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Message-Id: <201109251532.20025.rjw@sisk.pl>
Date: Sun, 25 Sep 2011 15:32:19 +0200
From: "Rafael J. Wysocki" <rjw@...k.pl>
To: Christoph <cr2005@...lub.de>
Cc: Dave Chinner <david@...morbit.com>,
Linux PM mailing list <linux-pm@...ts.linux-foundation.org>,
Pavel Machek <pavel@....cz>,
Nigel Cunningham <nigel@...onice.net>,
Christoph Hellwig <hch@...radead.org>, xfs@....sgi.com,
LKML <linux-kernel@...r.kernel.org>, linux-ext4@...r.kernel.org,
"Theodore Ts'o" <tytso@....edu>, linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH] PM / Freezer: Freeze filesystems while freezing processes (v2)
On Sunday, September 25, 2011, Christoph wrote:
> test results of the patch below:
>
> 1. real machine
>
> suspends fine but on wakeup, after loading image: hard reset.
> nvidia gpu => disabled compitz => wakeup worked two times.
Hmm, so there's a separate bug related to NVidia I guess.
> 2. virtualbox / stress test / xfs and ext4
>
> on 3rd resume, it booted up "normal" like this:
>
> [ 3.351813] Freeing unused kernel memory: 568k freed
> [ 3.460973] Freeing unused kernel memory: 284k freed
>
> [ 17.328356] PM: Preparing processes for restore.
>
> [ 17.328357] Freezing user space processes ...
> [ 37.345414] Freezing of tasks failed after 20.01 seconds (1 tasks
> refusing to freeze, wq_busy=0):
> [ 37.475244] ffff88001f06fd68 0000000000000086 0000000000000000
> 0000000000000000
> [ 37.526163] ffff88001f06e010 ffff88001f4c4410 0000000000012ec0
> ffff88001f06ffd8
> [ 37.580110] ffff88001f06ffd8 0000000000012ec0 ffffffff8160d020
> ffff88001f4c4410
> [ 37.626167] Call Trace:
> [ 37.626769] [<ffffffff81049944>] schedule+0x55/0x57
> [ 37.674925] [<ffffffff81360dbe>] __mutex_lock_common+0x117/0x178
> [ 37.792559] [<ffffffff81113ef2>] ? user_path_at+0x61/0x90
> [ 37.888501] [<ffffffff81360e35>] __mutex_lock_slowpath+0x16/0x18
> [ 37.986966] [<ffffffff81360efb>] mutex_lock+0x1e/0x32
> [ 38.086931] [<ffffffffa00a4d43>] show_manufacturer+0x23/0x51 [usbcore]
> [ 38.212500] [<ffffffff8125cd44>] dev_attr_show+0x22/0x49
> [ 38.282319] [<ffffffff810c6f8c>] ? __get_free_pages+0x9/0x38
> [ 38.397449] [<ffffffff8115febb>] sysfs_read_file+0xa9/0x12b
> [ 38.491607] [<ffffffff81107ff6>] vfs_read+0xa6/0x102
> [ 38.541994] [<ffffffff81105ebf>] ? do_sys_open+0xee/0x100
> [ 38.564907] [<ffffffff8110810b>] sys_read+0x45/0x6c
> [ 38.578397] [<ffffffff81368412>] system_call_fastpath+0x16/0x1b
> [ 38.590083]
> [ 38.598046] Restarting tasks ... done.
> [ 38.660448] XFS (sda3): Mounting Filesystem
>
> restarted the test runs, increased delay between awake and sleep from 20
> to 25 sec:
>
> 36 time successful hibernate+resume so far.
OK, cool. Thanks for testing!
Rafael
> On 25.09.2011 00:56, Rafael J. Wysocki wrote:
> > On Sunday, August 07, 2011, Dave Chinner wrote:
> >> On Sat, Aug 06, 2011 at 11:17:18PM +0200, Rafael J. Wysocki wrote:
> >>> From: Rafael J. Wysocki <rjw@...k.pl>
> >>>
> >>> Freeze all filesystems during the freezing of tasks by calling
> >>> freeze_bdev() for each of them and thaw them during the thawing
> >>> of tasks with the help of thaw_bdev().
> >>>
> >>> This is needed by hibernation, because some filesystems (e.g. XFS)
> >>> deadlock with the preallocation of memory used by it if the memory
> >>> pressure caused by it is too heavy.
> >>>
> >>> The additional benefit of this change is that, if something goes
> >>> wrong after filesystems have been frozen, they will stay in a
> >>> consistent state and journal replays won't be necessary (e.g. after
> >>> a failing suspend or resume). In particular, this should help to
> >>> solve a long-standing issue that in some cases during resume from
> >>> hibernation the boot loader causes the journal to be replied for the
> >>> filesystem containing the kernel image and initrd causing it to
> >>> become inconsistent with the information stored in the hibernation
> >>> image.
> >>>
> >>> This change is based on earlier work by Nigel Cunningham.
> >>>
> >>> Signed-off-by: Rafael J. Wysocki <rjw@...k.pl>
> >>> ---
> >
> > Below is an alternative fix, the changelog pretty much explains the idea.
> >
> > I've tested it on Toshiba Portege R500, but I don't have an XFS partition
> > to verify that it really helps, so I'd appreciate it if someone able to
> > reproduce the original issue could test it and report back.
> >
> > Thanks,
> > Rafael
> >
> > ---
> > From: Rafael J. Wysocki <rjw@...k.pl>
> > Subject: PM / Hibernate: Freeze kernel threads after preallocating memory
> >
> > There is a problem with the current ordering of hibernate code which
> > leads to deadlocks in some filesystems' memory shrinkers. Namely,
> > some filesystems use freezable kernel threads that are inactive when
> > the hibernate memory preallocation is carried out. Those same
> > filesystems use memory shrinkers that may be triggered by the
> > hibernate memory preallocation. If those memory shrinkers wait for
> > the frozen kernel threads, the hibernate process deadlocks (this
> > happens with XFS, for one example).
> >
> > Apparently, it is not technically viable to redesign the filesystems
> > in question to avoid the situation described above, so the only
> > possible solution of this issue is to defer the freezing of kernel
> > threads until the hibernate memory preallocation is done, which is
> > implemented by this change.
> >
> > Signed-off-by: Rafael J. Wysocki <rjw@...k.pl>
> > ---
> > include/linux/freezer.h | 4 +++-
> > kernel/power/hibernate.c | 12 ++++++++----
> > kernel/power/power.h | 3 ++-
> > kernel/power/process.c | 30 ++++++++++++++++++++----------
> > 4 files changed, 33 insertions(+), 16 deletions(-)
> >
> > Index: linux/kernel/power/process.c
> > ===================================================================
> > --- linux.orig/kernel/power/process.c
> > +++ linux/kernel/power/process.c
> > @@ -135,7 +135,7 @@ static int try_to_freeze_tasks(bool sig_
> > }
> >
> > /**
> > - * freeze_processes - tell processes to enter the refrigerator
> > + * freeze_processes - Signal user space processes to enter the refrigerator.
> > */
> > int freeze_processes(void)
> > {
> > @@ -143,20 +143,30 @@ int freeze_processes(void)
> >
> > printk("Freezing user space processes ... ");
> > error = try_to_freeze_tasks(true);
> > - if (error)
> > - goto Exit;
> > - printk("done.\n");
> > + if (!error) {
> > + printk("done.");
> > + oom_killer_disable();
> > + }
> > + printk("\n");
> > + BUG_ON(in_atomic());
> > +
> > + return error;
> > +}
> > +
> > +/**
> > + * freeze_kernel_threads - Make freezable kernel threads go to the refrigerator.
> > + */
> > +int freeze_kernel_threads(void)
> > +{
> > + int error;
> >
> > printk("Freezing remaining freezable tasks ... ");
> > error = try_to_freeze_tasks(false);
> > - if (error)
> > - goto Exit;
> > - printk("done.");
> > + if (!error)
> > + printk("done.");
> >
> > - oom_killer_disable();
> > - Exit:
> > - BUG_ON(in_atomic());
> > printk("\n");
> > + BUG_ON(in_atomic());
> >
> > return error;
> > }
> > Index: linux/include/linux/freezer.h
> > ===================================================================
> > --- linux.orig/include/linux/freezer.h
> > +++ linux/include/linux/freezer.h
> > @@ -49,6 +49,7 @@ extern int thaw_process(struct task_stru
> >
> > extern void refrigerator(void);
> > extern int freeze_processes(void);
> > +extern int freeze_kernel_threads(void);
> > extern void thaw_processes(void);
> >
> > static inline int try_to_freeze(void)
> > @@ -171,7 +172,8 @@ static inline void clear_freeze_flag(str
> > static inline int thaw_process(struct task_struct *p) { return 1; }
> >
> > static inline void refrigerator(void) {}
> > -static inline int freeze_processes(void) { BUG(); return 0; }
> > +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 int try_to_freeze(void) { return 0; }
> > Index: linux/kernel/power/power.h
> > ===================================================================
> > --- linux.orig/kernel/power/power.h
> > +++ linux/kernel/power/power.h
> > @@ -228,7 +228,8 @@ extern int pm_test_level;
> > #ifdef CONFIG_SUSPEND_FREEZER
> > static inline int suspend_freeze_processes(void)
> > {
> > - return freeze_processes();
> > + int error = freeze_processes();
> > + return error ? : freeze_kernel_threads();
> > }
> >
> > static inline void suspend_thaw_processes(void)
> > Index: linux/kernel/power/hibernate.c
> > ===================================================================
> > --- linux.orig/kernel/power/hibernate.c
> > +++ linux/kernel/power/hibernate.c
> > @@ -334,13 +334,17 @@ int hibernation_snapshot(int platform_mo
> > if (error)
> > goto Close;
> >
> > - error = dpm_prepare(PMSG_FREEZE);
> > - if (error)
> > - goto Complete_devices;
> > -
> > /* Preallocate image memory before shutting down devices. */
> > error = hibernate_preallocate_memory();
> > if (error)
> > + goto Close;
> > +
> > + error = freeze_kernel_threads();
> > + if (error)
> > + goto Close;
> > +
> > + error = dpm_prepare(PMSG_FREEZE);
> > + if (error)
> > goto Complete_devices;
> >
> > suspend_console();
>
--
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