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Date: Sun, 29 Jan 2012 01:14:41 +0100
From: "Rafael J. Wysocki" <rjw@...k.pl>
To: "Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>
Cc: Jiri Slaby <jirislaby@...il.com>, Tejun Heo <tj@...nel.org>,
Jiri Slaby <jslaby@...e.cz>,
LKML <linux-kernel@...r.kernel.org>, Baohua.Song@....com,
"pavel@....cz" <pavel@....cz>,
Linux PM mailing list <linux-pm@...r.kernel.org>
Subject: Re: [linux-pm] PM: cannot hibernate -- BUG at kernel/workqueue.c:3659
On Saturday, January 28, 2012, Srivatsa S. Bhat wrote:
> 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 <srivatsa.bhat@...ux.vnet.ibm.com>
> >>
> >> 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 <rjw@...k.pl>
> > 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 <jslaby@...e.cz>
> > Signed-off-by: Rafael J. Wysocki <rjw@...k.pl>
> > Acked-by: Srivatsa S. Bhat <srivatsa.bhat@...ux.vnet.ibm.com>
>
>
> Cc: stable@...r.kernel.org ?
That's going to show up in the actual commit.
> Other than that, the patch is perfect!
Cool, thanks!
Rafael
> > ---
> > 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:
>
>
> --
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