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authorKirill Korotaev <dev@sw.ru>2006-06-27 02:54:32 -0700
committerLinus Torvalds <torvalds@g5.osdl.org>2006-06-27 17:32:44 -0700
commitefc30814a88bdbe2bfe4ac94de2eb089ad80bee3 (patch)
tree1134d7ccda13c09cf426af0524c13633292eac5b /kernel
parentcc94abfcbc9fed0048365ce1fb8dc81353408bf8 (diff)
[PATCH] sched: CPU hotplug race vs. set_cpus_allowed()
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 <dev@openvz.org> Acked-By: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/sched.c18
1 files changed, 14 insertions, 4 deletions
diff --git a/kernel/sched.c b/kernel/sched.c
index 235c421631d..678335a8b39 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -4412,13 +4412,16 @@ 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.
+ *
+ * Returns non-zero if task was successfully migrated.
*/
-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 ret = 0;
if (unlikely(cpu_is_offline(dest_cpu)))
- return;
+ return ret;
rq_src = cpu_rq(src_cpu);
rq_dest = cpu_rq(dest_cpu);
@@ -4446,9 +4449,10 @@ static void __migrate_task(struct task_struct *p, int src_cpu, int dest_cpu)
if (TASK_PREEMPTS_CURR(p, rq_dest))
resched_task(rq_dest->curr);
}
-
+ ret = 1;
out:
double_rq_unlock(rq_src, rq_dest);
+ return ret;
}
/*
@@ -4518,9 +4522,12 @@ wait_to_die:
/* 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)
{
+ runqueue_t *rq;
+ unsigned long flags;
int dest_cpu;
cpumask_t mask;
+restart:
/* On same node? */
mask = node_to_cpumask(cpu_to_node(dead_cpu));
cpus_and(mask, mask, tsk->cpus_allowed);
@@ -4532,8 +4539,10 @@ static void move_task_off_dead_cpu(int dead_cpu, struct task_struct *tsk)
/* 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
@@ -4545,7 +4554,8 @@ static void move_task_off_dead_cpu(int dead_cpu, struct task_struct *tsk)
"longer affine to cpu%d\n",
tsk->pid, tsk->comm, dead_cpu);
}
- __migrate_task(tsk, dead_cpu, dest_cpu);
+ if (!__migrate_task(tsk, dead_cpu, dest_cpu))
+ goto restart;
}
/*