[PATCH RT 08/10] x86/preempt-lazy: fixup should_resched()

Steven Rostedt
2016-09-22T23:18:40Z

[-- Attachment #1: 0008-x86-preempt-lazy-fixup-should_resched.patch --]
[-- Type: text/plain, Size: 1856 bytes --]

3.18.42-rt45-rc1 stable review patch.
If anyone has any objections, please let me know.

------------------

From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>

should_resched() returns true if NEED_RESCHED is set and the
preempt_count is 0 _or_ if NEED_RESCHED_LAZY is set ignoring the preempt
counter. Ignoring the preemp counter is wrong. This patch adds this into
account.
While at it, __preempt_count_dec_and_test() ignores preempt_lazy_count
while checking TIF_NEED_RESCHED_LAZY so we this check, too.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
arch/x86/include/asm/preempt.h | 16 ++++++++++++++--
1 file changed, 14 insertions(+), 2 deletions(-)

diff --git a/arch/x86/include/asm/preempt.h b/arch/x86/include/asm/preempt.h
index 060d1b4e475d..6806369bddf5 100644
--- a/arch/x86/include/asm/preempt.h
+++ b/arch/x86/include/asm/preempt.h
@@ -95,6 +95,8 @@ static __always_inline bool __preempt_count_dec_and_test(void)
if (____preempt_count_dec_and_test())
return true;
#ifdef CONFIG_PREEMPT_LAZY
+ if (current_thread_info()->preempt_lazy_count)
+ return false;
return test_thread_flag(TIF_NEED_RESCHED_LAZY);
#else
return false;
@@ -107,8 +109,18 @@ static __always_inline bool __preempt_count_dec_and_test(void)
static __always_inline bool should_resched(void)
{
#ifdef CONFIG_PREEMPT_LAZY
- return unlikely(!raw_cpu_read_4(__preempt_count) || \
- test_thread_flag(TIF_NEED_RESCHED_LAZY));
+ u32 tmp;
+
+ if (!raw_cpu_read_4(__preempt_count))
+ return true;
+
+ /* preempt count == 0 ? */
+ tmp &= ~PREEMPT_NEED_RESCHED;
+ if (tmp)
+ return false;
+ if (current_thread_info()->preempt_lazy_count)
+ return false;
+ return test_thread_flag(TIF_NEED_RESCHED_LAZY);
#else
return unlikely(!raw_cpu_read_4(__preempt_count));
#endif
--
2.8.1