On Fri, 20 Jul 2007, Oleg Nesterov wrote:
On 07/18, Jeremy Katz wrote:
On Wed, 18 Jul 2007, Oleg Nesterov wrote:
Jeremy, I agree with Thomas that your patch should not be right, but it
does make a difference. Perhaps this is just the timing, but who knows.
Could you add some printk's to be sure that lock_timer() actually fails
while it never should?
Agreed.
Unfortunately, adding any significant output appears to alter the
situation to the point where the issue either does not occur, or takes
significantly longer to surface.
No, no, I didn't mean any significant output. You changed itimer_delete()
> - spin_lock_irqsave(&timer->it_lock, flags);
> + /* timer already deleted? */
> + if (lock_timer(timer->it_id, &flags) == NULL)
> + return;
This change should not help, lock_timer() should always succeed here.
But since it makes a difference, we can make something like
if (lock_timer(timer->it_id, &flags) == NULL) {
printk("Impossible! but it happened.\n");
return;
}
The same for posix_timer_fn().
Ahh, of course. I did try that at some point, and remember seeing at
least the occasional failure. This time, taking the spinlock and then
checking for a valid timer ID, I did not see the locking fail. I did see
the attempt to use a freed sigqueue, further suggesting my 'fix' merely
altered the timing sufficiently to hide the issue.
I still can't believe we have a double-free problem, this looks imposiible.
Do you see the
"idr_remove called for id=%d which is not allocated.\n"
in syslog?
No. I also added some accounting with atomic counters, and don't see
evidence of a second call to release_posix_timer.
Could you try the patch below? Perhaps we have some wierd problem with
->sigq corruption.
Tried, with apparent effect.
To add to the body of data: Turning off hyperthreading in the hardware
does not resolve the issue. Limiting the system to one CPU does appear to
work.
Jeremy
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [email protected]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
[Index of Archives]
[Kernel Newbies]
[Netfilter]
[Bugtraq]
[Photo]
[Stuff]
[Gimp]
[Yosemite News]
[MIPS Linux]
[ARM Linux]
[Linux Security]
[Linux RAID]
[Video 4 Linux]
[Linux for the blind]
[Linux Resources]
