From 2b45ab3398a0ba119b1f672c7c56fd5a431b7f0a Mon Sep 17 00:00:00 2001 From: David Rientjes Date: Sun, 6 May 2007 14:50:00 -0700 Subject: [PATCH] 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 Cc: Nick Piggin Cc: Christoph Lameter Cc: Martin J. Bligh Signed-off-by: David Rientjes Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/oom_kill.c | 10 ++++++---- 1 file 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)"); -- 2.20.1