L-Team Captain,
In set_cpus_allowed(), we hold the preempt_disable() over a
wait_for_completition() so it triggers the atomicity debugging.
There is (was) a kernel preemption race here which the preemption
disable is fixing. I do not understand it; if this uncovers it there
should be some light shed on the subject.
Anyhow, attached patch fixes the atomicity debugging error.
Patch is against current BK. Please, apply.
Robert Love
sched.c | 13 ++++++++-----
1 files changed, 8 insertions(+), 5 deletions(-)
diff -urN linux-bk/kernel/sched.c linux/kernel/sched.c
--- linux-bk/kernel/sched.c 2002-10-09 15:46:43.000000000 -0400
+++ linux/kernel/sched.c 2002-10-09 18:52:06.000000000 -0400
@@ -1953,7 +1953,6 @@
BUG();
#endif
- preempt_disable();
rq = task_rq_lock(p, &flags);
p->cpus_allowed = new_mask;
/*
@@ -1962,7 +1961,7 @@
*/
if (new_mask & (1UL << task_cpu(p))) {
task_rq_unlock(rq, &flags);
- goto out;
+ return;
}
/*
* If the task is not on a runqueue (and not running), then
@@ -1971,17 +1970,21 @@
if (!p->array && !task_running(rq, p)) {
set_task_cpu(p, __ffs(p->cpus_allowed));
task_rq_unlock(rq, &flags);
- goto out;
+ return;
}
init_completion(&req.done);
req.task = p;
list_add(&req.list, &rq->migration_queue);
+
+ /*
+ * counter the subsequent unlock - we do not want to preempt yet
+ */
+ preempt_disable();
task_rq_unlock(rq, &flags);
wake_up_process(rq->migration_thread);
+ preempt_enable();
wait_for_completion(&req.done);
-out:
- preempt_enable();
}
/*
-
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This archive was generated by hypermail 2b29 : Tue Oct 15 2002 - 22:00:34 EST