Messages in this thread | | | Date | Sun, 1 Mar 2009 18:00:15 +0100 | From | Nick Piggin <> | Subject | Re: recursive slqb_lock |
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On Sun, Mar 01, 2009 at 04:07:25PM +0100, Nick Piggin wrote: > On Thu, Feb 26, 2009 at 01:34:50PM +0800, Wu Fengguang wrote: > > Hi Nick, > > > > I got a lockdep warning. It looks like the slqb_lock will be taken > > twice in the call chain: > > > > s_start() => take slqb_lock > > s_show() > > gather_stats() => take slqb_lock again > > Hey, thanks for this. The following patch should fix it. > > -- > Fix the lockdep error reported by Fengguang where down_read slqb_lock > is taken twice, with the possibility for a deadlock. > > Signed-off-by: Nick Piggin <npiggin@suse.de> > --- > Index: linux-2.6/mm/slqb.c > =================================================================== > --- linux-2.6.orig/mm/slqb.c 2009-03-02 02:05:16.000000000 +1100 > +++ linux-2.6/mm/slqb.c 2009-03-02 02:05:45.000000000 +1100 > @@ -3079,7 +3079,9 @@ static void __gather_stats(void *arg) > spin_unlock(&gather->lock); > } > > -static void gather_stats(struct kmem_cache *s, struct stats_gather *stats) > +/* must be called with slqb_lock held */ > +static void gather_stats_locked(struct kmem_cache *s, > + struct stats_gather *stats) > { > #ifdef CONFIG_NUMA > int node; > @@ -3089,8 +3091,6 @@ static void gather_stats(struct kmem_cac > stats->s = s; > spin_lock_init(&stats->lock); > > - down_read(&slqb_lock); /* hold off hotplug */ > - > on_each_cpu(__gather_stats, stats, 1); > > #ifdef CONFIG_NUMA > @@ -3119,10 +3119,15 @@ static void gather_stats(struct kmem_cac > } > #endif > > - up_read(&slqb_lock); > - > stats->nr_objects = stats->nr_slabs * s->objects; > } > + > +static void gather_stats(struct kmem_cache *s, struct stats_gather *stats) > +{ > + down_read(&slqb_lock); /* hold off hotplug */ > + gather_stats(s, stats); > + up_read(&slqb_lock); > +}
Oops, I didn't test it. That call should be to gather_stats_locked of course.
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