Commit 2d7d253548cffdce80f4e03664686e9ccb1b0ed7 ("fix cond_resched() fix")
introduced an 'expected_preempt_count' parameter to __resched_legal() to fix
a bug where it was returning a false negative when called from
cond_resched_lock() and preemption was enabled.
Unfortunately this broke things for when preemption is disabled.
preempt_count() will always return zero, thus failing the check against
any value of expected_preempt_count not equal to zero. cond_resched_lock()
for example, passes an expected_preempt_count value of 1.
So fix the fix for the cond_resched() fix by skipping the check of
preempt_count() against expected_preempt_count when preemption is disabled.
Credit should go to Sunil Mushran for spotting the bug during testing.
Signed-off-by: Mark Fasheh <[email protected]>
---
kernel/sched.c | 2 ++
1 files changed, 2 insertions(+), 0 deletions(-)
diff --git a/kernel/sched.c b/kernel/sched.c
index 8a0afb9..82b971f 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -4616,8 +4616,10 @@ asmlinkage long sys_sched_yield(void)
static inline int __resched_legal(int expected_preempt_count)
{
+#ifdef CONFIG_PREEMPT
if (unlikely(preempt_count() != expected_preempt_count))
return 0;
+#endif
if (unlikely(system_state != SYSTEM_RUNNING))
return 0;
return 1;
--
1.4.2.4
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