4.1.15-rt18-rc1 stable review patch.
If anyone has any objections, please let me know.
------------------
From: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
Probably in the rebase onto v4.1 this check got moved into less commonly used
preempt_schedule_notrace(). This patch ensures that both functions use it.
Reported-by: Mike Galbraith <umgwanakikbuti@xxxxxxxxx>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
Signed-off-by: Steven Rostedt <rostedt@xxxxxxxxxxx>
---
kernel/sched/core.c | 36 ++++++++++++++++++++++++++++--------
1 file changed, 28 insertions(+), 8 deletions(-)
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index d21091f2fd1f..5cbfb0548574 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -3116,6 +3116,30 @@ static void __sched notrace preempt_schedule_common(void)
} while (need_resched());
}
+#ifdef CONFIG_PREEMPT_LAZY
+/*
+ * If TIF_NEED_RESCHED is then we allow to be scheduled away since this is
+ * set by a RT task. Oterwise we try to avoid beeing scheduled out as long as
+ * preempt_lazy_count counter >0.
+ */
+static int preemptible_lazy(void)
+{
+ if (test_thread_flag(TIF_NEED_RESCHED))
+ return 1;
+ if (current_thread_info()->preempt_lazy_count)
+ return 0;
+ return 1;
+}
+
+#else
+
+static int preemptible_lazy(void)
+{
+ return 1;
+}
+
+#endif
+
#ifdef CONFIG_PREEMPT
/*
* this is the entry point to schedule() from in-kernel preemption
@@ -3130,6 +3154,8 @@ asmlinkage __visible void __sched notrace preempt_schedule(void)
*/
if (likely(!preemptible()))
return;
+ if (!preemptible_lazy())
+ return;
preempt_schedule_common();
}
@@ -3157,15 +3183,9 @@ asmlinkage __visible void __sched notrace preempt_schedule_context(void)
if (likely(!preemptible()))
return;
-
-#ifdef CONFIG_PREEMPT_LAZY
- /*
- * Check for lazy preemption
- */
- if (current_thread_info()->preempt_lazy_count &&
- !test_thread_flag(TIF_NEED_RESCHED))
+ if (!preemptible_lazy())
return;
-#endif
+
do {
__preempt_count_add(PREEMPT_ACTIVE);
/*
--
2.7.0
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