]> nv-tegra.nvidia Code Review - linux-2.6.git/commitdiff
oom: fix constraint deadlock
authorDavid Rientjes <rientjes@google.com>
Sun, 6 May 2007 21:50:00 +0000 (14:50 -0700)
committerLinus Torvalds <torvalds@woody.linux-foundation.org>
Mon, 7 May 2007 19:12:55 +0000 (12:12 -0700)
Fixes a deadlock in the OOM killer for allocations that are not

Before the OOM killer checks for the allocation constraint, it takes

constrained_alloc() iterates through each zone in the allocation zonelist
and calls cpuset_zone_allowed_softwall() to determine whether an allocation
for gfp_mask is possible.  If a zone's node is not in the OOM-triggering
task's mems_allowed, it is not exiting, and we did not fail on a
__GFP_HARDWALL allocation, cpuset_zone_allowed_softwall() attempts to take
callback_mutex to check the nearest exclusive ancestor of current's cpuset.
 This results in deadlock.

We now take callback_mutex after iterating through the zonelist since we
don't need it yet.

Cc: Andi Kleen <ak@suse.de>
Cc: Nick Piggin <npiggin@suse.de>
Cc: Christoph Lameter <clameter@engr.sgi.com>
Cc: Martin J. Bligh <mbligh@mbligh.org>
Signed-off-by: David Rientjes <rientjes@google.com>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

index 038d2234f13987dfcea3078ee8de2617ddca2f93..a7001410ab15964449f2b7188be3ecf05a9876eb 100644 (file)
@@ -399,6 +399,7 @@ void out_of_memory(struct zonelist *zonelist, gfp_t gfp_mask, int order)
        struct task_struct *p;
        unsigned long points = 0;
        unsigned long freed = 0;
+       int constraint;
        blocking_notifier_call_chain(&oom_notify_list, 0, &freed);
        if (freed > 0)
@@ -416,14 +417,15 @@ void out_of_memory(struct zonelist *zonelist, gfp_t gfp_mask, int order)
        if (sysctl_panic_on_oom == 2)
                panic("out of memory. Compulsory panic_on_oom is selected.\n");
-       cpuset_lock();
-       read_lock(&tasklist_lock);
         * Check if there were limitations on the allocation (only relevant for
         * NUMA) that may require different handling.
-       switch (constrained_alloc(zonelist, gfp_mask)) {
+       constraint = constrained_alloc(zonelist, gfp_mask);
+       cpuset_lock();
+       read_lock(&tasklist_lock);
+       switch (constraint) {
                oom_kill_process(current, points,
                                "No available memory (MPOL_BIND)");