On Tuesday, July 23, 2013 11:29:57 AM Colin Cross wrote: > On Tue, Jul 23, 2013 at 11:08 AM, Michael Leun > <lkml20130126@xxxxxxxxxxxxxxx> wrote: > > On Mon, 22 Jul 2013 16:55:58 -0700 > > Colin Cross <ccross@xxxxxxxxxxx> wrote: > > > >> On Mon, Jul 22, 2013 at 4:02 PM, Michael Leun > >> <lkml20130126@xxxxxxxxxxxxxxx> wrote: > >> > On Mon, 6 May 2013 16:50:18 -0700 > >> > Colin Cross <ccross@xxxxxxxxxxx> 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? > > > > > > -- > > MfG, > > > > Michael Leun > > > > Any chance that the failing machine has threads=y in the suspend.conf file? > > Rafael, it appears that swsusp's suspend.c spawns new threads after > calling the SNAPSHOT_FREEZE ioctl. The PF_NOFREEZE (or the new flag) > will get copied to those new threads, but nothing will clear the flag. > Should I just assume that the userspace suspend code will kill those > threads before continuing with suspend? Or maybe add a WARN_ON in the > kernel if any threads besides current have the new flag set when the > suspend ops that assume all of userspace is frozen are called? Those threads should be killed by user space. They are only spawned for image saving/compression/encryption and should be waited for after that. Thanks, Rafael -- I speak only for myself. Rafael J. Wysocki, Intel Open Source Technology Center. -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
