Re: [Bug 10030] Suspend doesn't work when SD card is inserted

Rafael J. Wysocki
2008-02-25T11:43:18Z

On Monday, 25 of February 2008, Alan Stern wrote:
> On Sun, 24 Feb 2008, Rafael J. Wysocki wrote:
>
> > > Very subtly wrong ;-).
> > >
> > > imagine suspending_task == 0xabcdef01. Now task "R" with current ==
> > > 0xabcd0000 reads suspending_task while the other cpu is writing to it,
> > > and sees 0xabcd0000 (0xef01 was not yet written) -- and mistakenly
> > > believes that "R" == suspending_task.
> > >
> > > I agree it is very unlikely, and it will not happen on i386. But what
> > > about just using atomic_t suspending_task, and store current->pid into
> > > it?
> >
> > I'd rather use a lock, frankly. For example, we can require the readers to
> > take pm_sleep_rwsem for reading in order to access that.
>
> That certainly won't work. Imagine what would happen when the reader
> _was_ the suspending task.

Yeah, I've already realized it was a stupid idea. :-)

> But if you really twist my arm, I'll go along with Pavel's suggestion.

So can you do that, pretty please?

Thanks,
Rafael