sched/x86: Do not clear PREEMPT_NEED_RESCHED on preempt count reset

The per-cpu preempt count of x86 contains two values, the actual preempt
count and the inverted PREEMPT_NEED_RESCHED bit. If a corrupted preempt
count is detected the preempt_count_set() function is used to reset the
preempt count.

In case the inverted PREEMPT_NEED_RESCHED bit is zero at the time of the
reset, the preemption indication is lost. Use raw_cpu_cmpxchg_4() to reset
only the count part and leave the PREEMPT_NEED_RESCHED bit as it is.

This improves the kernel's behavior when it runs into preempt count leaks
and tries to fix them up.

Signed-off-by: Martin Schwidefsky <[email protected]>
Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Ingo Molnar <[email protected]>

0 files changed, 0 insertions, 0 deletions