).

So directly calling ktime_get() from printk would just turn a
rare deadlock into a certain one - perhaps a good thing?


--
Jiri Bohac <jbohac@suse.cz>
SUSE Labs, SUSE CZ



\
 
 \ /
  Last update: 2016-01-06 17:21    [W:0.189 / U:3.356 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site