| Message ID | 1427264236-17249-6-git-send-email-hannes@cmpxchg.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Wed 25-03-15 02:17:09, Johannes Weiner wrote: > It turns out that the mechanism to wait for exiting OOM victims is > less generic than it looks: it won't issue wakeups unless the OOM > killer is disabled. > > The reason this check was added was the thought that, since only the > OOM disabling code would wait on this queue, wakeup operations could > be saved when that specific consumer is known to be absent. > > However, this is quite the handgrenade. Later attempts to reuse the > waitqueue for other purposes will lead to completely unexpected bugs > and the failure mode will appear seemingly illogical. Generally, > providers shouldn't make unnecessary assumptions about consumers. > > This could have been replaced with waitqueue_active(), but it only > saves a few instructions in one of the coldest paths in the kernel. > Simply remove it. > > Signed-off-by: Johannes Weiner <hannes@cmpxchg.org> Acked-by: Michal Hocko <mhocko@suse.cz> > --- > mm/oom_kill.c | 6 +----- > 1 file changed, 1 insertion(+), 5 deletions(-) > > diff --git a/mm/oom_kill.c b/mm/oom_kill.c > index 88aa9ba40fa5..d3490b019d46 100644 > --- a/mm/oom_kill.c > +++ b/mm/oom_kill.c > @@ -437,11 +437,7 @@ void exit_oom_victim(void) > { > clear_thread_flag(TIF_MEMDIE); > > - /* > - * There is no need to signal the lasst oom_victim if there > - * is nobody who cares. > - */ > - if (!atomic_dec_return(&oom_victims) && oom_killer_disabled) > + if (!atomic_dec_return(&oom_victims)) > wake_up_all(&oom_victims_wait); > } > > -- > 2.3.3 >
diff --git a/mm/oom_kill.c b/mm/oom_kill.c index 88aa9ba40fa5..d3490b019d46 100644 --- a/mm/oom_kill.c +++ b/mm/oom_kill.c @@ -437,11 +437,7 @@ void exit_oom_victim(void) { clear_thread_flag(TIF_MEMDIE); - /* - * There is no need to signal the lasst oom_victim if there - * is nobody who cares. - */ - if (!atomic_dec_return(&oom_victims) && oom_killer_disabled) + if (!atomic_dec_return(&oom_victims)) wake_up_all(&oom_victims_wait); }
It turns out that the mechanism to wait for exiting OOM victims is less generic than it looks: it won't issue wakeups unless the OOM killer is disabled. The reason this check was added was the thought that, since only the OOM disabling code would wait on this queue, wakeup operations could be saved when that specific consumer is known to be absent. However, this is quite the handgrenade. Later attempts to reuse the waitqueue for other purposes will lead to completely unexpected bugs and the failure mode will appear seemingly illogical. Generally, providers shouldn't make unnecessary assumptions about consumers. This could have been replaced with waitqueue_active(), but it only saves a few instructions in one of the coldest paths in the kernel. Simply remove it. Signed-off-by: Johannes Weiner <hannes@cmpxchg.org> --- mm/oom_kill.c | 6 +----- 1 file changed, 1 insertion(+), 5 deletions(-)