rt-patches/0359-x86-preempt-lazy-fixup-should_resched.patch

   1 From 87495fd5e4eae1f98aafeb38074489c503a6717f Mon Sep 17 00:00:00 2001
   2 From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
   3 Date: Wed, 14 Sep 2016 19:18:47 +0200
   4 Subject: [PATCH 359/366] x86/preempt-lazy: fixup should_resched()
   5
   6 should_resched() returns true if NEED_RESCHED is set and the
   7 preempt_count is 0 _or_ if NEED_RESCHED_LAZY is set ignoring the preempt
   8 counter. Ignoring the preemp counter is wrong. This patch adds this into
   9 account.
  10 While at it, __preempt_count_dec_and_test() ignores preempt_lazy_count
  11 while checking TIF_NEED_RESCHED_LAZY so we this check, too.
  12
  13 Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
  14 Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
  15 ---
  16  arch/x86/include/asm/preempt.h | 17 +++++++++++++++--
  17  1 file changed, 15 insertions(+), 2 deletions(-)
  18
  19 diff --git a/arch/x86/include/asm/preempt.h b/arch/x86/include/asm/preempt.h
  20 index 5dbd2d0..6f432ad 100644
  21 --- a/arch/x86/include/asm/preempt.h
  22 +++ b/arch/x86/include/asm/preempt.h
  23 @@ -89,6 +89,8 @@ static __always_inline bool __preempt_count_dec_and_test(void)
  24         if (____preempt_count_dec_and_test())
  25                 return true;
  26  #ifdef CONFIG_PREEMPT_LAZY
  27 +       if (current_thread_info()->preempt_lazy_count)
  28 +               return false;
  29         return test_thread_flag(TIF_NEED_RESCHED_LAZY);
  30  #else
  31         return false;
  32 @@ -101,8 +103,19 @@ static __always_inline bool __preempt_count_dec_and_test(void)
  33  static __always_inline bool should_resched(int preempt_offset)
  34  {
  35  #ifdef CONFIG_PREEMPT_LAZY
  36 -       return unlikely(raw_cpu_read_4(__preempt_count) == preempt_offset ||
  37 -                       test_thread_flag(TIF_NEED_RESCHED_LAZY));
  38 +       u32 tmp;
  39 +
  40 +       tmp = raw_cpu_read_4(__preempt_count);
  41 +       if (tmp == preempt_offset)
  42 +               return true;
  43 +
  44 +       /* preempt count == 0 ? */
  45 +       tmp &= ~PREEMPT_NEED_RESCHED;
  46 +       if (tmp)
  47 +               return false;
  48 +       if (current_thread_info()->preempt_lazy_count)
  49 +               return false;
  50 +       return test_thread_flag(TIF_NEED_RESCHED_LAZY);
  51  #else
  52         return unlikely(raw_cpu_read_4(__preempt_count) == preempt_offset);
  53  #endif
  54 --
  55 1.9.1
  56