> 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 <kamezawa.hiroyu@xxxxxxxxxxxxxx> > Signed-off-by: David Rientjes <rientjes@xxxxxxxxxx> ack. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>