From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753841Ab2A1PlQ (ORCPT ); Sat, 28 Jan 2012 10:41:16 -0500 Received: from e28smtp02.in.ibm.com ([122.248.162.2]:34409 "EHLO e28smtp02.in.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753437Ab2A1PlP (ORCPT ); Sat, 28 Jan 2012 10:41:15 -0500 Message-ID: <4F241710.9040205@linux.vnet.ibm.com> Date: Sat, 28 Jan 2012 21:11:04 +0530 From: "Srivatsa S. Bhat" User-Agent: Mozilla/5.0 (X11; Linux i686; rv:9.0) Gecko/20111222 Thunderbird/9.0 MIME-Version: 1.0 To: "Rafael J. Wysocki" CC: Jiri Slaby , Tejun Heo , Jiri Slaby , LKML , Baohua.Song@csr.com, "pavel@ucw.cz" , Linux PM mailing list Subject: Re: [linux-pm] PM: cannot hibernate -- BUG at kernel/workqueue.c:3659 References: <4F1EC8D5.5040102@suse.cz> <201201260051.45000.rjw@sisk.pl> <4F2276AE.7010509@linux.vnet.ibm.com> <201201272344.04086.rjw@sisk.pl> In-Reply-To: <201201272344.04086.rjw@sisk.pl> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit x-cbid: 12012815-5816-0000-0000-0000010F45D8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 01/28/2012 04:14 AM, Rafael J. Wysocki wrote: >> Rafael, thanks for the clarification in the other mail. >> >> Acked-by: Srivatsa S. Bhat >> >> I think we need to get this into 3.2-stable as well, as Jiri mentioned. > > Yes, we do. > > Below it goes again with the missing comment in user.c and a changelog. > > Please let me know if there's anything wrong with it, otherwise I'm going > to push it to Linus in a couple of days. > > Thanks, > Rafael > > --- > From: Rafael J. Wysocki > Subject: PM / Hibernate: Fix s2disk regression related to freezing workqueues > > Commit 2aede851ddf08666f68ffc17be446420e9d2a056 > > PM / Hibernate: Freeze kernel threads after preallocating memory > > introduced a mechanism by which kernel threads were frozen after > the preallocation of hibernate image memory to avoid problems with > frozen kernel threads not responding to memory freeing requests. > However, it overlooked the s2disk code path in which the > SNAPSHOT_CREATE_IMAGE ioctl was run directly after SNAPSHOT_FREE, > which caused freeze_workqueues_begin() to BUG(), because it saw > that worqueues had been already frozen. > > Although in principle this issue might be addressed by removing > the relevant BUG_ON() from freeze_workqueues_begin(), that would > reintroduce the very problem that commit 2aede851ddf08666f68ffc17be4 > attempted to avoid into that particular code path. For this reason, > to fix the issue at hand, introduce thaw_kernel_threads() and make > the SNAPSHOT_FREE ioctl execute it. > > Special thanks to Srivatsa S. Bhat for detailed analysis of the > problem. > > Reported-and-tested-by: Jiri Slaby > Signed-off-by: Rafael J. Wysocki > Acked-by: Srivatsa S. Bhat Cc: stable@vger.kernel.org ? Other than that, the patch is perfect! Regards, Srivatsa S. Bhat > --- > include/linux/freezer.h | 2 ++ > kernel/power/process.c | 19 +++++++++++++++++++ > kernel/power/user.c | 9 +++++++++ > 3 files changed, 30 insertions(+) > > Index: linux/include/linux/freezer.h > =================================================================== > --- linux.orig/include/linux/freezer.h > +++ linux/include/linux/freezer.h > @@ -39,6 +39,7 @@ extern bool __refrigerator(bool check_kt > extern int freeze_processes(void); > extern int freeze_kernel_threads(void); > extern void thaw_processes(void); > +extern void thaw_kernel_threads(void); > > static inline bool try_to_freeze(void) > { > @@ -174,6 +175,7 @@ static inline bool __refrigerator(bool c > static inline int freeze_processes(void) { return -ENOSYS; } > static inline int freeze_kernel_threads(void) { return -ENOSYS; } > static inline void thaw_processes(void) {} > +static inline void thaw_kernel_threads(void) {} > > static inline bool try_to_freeze(void) { return false; } > > Index: linux/kernel/power/process.c > =================================================================== > --- linux.orig/kernel/power/process.c > +++ linux/kernel/power/process.c > @@ -188,3 +188,22 @@ void thaw_processes(void) > printk("done.\n"); > } > > +void thaw_kernel_threads(void) > +{ > + struct task_struct *g, *p; > + > + pm_nosig_freezing = false; > + printk("Restarting kernel threads ... "); > + > + thaw_workqueues(); > + > + read_lock(&tasklist_lock); > + do_each_thread(g, p) { > + if (p->flags & (PF_KTHREAD | PF_WQ_WORKER)) > + __thaw_task(p); > + } while_each_thread(g, p); > + read_unlock(&tasklist_lock); > + > + schedule(); > + printk("done.\n"); > +} > Index: linux/kernel/power/user.c > =================================================================== > --- linux.orig/kernel/power/user.c > +++ linux/kernel/power/user.c > @@ -274,6 +274,15 @@ static long snapshot_ioctl(struct file * > swsusp_free(); > memset(&data->handle, 0, sizeof(struct snapshot_handle)); > data->ready = 0; > + /* > + * It is necessary to thaw kernel threads here, because > + * SNAPSHOT_CREATE_IMAGE may be invoked directly after > + * SNAPSHOT_FREE. In that case, if kernel threads were not > + * thawed, the preallocation of memory carried out by > + * hibernation_snapshot() might run into problems (i.e. it > + * might fail or even deadlock). > + */ > + thaw_kernel_threads(); > break; > > case SNAPSHOT_PREF_IMAGE_SIZE: