Looks like there is a race between set_cpus_allowed()
and move_task_off_dead_cpu().
__migrate_task() doesn't report any err code, so
task can be left on its runqueue if its cpus_allowed mask
changed so that dest_cpu is not longer a possible target.
Also, chaning cpus_allowed mask requires rq->lock being held.
Signed-Off-By: Kirill Korotaev <[email protected]>
Kirill
P.S. against 2.6.17-mm1
--- linux-2.6.17-mm1s.orig/kernel/sched.c 2006-06-21 18:53:17.000000000 +0400
+++ linux-2.6.17-mm1.dev/kernel/sched.c 2006-06-23 12:09:16.000000000 +0400
@@ -4858,12 +4858,13 @@ EXPORT_SYMBOL_GPL(set_cpus_allowed);
* So we race with normal scheduler movements, but that's OK, as long
* as the task is no longer on this CPU.
*/
-static void __migrate_task(struct task_struct *p, int src_cpu, int dest_cpu)
+static int __migrate_task(struct task_struct *p, int src_cpu, int dest_cpu)
{
runqueue_t *rq_dest, *rq_src;
+ int res = 0;
if (unlikely(cpu_is_offline(dest_cpu)))
- return;
+ return 0;
rq_src = cpu_rq(src_cpu);
rq_dest = cpu_rq(dest_cpu);
@@ -4891,9 +4892,10 @@ static void __migrate_task(struct task_s
if (TASK_PREEMPTS_CURR(p, rq_dest))
resched_task(rq_dest->curr);
}
-
+ res = 1;
out:
double_rq_unlock(rq_src, rq_dest);
+ return res;
}
/*
@@ -4964,10 +4966,13 @@ int sigstop_on_cpu_lost;
/* Figure out where task on dead CPU should go, use force if neccessary. */
static void move_task_off_dead_cpu(int dead_cpu, struct task_struct *tsk)
{
- int dest_cpu;
+ runqueue_t *rq;
+ unsigned long flags;
+ int dest_cpu, res;
cpumask_t mask;
int force = 0;
+restart:
/* On same node? */
mask = node_to_cpumask(cpu_to_node(dead_cpu));
cpus_and(mask, mask, tsk->cpus_allowed);
@@ -4979,8 +4984,10 @@ static void move_task_off_dead_cpu(int d
/* No more Mr. Nice Guy. */
if (dest_cpu == NR_CPUS) {
+ rq = task_rq_lock(tsk, &flags);
cpus_setall(tsk->cpus_allowed);
dest_cpu = any_online_cpu(tsk->cpus_allowed);
+ task_rq_unlock(rq, &flags);
/*
* Don't tell them about moving exiting tasks or
@@ -5000,7 +5007,9 @@ static void move_task_off_dead_cpu(int d
if (tsk->mm && sigstop_on_cpu_lost)
force = 1;
}
- __migrate_task(tsk, dead_cpu, dest_cpu);
+ res = __migrate_task(tsk, dead_cpu, dest_cpu);
+ if (!res)
+ goto restart;
if (force)
force_sig_specific(SIGSTOP, tsk);
[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]
