>From the context tracking POV, preempt_schedule_irq() behaves pretty much
like an exception: It can be called anytime and schedule another task.
But currently it doesn't restore the context tracking state of the preempted
code on preempt_schedule_irq() return.
As a result, if preempt_schedule_irq() is called in the tiny frame between
user_enter() and the actual return to userspace, we resume userspace with
the wrong context tracking state.
Fix this by using exception_enter/exit() which are a perfect fit for this
kind of issue.
Signed-off-by: Frederic Weisbecker <fweis...@gmail.com>
Cc: Li Zhong <zh...@linux.vnet.ibm.com>
Cc: Kevin Hilman <khil...@linaro.org>
Cc: Mats Liljegren <mats.liljeg...@enea.com>
Cc: Peter Zijlstra <pet...@infradead.org>
Cc: Ingo Molnar <mi...@kernel.org>
Cc: Steven Rostedt <rost...@goodmis.org>
Cc: Namhyung Kim <namhyung....@lge.com>
Cc: Andrew Morton <a...@linux-foundation.org>
Cc: Thomas Gleixner <t...@linutronix.de>
---
kernel/sched/core.c | 6 +++++-
1 files changed, 5 insertions(+), 1 deletions(-)
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index b7b03cd..db36e11 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -3074,11 +3074,13 @@ EXPORT_SYMBOL(preempt_schedule);
asmlinkage void __sched preempt_schedule_irq(void)
{
struct thread_info *ti = current_thread_info();
+ enum ctx_state prev_state;
/* Catch callers which need to be fixed */
BUG_ON(ti->preempt_count || !irqs_disabled());
- user_exit();
+ prev_state = exception_enter();
+
do {
add_preempt_count(PREEMPT_ACTIVE);
local_irq_enable();
@@ -3092,6 +3094,8 @@ asmlinkage void __sched preempt_schedule_irq(void)
*/
barrier();
} while (need_resched());
+
+ exception_exit(prev_state);
}
#endif /* CONFIG_PREEMPT */
--
1.7.5.4
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