Michal Hocko wrote:
> On Wed 25-10-17 23:58:33, Tetsuo Handa wrote:
> > I thought something like
> >
> > --- a/mm/page_alloc.c
> > +++ b/mm/page_alloc.c
> > @@ -3872,6 +3872,7 @@ bool gfp_pfmemalloc_allowed(gfp_t gfp_mask)
> > unsigned int stall_timeout = 10 * HZ;
> > unsigned int cpuset_mems_cookie;
> > int reserve_flags;
> > + static DEFINE_MUTEX(warn_lock);
> >
> > /*
> > * In the slowpath, we sanity check order to avoid ever trying to
> > @@ -4002,11 +4003,15 @@ bool gfp_pfmemalloc_allowed(gfp_t gfp_mask)
> > goto nopage;
> >
> > /* Make sure we know about allocations which stall for too long */
> > - if (time_after(jiffies, alloc_start + stall_timeout)) {
> > - warn_alloc(gfp_mask & ~__GFP_NOWARN, ac->nodemask,
> > - "page allocation stalls for %ums, order:%u",
> > - jiffies_to_msecs(jiffies-alloc_start), order);
> > - stall_timeout += 10 * HZ;
> > + if (time_after(jiffies, alloc_start + stall_timeout) &&
> > + mutex_trylock(&warn_lock)) {
> > + if (!mutex_is_locked(&oom_lock)) {
>
> The check for oom_lock just doesn't make any sense. The lock can be take
> at any time after the check.
The check for oom_lock is optimistic. If we go pessimistic, we will
need to use oom_printk_lock, but you don't like oom_printk_lock, do you?
Anyway, let's remove warn_alloc().
>
> > + warn_alloc(gfp_mask & ~__GFP_NOWARN, ac->nodemask,
> > + "page allocation stalls for %ums, order:%u",
> > + jiffies_to_msecs(jiffies-alloc_start), order);
> > + stall_timeout += 10 * HZ;
> > + }
> > + mutex_unlock(&warn_lock);
> > }
> >
> > /* Avoid recursion of direct reclaim */
> >
> > for isolating the OOM killer messages and the stall warning messages (in order to
> > break continuation condition in console_unlock()), and
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