From 505970b96e3b7d22177c38e03435a68376628e7a Mon Sep 17 00:00:00 2001 From: Paul Jackson Date: Sat, 14 Jan 2006 13:21:06 -0800 Subject: [PATCH] cpuset oom lock fix The problem, reported in: http://bugzilla.kernel.org/show_bug.cgi?id=5859 and by various other email messages and lkml posts is that the cpuset hook in the oom (out of memory) code can try to take a cpuset semaphore while holding the tasklist_lock (a spinlock). One must not sleep while holding a spinlock. The fix seems easy enough - move the cpuset semaphore region outside the tasklist_lock region. This required a few lines of mechanism to implement. The oom code where the locking needs to be changed does not have access to the cpuset locks, which are internal to kernel/cpuset.c only. So I provided a couple more cpuset interface routines, available to the rest of the kernel, which simple take and drop the lock needed here (cpusets callback_sem). Signed-off-by: Paul Jackson Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/oom_kill.c | 3 +++ 1 file changed, 3 insertions(+) (limited to 'mm/oom_kill.c') diff --git a/mm/oom_kill.c b/mm/oom_kill.c index 4748b906aff2..14bd4ec79597 100644 --- a/mm/oom_kill.c +++ b/mm/oom_kill.c @@ -274,6 +274,7 @@ void out_of_memory(gfp_t gfp_mask, int order) show_mem(); } + cpuset_lock(); read_lock(&tasklist_lock); retry: p = select_bad_process(); @@ -284,6 +285,7 @@ retry: /* Found nothing?!?! Either we hang forever, or we panic. */ if (!p) { read_unlock(&tasklist_lock); + cpuset_unlock(); panic("Out of memory and no killable processes...\n"); } @@ -293,6 +295,7 @@ retry: out: read_unlock(&tasklist_lock); + cpuset_unlock(); if (mm) mmput(mm); -- cgit v1.2.3-55-g7522