path: root/mm/oom_kill.c
diff options
authorDavid Rientjes <>2010-08-09 17:18:48 -0700
committerLinus Torvalds <>2010-08-09 20:44:56 -0700
commit7b98c2e402eaa1f2beec18b1bde17f74948a19db (patch)
treea0d3920f84e981cca5be386e2cc5a6320c4d8bdc /mm/oom_kill.c
parentc81fac5cb8c92b8b4795ac250a46c7514d1fce06 (diff)
oom: give current access to memory reserves if it has been killed
It's possible to livelock the page allocator if a thread has mm->mmap_sem and fails to make forward progress because the oom killer selects another thread sharing the same ->mm to kill that cannot exit until the semaphore is dropped. The oom killer will not kill multiple tasks at the same time; each oom killed task must exit before another task may be killed. Thus, if one thread is holding mm->mmap_sem and cannot allocate memory, all threads sharing the same ->mm are blocked from exiting as well. In the oom kill case, that means the thread holding mm->mmap_sem will never free additional memory since it cannot get access to memory reserves and the thread that depends on it with access to memory reserves cannot exit because it cannot acquire the semaphore. Thus, the page allocators livelocks. When the oom killer is called and current happens to have a pending SIGKILL, this patch automatically gives it access to memory reserves and returns. Upon returning to the page allocator, its allocation will hopefully succeed so it can quickly exit and free its memory. If not, the page allocator will fail the allocation if it is not __GFP_NOFAIL. Reviewed-by: KAMEZAWA Hiroyuki <> Signed-off-by: David Rientjes <> Cc: KOSAKI Motohiro <> Signed-off-by: Andrew Morton <> Signed-off-by: Linus Torvalds <>
Diffstat (limited to 'mm/oom_kill.c')
1 files changed, 10 insertions, 0 deletions
diff --git a/mm/oom_kill.c b/mm/oom_kill.c
index 907e2c0ad7a6..64cdacad83d9 100644
--- a/mm/oom_kill.c
+++ b/mm/oom_kill.c
@@ -645,6 +645,16 @@ void out_of_memory(struct zonelist *zonelist, gfp_t gfp_mask,
/* Got some memory back in the last second. */
+ /*
+ * If current has a pending SIGKILL, then automatically select it. The
+ * goal is to allow it to allocate so that it may quickly exit and free
+ * its memory.
+ */
+ if (fatal_signal_pending(current)) {
+ set_thread_flag(TIF_MEMDIE);
+ return;
+ }
if (sysctl_panic_on_oom == 2) {
dump_header(NULL, gfp_mask, order, NULL);
panic("out of memory. Compulsory panic_on_oom is selected.\n");