Re: PANIC in check_process_timers() running 2.6.11-rc2-mm1

[Alexander Nyberg <alexn@dsv.su.se>]

> Hi Roland
> 
> Just got this running LTP-20050107 on 2.6.11-rc2-mm1, haven't looked
> further yet. Box is i386 UP with preempt, I'm putting dmesg at the 
> bottom of mail.


It's possible that the last refcount of signal->live is dropped in
do_exit and we're interrupted by the timer leaving nthreads to 0.
Takes a few tries to hit but not impossible, this fixes it for me.


Signed-off-by: Alexander Nyberg <alexn@dsv.su.se>

Index: linux-2.6.10/kernel/posix-cpu-timers.c
===================================================================
--- linux-2.6.10.orig/kernel/posix-cpu-timers.c	2005-01-25 17:40:22.000000000 +0100
+++ linux-2.6.10/kernel/posix-cpu-timers.c	2005-01-25 17:43:15.000000000 +0100
@@ -1132,6 +1132,13 @@
 		unsigned long long sched_left, sched;
 		const unsigned int nthreads = atomic_read(&sig->live);
 
+		/*
+		 * We interrupted do_exit and the refcount has dropped,
+		 * leave the task to exit
+		 */
+		if (nthreads == 0)
+			return;
+
 		prof_left = cputime_sub(prof_expires,
 					cputime_add(utime, stime)) / nthreads;
 		virt_left = cputime_sub(virt_expires, utime) / nthreads;