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authorPeter Zijlstra <peterz@infradead.org>2013-11-20 12:22:37 +0100
committerIngo Molnar <mingo@kernel.org>2014-01-13 17:38:55 +0100
commit8cb75e0c4ec9786b81439761eac1d18d4a931af3 (patch)
tree9d13e6c3580a36cd76d1b3a96827795949519409 /kernel
parentc9c8986847d2f4fc474c10ee08afa57e7474096d (diff)
sched/preempt: Fix up missed PREEMPT_NEED_RESCHED folding
With various drivers wanting to inject idle time; we get people calling idle routines outside of the idle loop proper. Therefore we need to be extra careful about not missing TIF_NEED_RESCHED -> PREEMPT_NEED_RESCHED propagations. While looking at this, I also realized there's a small window in the existing idle loop where we can miss TIF_NEED_RESCHED; when it hits right after the tif_need_resched() test at the end of the loop but right before the need_resched() test at the start of the loop. So move preempt_fold_need_resched() out of the loop where we're guaranteed to have TIF_NEED_RESCHED set. Signed-off-by: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/n/tip-x9jgh45oeayzajz2mjt0y7d6@git.kernel.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/cpu/idle.c17
-rw-r--r--kernel/sched/core.c3
2 files changed, 11 insertions, 9 deletions
diff --git a/kernel/cpu/idle.c b/kernel/cpu/idle.c
index 988573a9a387..277f494c2a9a 100644
--- a/kernel/cpu/idle.c
+++ b/kernel/cpu/idle.c
@@ -105,14 +105,17 @@ static void cpu_idle_loop(void)
__current_set_polling();
}
arch_cpu_idle_exit();
- /*
- * We need to test and propagate the TIF_NEED_RESCHED
- * bit here because we might not have send the
- * reschedule IPI to idle tasks.
- */
- if (tif_need_resched())
- set_preempt_need_resched();
}
+
+ /*
+ * Since we fell out of the loop above, we know
+ * TIF_NEED_RESCHED must be set, propagate it into
+ * PREEMPT_NEED_RESCHED.
+ *
+ * This is required because for polling idle loops we will
+ * not have had an IPI to fold the state for us.
+ */
+ preempt_set_need_resched();
tick_nohz_idle_exit();
schedule_preempt_disabled();
}
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 392c6f87906e..0326c06953eb 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -1510,8 +1510,7 @@ void scheduler_ipi(void)
* TIF_NEED_RESCHED remotely (for the first time) will also send
* this IPI.
*/
- if (tif_need_resched())
- set_preempt_need_resched();
+ preempt_fold_need_resched();
if (llist_empty(&this_rq()->wake_list)
&& !tick_nohz_full_cpu(smp_processor_id())