Re: preempt-related hangs

[Andrew Morton <akpm@zip.com.au>]

Andrew Morton wrote:
> 
> ..
> Kernel is 2.5.7, dual PIII.  When I enable preempt it
> locks during boot.

OK, this patch fixed it.  I don't know why.


--- linux-2.5.7/kernel/sched.c	Mon Mar 18 13:04:41 2002
+++ 25/kernel/sched.c	Sun Mar 24 18:09:09 2002
@@ -1545,6 +1545,8 @@ void set_cpus_allowed(task_t *p, unsigne
 	migration_req_t req;
 	runqueue_t *rq;
 
+	preempt_disable();
+
 	new_mask &= cpu_online_map;
 	if (!new_mask)
 		BUG();
@@ -1557,7 +1559,7 @@ void set_cpus_allowed(task_t *p, unsigne
 	 */
 	if (new_mask & (1UL << p->thread_info->cpu)) {
 		task_rq_unlock(rq, &flags);
-		return;
+		goto out;
 	}
 
 	init_MUTEX_LOCKED(&req.sem);
@@ -1567,6 +1569,8 @@ void set_cpus_allowed(task_t *p, unsigne
 	wake_up_process(rq->migration_thread);
 
 	down(&req.sem);
+out:
+	preempt_disable();
 }
 
 static volatile unsigned long migration_mask;


-