Messages in this thread | | | Date | Tue, 2 Dec 2008 16:30:55 -0800 | From | Andrew Morton <> | Subject | Re: [PATCH] IEEE1284: Use del_timer_sync in parport_wait_event |
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On Sun, 30 Nov 2008 21:20:49 +0100 Michael Buesch <mb@bu3sch.de> wrote:
> Use del_timer_sync() instead of del_timer() to make sure > the timer won't be running when we return from parport_wait_event(), > because this would crash due to destruction of timer_list. > > Signed-off-by: Michael Buesch <mb@bu3sch.de> > > --- > > This is completely untested and just based on a code review. > Just think about the following sequence of events: > add_timer. > down_interruptible is interrupted by a signal. > We enter the timer callback handler on another CPU. > del_timer, but the timer callback is still running. > Return from parport_wait_even, which destroys the automatic variable "timer" > while the callback is running on another CPU. >
Yes, I agree.
> =================================================================== > --- linux-2.6.orig/drivers/parport/ieee1284.c 2008-10-24 21:08:12.000000000 +0200 > +++ linux-2.6/drivers/parport/ieee1284.c 2008-11-30 21:09:25.000000000 +0100 > @@ -84,7 +84,7 @@ int parport_wait_event (struct parport * > > add_timer (&timer); > ret = down_interruptible (&port->physport->ieee1284.irq); > - if (!del_timer (&timer) && !ret) > + if (!del_timer_sync (&timer) && !ret) > /* Timed out. */ > ret = 1;
Please fix checkpatch errors when altering code. This function is already a mismash of correct and incorrect styles - we might as well increase the correctness density.
What we really want in this function is down_interruptible_timeout(). afaict we have all the infrastructure in place to implement that, but nobody has typed
static noinline int __sched __down_interruptible_timeout(struct semaphore *sem, long jiffies) { return __down_common(sem, TASK_INTERRUPTIBLE, jiffies); }
and then tested it.
Or convert the whole thing to mutexes and write mutex_lock_interruptible_timeout() :)
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