Re: [PATCH -mm] swsusp: Freeze filesystems during suspend (rev. 2)

Rafael J. Wysocki
2006-11-02T20:55:51Z

On Wednesday, 1 November 2006 22:21, Andrew Morton wrote:
> On Wed, 1 Nov 2006 21:27:17 +0100
> "Rafael J. Wysocki" <rjw@sisk.pl> wrote:
>
> > On Wednesday, 1 November 2006 20:45, Andrew Morton wrote:
> > > On Wed, 1 Nov 2006 18:53:07 +0100
> > > "Rafael J. Wysocki" <rjw@sisk.pl> wrote:
> > >
> > > > +void thaw_processes(void)
> > > > +{
> > > > + printk("Restarting tasks ... ");
> > > > + __thaw_tasks(FREEZER_KERNEL_THREADS);
> > > > + thaw_filesystems();
> > > > + __thaw_tasks(FREEZER_USER_SPACE);
> > > > + schedule();
> > > > + printk("done.\n");
> > > > +}
> > > >
> > > > - read_unlock(&tasklist_lock);
> > > > +void thaw_kernel_threads(void)
> > > > +{
> > > > + printk("Restarting kernel threads ... ");
> > > > + __thaw_tasks(FREEZER_KERNEL_THREADS);
> > > > schedule();
> > > > printk("done.\n");
> > > > }
> > >
> > > what do these random-looking schedule()s do??
> >
> > My understanding is that they allow the thawed tasks to actually exit
> > the refrigerator, because __thaw_tasks() only changes their states.
>
> I'd be surprised if this is doing what we thing it's doing. Calling
> schedule() in state TASK_RUNNING is usually a no-op. It'll only actually
> switch to another task if the scheduler decides that this task has expired
> its timeslice, or another higher-priority task has become runnable, etc.

This actually can happen, it seems, because __thaw_tasks() calls
wake_up_process() for each frozen task which may call resched_task() for
current.