Date:	Sun, 25 Sep 2011 12:38:47 +0200
From:	Christoph <cr2005@...lub.de>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
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)

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.


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.


chris



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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