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authorDavid Rientjes <rientjes@google.com>2007-05-06 14:50:00 -0700
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2007-05-07 12:12:55 -0700
commit2b45ab3398a0ba119b1f672c7c56fd5a431b7f0a (patch)
tree302238b786d2137111244702345acf6d4a17d4b7
parent2b744c01a54fe0c9974ff1b29522f25f07084053 (diff)
oom: fix constraint deadlock
Fixes a deadlock in the OOM killer for allocations that are not __GFP_HARDWALL. Before the OOM killer checks for the allocation constraint, it takes callback_mutex. 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>
-rw-r--r--mm/oom_kill.c10
1 files changed, 6 insertions, 4 deletions
diff --git a/mm/oom_kill.c b/mm/oom_kill.c
index 038d2234f139..a7001410ab15 100644
--- a/mm/oom_kill.c
+++ b/mm/oom_kill.c
@@ -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) {
case CONSTRAINT_MEMORY_POLICY:
oom_kill_process(current, points,
"No available memory (MPOL_BIND)");

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