On Sunday, August 21, 2011, Tejun Heo wrote:
> Hello, Rafafel.
>
> On Sat, Aug 20, 2011 at 06:33:38PM +0200, Rafael J. Wysocki wrote:
> > > ssh://master.kernel.org/pub/scm/linux/kernel/git/tj/misc.git freezer
> >
> > Pulled and stored in the pm-freezer branch in my tree, and merged into
> > the linux-next branch.
>
> Cool.
>
> > > FYI, this patchset will cause a conflict with s390 TIF flag fix patch.
> > > The conflict is trivial and Stephen should be able to handle it
> > > without any problem. Also, I'm planning on doing some further work on
> > > cgroup freezer and then will try to bridge it with job control. If
> > > that plan fans out, I might ask Oleg to pull from the pm tree.
> >
> > I'm not sure if Linus likes it. He generally doesn't want the trees
> > that he pulls from to be entangled this way.
>
> The job control portion has to go through Linus anyway, so let's see
> how that flies.
>
> > > This shouldn't matter too much either way but it *might* be a good idea to
> > > keep this line of patches in a separate branch.
> >
> > I'm going to keep it in the pm-freezer branch anyway (there may be patches
> > on top of it, though)
>
> Yeah, I'm pretty sure it will need some fix too.
Speaking of which, the addition of might_sleep() to try_to_freeze()
causes a badly looking backtrace to appear during reboot on ARM,
so I'd prefer it to go into __refrigerator().
Please tell me what you think of the patch below.
Rafael
---
From: Rafael J. Wysocki <rjw@xxxxxxx>
Subject: PM / Freezer: Move might_sleep() from try_to_freeze()
There are some code paths that call try_to_freeze() from interrupt
context, but doing so they know that the current process cannot
possible be freezing (e.g. during reboot on ARM). However, the
recently added might_sleep() annotation in try_to_freeze()
triggers in those cases, making it look like there were bugs in
those places, which really isn't the case.
Therefore move might_sleep() from try_to_freeze() to
__refrigerator() so that it doesn't produce false positives.
Signed-off-by: Rafael J. Wysocki <rjw@xxxxxxx>
---
include/linux/freezer.h | 1 -
kernel/freezer.c | 2 ++
2 files changed, 2 insertions(+), 1 deletion(-)
Index: linux/include/linux/freezer.h
===================================================================
--- linux.orig/include/linux/freezer.h
+++ linux/include/linux/freezer.h
@@ -41,7 +41,6 @@ extern void thaw_processes(void);
static inline bool try_to_freeze(void)
{
- might_sleep();
if (likely(!freezing(current)))
return false;
return __refrigerator(false);
Index: linux/kernel/freezer.c
===================================================================
--- linux.orig/kernel/freezer.c
+++ linux/kernel/freezer.c
@@ -54,6 +54,8 @@ bool __refrigerator(bool check_kthr_stop
bool was_frozen = false;
long save;
+ might_sleep();
+
/*
* No point in checking freezing() again - the caller already did.
* Proceed to enter FROZEN.
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