From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx149.postini.com [74.125.245.149]) by kanga.kvack.org (Postfix) with SMTP id A512A6B0036 for ; Mon, 24 Jun 2013 16:13:57 -0400 (EDT) Date: Mon, 24 Jun 2013 16:13:45 -0400 From: Johannes Weiner Subject: Re: [PATCH for 3.2] memcg: do not trap chargers with full callstack on OOM Message-ID: <20130624201345.GA21822@cmpxchg.org> References: <20130210150310.GA9504@dhcp22.suse.cz> <20130210174619.24F20488@pobox.sk> <20130211112240.GC19922@dhcp22.suse.cz> <20130222092332.4001E4B6@pobox.sk> <20130606160446.GE24115@dhcp22.suse.cz> <20130606181633.BCC3E02E@pobox.sk> <20130607131157.GF8117@dhcp22.suse.cz> <20130617122134.2E072BA8@pobox.sk> <20130619132614.GC16457@dhcp22.suse.cz> <20130622220958.D10567A4@pobox.sk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20130622220958.D10567A4@pobox.sk> Sender: owner-linux-mm@kvack.org List-ID: To: azurIt Cc: Michal Hocko , linux-kernel@vger.kernel.org, linux-mm@kvack.org, cgroups mailinglist , KAMEZAWA Hiroyuki Hi guys, On Sat, Jun 22, 2013 at 10:09:58PM +0200, azurIt wrote: > >> But i'm sure of one thing - when problem occurs, nothing is able to > >> access hard drives (every process which tries it is freezed until > >> problem is resolved or server is rebooted). > > > >I would be really interesting to see what those tasks are blocked on. > > I'm trying to get it, stay tuned :) > > Today i noticed one bug, not 100% sure it is related to 'your' patch > but i didn't seen this before. I noticed that i have lots of cgroups > which cannot be removed - if i do 'rmdir ', it > just hangs and never complete. Even more, it's not possible to > access the whole cgroup filesystem until i kill that rmdir > (anything, which tries it, just hangs). All unremoveable cgroups has > this in 'memory.oom_control': oom_kill_disable 0 under_oom 1 Somebody acquires the OOM wait reference to the memcg and marks it under oom but then does not call into mem_cgroup_oom_synchronize() to clean up. That's why under_oom is set and the rmdir waits for outstanding references. > And, yes, 'tasks' file is empty. It's not a kernel thread that does it because all kernel-context handle_mm_fault() are annotated properly, which means the task must be userspace and, since tasks is empty, have exited before synchronizing. Can you try with the following patch on top? diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c index 5db0490..9a0b152 100644 --- a/arch/x86/mm/fault.c +++ b/arch/x86/mm/fault.c @@ -846,17 +846,6 @@ static noinline int mm_fault_error(struct pt_regs *regs, unsigned long error_code, unsigned long address, unsigned int fault) { - /* - * Pagefault was interrupted by SIGKILL. We have no reason to - * continue pagefault. - */ - if (fatal_signal_pending(current)) { - if (!(fault & VM_FAULT_RETRY)) - up_read(¤t->mm->mmap_sem); - if (!(error_code & PF_USER)) - no_context(regs, error_code, address); - return 1; - } if (!(fault & VM_FAULT_ERROR)) return 0; -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org