lkml.org 
[lkml]   [2013]   [Mar]   [1]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH 3/5] context_tracking: Restore preempted context state after preempt_schedule_irq()
Date
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 <fweisbec@gmail.com>
Cc: Li Zhong <zhong@linux.vnet.ibm.com>
Cc: Kevin Hilman <khilman@linaro.org>
Cc: Mats Liljegren <mats.liljegren@enea.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Namhyung Kim <namhyung.kim@lge.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Thomas Gleixner <tglx@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


\
 
 \ /
  Last update: 2013-03-01 17:42    [W:1.626 / U:0.020 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site