I managed to get the stack trace for the process that refuses to die. I am not sure it's due to the deadlock described in earlier messages. I will investigate further. [96283.704390] chrome x 815ecd20 0 16573 1112 0x00100104 [96283.704405] c107fe34 00200046 f57ae000 815ecd20 815ecd20 ec0b645a 0000578f f67cfd20 [96283.704427] d0a9a9a0 c107fdf8 81037be5 f5bdf1e8 f6021800 00000000 c107fe04 00200202 [96283.704449] c107fe0c 00200202 f5bdf1b0 c107fe24 8117ddb1 00200202 f5bdf1b0 f5bdf1b8 [96283.704471] Call Trace: [96283.704484] [<81037be5>] ? queue_work_on+0x2d/0x39 [96283.704497] [<8117ddb1>] ? put_io_context+0x52/0x6a [96283.704510] [<813b68f6>] schedule+0x56/0x58 [96283.704520] [<81028525>] do_exit+0x63e/0x640 [96283.704530] [<81028752>] do_group_exit+0x63/0x86 [96283.704541] [<81032b19>] get_signal_to_deliver+0x434/0x44b [96283.704554] [<81001e01>] do_signal+0x37/0x4fe [96283.704564] [<8103e31d>] ? update_rmtp+0x67/0x67 [96283.704585] [<8105622a>] ? clockevents_program_event+0xea/0x108 [96283.704599] [<81050d92>] ? timekeeping_get_ns+0x11/0x55 [96283.704610] [<8105a758>] ? sys_futex+0xcb/0xdb [96283.704620] [<810024a7>] do_notify_resume+0x26/0x65 [96283.704632] [<813b7305>] work_notifysig+0xa/0x11 [96283.704644] [<813b0000>] ? coretemp_cpu_callback+0x88/0x179 On Mon, Oct 22, 2012 at 11:03 PM, David Rientjes <rientjes@xxxxxxxxxx> wrote: > On Tue, 23 Oct 2012, Minchan Kim wrote: > >> > I found the source, and maybe the cause, of the problem I am >> > experiencing when running out of memory with zram enabled. It may be >> > a known problem. The OOM killer doesn't find any killable process >> > because select_bad_process() keeps returning -1 here: >> > >> > /* >> > * This task already has access to memory reserves and is >> > * being killed. Don't allow any other task access to the >> > * memory reserve. >> > * >> > * Note: this may have a chance of deadlock if it gets >> > * blocked waiting for another task which itself is waiting >> > * for memory. Is there a better alternative? >> > */ >> > if (test_tsk_thread_flag(p, TIF_MEMDIE)) { >> > if (unlikely(frozen(p))) >> > __thaw_task(p); >> > if (!force_kill) >> > return ERR_PTR(-1UL); >> > } >> > >> > select_bad_process() is called by out_of_memory() in __alloc_page_may_oom(). >> >> I think it's not a zram problem but general problem of OOM killer. >> Above code's intention is to prevent shortage of ememgency memory pool for avoding >> deadlock. If we already killed any task and the task are in the middle of exiting, >> OOM killer will wait for him to be exited. But the problem in here is that >> killed task might wait any mutex which are held to another task which are >> stuck for the memory allocation and can't use emergency memory pool. :( > > Yeah, there's always a problem if an oom killed process cannot exit > because it's waiting for some other eligible process. This doesn't > normally happen for anything sharing the same mm, though, because we try > to kill anything sharing the same mm when we select a process for oom kill > and if those killed threads happen to call into the oom killer they > silently get TIF_MEMDIE so they may exit as well. This addressed earlier > problems we had with things waiting on mm->mmap_sem in the exit path. > > If the oom killed process cannot exit because it's waiting on another > eligible process that does not share the mm, then we'll potentially > livelock unless you do echo f > /proc/sysrq-trigger manually or turn on > /proc/sys/vm/oom_kill_allocating_task. > >> I think one of solution is that if it takes some seconed(ex, 3 sec) after we already >> kill some task but still looping with above code, we can allow accessing of >> ememgency memory pool for another task. It may happen deadlock due to burn out memory >> pool but otherwise, we still suffer from deadlock. >> > > The problem there is that if the time limit expires (we used 10 seconds > before internally, we don't do it at all anymore) and there are no more > eligible threads that you unnecessarily panic, or open yourself up to a > complete depletion of memory reserves whereas not even the oom killer can > help. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx"> email@xxxxxxxxx </a>