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Message-ID: <20090302064735.GA1257@wotan.suse.de>
Date: Mon, 2 Mar 2009 07:47:36 +0100
From: Nick Piggin <npiggin@...e.de>
To: Pekka Enberg <penberg@...helsinki.fi>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Cc: Wu Fengguang <fengguang.wu@...el.com>
Subject: [patch 1/2] slqb: fix deadlock
Fix the lockdep error reported by Fengguang where down_read slqb_lock
is taken twice when reading /proc/slabinfo, with the possibility for a
deadlock.
Cc: Wu Fengguang <fengguang.wu@...el.com>
Signed-off-by: Nick Piggin <npiggin@...e.de>
---
Index: linux-2.6/mm/slqb.c
===================================================================
--- linux-2.6.orig/mm/slqb.c 2009-03-02 17:42:09.000000000 +1100
+++ linux-2.6/mm/slqb.c 2009-03-02 17:44:10.000000000 +1100
@@ -3075,7 +3075,9 @@ 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;
@@ -3085,8 +3087,6 @@ 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
@@ -3115,10 +3115,15 @@ 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_locked(s, stats);
+ up_read(&slqb_lock);
+}
#endif
/*
@@ -3171,7 +3176,7 @@ static int s_show(struct seq_file *m, vo
s = list_entry(p, struct kmem_cache, list);
- gather_stats(s, &stats);
+ gather_stats_locked(s, &stats);
seq_printf(m, "%-17s %6lu %6lu %6u %4u %4d", s->name, stats.nr_inuse,
stats.nr_objects, s->size, s->objects, (1 << s->order));
--
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