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SubjectRe: [PATCH 1/3] PM suspend/hibernate: Call notifier after freezing processes
Date
On Thursday 09 April 2015 02:28:41 Rafael J. Wysocki wrote:
> On Sunday, April 05, 2015 07:20:17 PM Pali Rohár wrote:
> > To prevent race conditions on userspace processes with I/O
> > some taks must be called after processes are freezed. This
> > patch adds new events which are delivered by
> > pm_notifier_call_chain() after freezing processes when
> > doing suspend or hibernate action.
> >
> > Signed-off-by: Pali Rohár <pali.rohar@gmail.com>
>
> Please don't add more notifiers. Just call whatever you need
> directly from where you need to call that.
>
> If that is device-related, try to use device PM
> suspend/hibernate callbacks instead.
>

Hi! It is not possible to use any exiting pm notifiers! This is
reason why I added new ones. As I wrote wiping dm crypt keys must
be done *after* userspace processes are freezed to prevent race
conditions...

> > ---
> >
> > include/linux/suspend.h | 2 ++
> > kernel/power/hibernate.c | 2 ++
> > kernel/power/suspend.c | 4 +++-
> > 3 files changed, 7 insertions(+), 1 deletion(-)
> >
> > diff --git a/include/linux/suspend.h
> > b/include/linux/suspend.h index 5efe743..bc743c8 100644
> > --- a/include/linux/suspend.h
> > +++ b/include/linux/suspend.h
> > @@ -368,6 +368,8 @@ static inline bool
> > hibernation_available(void) { return false; }
> >
> > #define PM_POST_SUSPEND 0x0004 /* Suspend finished */
> > #define PM_RESTORE_PREPARE 0x0005 /* Going to restore a
> > saved image */ #define PM_POST_RESTORE 0x0006 /*
> > Restore
> > failed */
> >
> > +#define PM_HIBERNATION_AFTER_FREEZE 0x0007 /* After
> > hibernation freeze */ +#define
> > PM_SUSPEND_AFTER_FREEZE 0x0008 /* After suspend freeze */
> >
> > extern struct mutex pm_mutex;
> >
> > diff --git a/kernel/power/hibernate.c
> > b/kernel/power/hibernate.c index 2329daa..184f7ee 100644
> > --- a/kernel/power/hibernate.c
> > +++ b/kernel/power/hibernate.c
> > @@ -671,6 +671,8 @@ int hibernate(void)
> >
> > if (error)
> >
> > goto Exit;
> >
> > + pm_notifier_call_chain(PM_HIBERNATION_AFTER_FREEZE);
> > +
> >
> > lock_device_hotplug();
> > /* Allocate memory management structures */
> > error = create_basic_memory_bitmaps();
> >
> > diff --git a/kernel/power/suspend.c b/kernel/power/suspend.c
> > index b7d6b3a..1776938 100644
> > --- a/kernel/power/suspend.c
> > +++ b/kernel/power/suspend.c
> > @@ -268,8 +268,10 @@ static int
> > suspend_prepare(suspend_state_t state)
> >
> > trace_suspend_resume(TPS("freeze_processes"), 0, true);
> > error = suspend_freeze_processes();
> > trace_suspend_resume(TPS("freeze_processes"), 0, false);
> >
> > - if (!error)
> > + if (!error) {
> > + pm_notifier_call_chain(PM_SUSPEND_AFTER_FREEZE);
> >
> > return 0;
> >
> > + }
> >
> > suspend_stats.failed_freeze++;
> > dpm_save_failed_step(SUSPEND_FREEZE);

--
Pali Rohár
pali.rohar@gmail.com
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