Re: [RFC][PATCH -mm 1/5] PM: Make freeze_processes SMP-safe

Rafael J. Wysocki
2006-11-27T20:02:38Z

On Monday, 27 November 2006 11:50, Pavel Machek wrote:
> Hi!
>
> > > > @@ -61,10 +60,13 @@ static inline void freeze_process(struct
> > > > unsigned long flags;
> > > >
> > > > if (!freezing(p)) {
> > > > - freeze(p);
> > > > - spin_lock_irqsave(&p->sighand->siglock, flags);
> > > > - signal_wake_up(p, 0);
> > > > - spin_unlock_irqrestore(&p->sighand->siglock, flags);
> > > > + rmb();
> > >
> > > If frozen is atomic_t, do we need memory barrier?
> >
> > I think so. For example on x86-64 atomic_read() is just a read.
>
> Sorry for one more change, but
>
>
> /* set thread flags in other task's structures
> * - see asm/thread_info.h for TIF_xxxx flags available
> */
> static inline void set_tsk_thread_flag(struct task_struct *tsk, int
> flag)
> {
> set_ti_thread_flag(task_thread_info(tsk), flag);
> }
>
> ...could we use set_tsk_thread_flag and friends to avoid enlarging
> task struct?

_Of_ _course_. [Heh, I didn't even know something like this existed. ;-)]

Greetings,
Rafael

--
You never change things by fighting the existing reality.
R. Buckminster Fuller