* Mike Galbraith | 2016-01-19 03:29:57 [+0100]:
>> And this is a new piece. So you forbid that tasks leave the CPU if
>> lazy_count > 0. Let me look closed why this is happening and if this is
>> v4.1 … v4.4 or not.
>
>We should probably just add the lazy bits to preemptible().
Subject: preempt-lazy: Add the lazy-preemption check to preempt_schedule()
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>
---
kernel/sched/core.c | 36 ++++++++++++++++++++++++++++--------
1 file changed, 28 insertions(+), 8 deletions(-)
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -3461,6 +3461,30 @@ static void __sched notrace preempt_sche
} 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
@@ -3475,6 +3499,8 @@ asmlinkage __visible void __sched notrac
*/
if (likely(!preemptible()))
return;
+ if (!preemptible_lazy())
+ return;
preempt_schedule_common();
}
@@ -3501,15 +3527,9 @@ asmlinkage __visible void __sched notrac
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_disable_notrace();
/*
--
To unsubscribe from this list: send the line "unsubscribe linux-rt-users" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
