From mboxrd@z Thu Jan 1 00:00:00 1970 From: Darren Hart Subject: Re: 3.11-rc regression bisected: s2disk does not work (was Re: [PATCH v3 13/16] futex: use freezable blocking call) Date: Tue, 23 Jul 2013 11:24:35 -0700 Message-ID: <1374603875.3436.149.camel@dvhart-mobl1.amr.corp.intel.com> References: <1367884221-20462-1-git-send-email-ccross@android.com> <1367884221-20462-14-git-send-email-ccross@android.com> <20130723010250.5a3465ec@xenia.leun.net> <20130723200854.2046296b@xenia.leun.net> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Cc: Colin Cross , lkml , Pavel Machek , "Rafael J. Wysocki" , Peter Zijlstra , Ingo Molnar , Andrew Morton , Mandeep Singh Baines , Oleg Nesterov , linux-nfs , Linux PM list , netdev , Linus Torvalds , Tejun Heo , Thomas Gleixner , Randy Dunlap , Al Viro To: Michael Leun Return-path: In-Reply-To: <20130723200854.2046296b@xenia.leun.net> Sender: linux-pm-owner@vger.kernel.org List-Id: netdev.vger.kernel.org On Tue, 2013-07-23 at 20:08 +0200, Michael Leun wrote: > On Mon, 22 Jul 2013 16:55:58 -0700 > Colin Cross wrote: > > > On Mon, Jul 22, 2013 at 4:02 PM, Michael Leun > > wrote: > > > On Mon, 6 May 2013 16:50:18 -0700 > > > Colin Cross wrote: > > > > > >> Avoid waking up every thread sleeping in a futex_wait call during > > > [...] > > > > > > With 3.11-rc s2disk from suspend-utils stopped working: Frozen at > > > displaying 0% of saving image to disk. > > > > > > echo "1" >/sys/power/state still works. > > > > > > Bisecting yielded 88c8004fd3a5fdd2378069de86b90b21110d33a4, > > > reverting that from 3.11-rc2 makes s2disk working again. > > > > > > > I think the expanded use of the freezable_* helpers is exposing an > > existing bug in hibernation. The SNAPSHOT_FREEZE ioctl calls > > freeze_processes(), which sets the global system_freezing_cnt and > > pm_freezing. try_to_freeze_tasks then sends every process except > > current a signal which causes them all to end up in the refrigerator. > > The current task then returns back to userspace and continues its work > > to suspend to disk. If that task ever hits a call to try_to_freeze() > > in the kernel, it will see system_freezing_cnt and pm_freezing=true > > and freeze, and suspend to disk will hang forever. It could hit > > try_to_freeze() because of a signal delivered to the task, or from > > calling any syscall that uses a freezable_* helper like the one I > > added to sys_futex. > > > > I think the right solution is to add a flag to the freezing task that > > marks it unfreezable. I think PF_NOFREEZE would work, although it is > > normally used on kernel threads, can you see if the attached patch > > helps? > > That patch helps. > > BTW, the only machine I can reproduce this bug with is an i7-3630QM > notebook. Cannot reproduce on an Core Duo U1400 and cannot reproduce on > an i7 M 620. > > Are the sysreq backtraces still wanted? If so, any tip, how I could get > them saved? Typically by setting up a serial console or a netconsole and saving the log from the attached terminal emulator (such as screen or minicom). Is this what you are asking? -- Darren Hart Intel Open Source Technology Center Yocto Project - Linux Kernel