Ingo requested I keep my debug check for the preempt_count invariant.
Requested-by: Ingo Molnar <mi...@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <pet...@infradead.org>
---
include/asm-generic/preempt.h | 2 +-
include/linux/sched.h | 17 +++++++++--------
kernel/sched/core.c | 5 +++++
3 files changed, 15 insertions(+), 9 deletions(-)
--- a/include/asm-generic/preempt.h
+++ b/include/asm-generic/preempt.h
@@ -24,7 +24,7 @@ static __always_inline void preempt_coun
* must be macros to avoid header recursion hell
*/
#define init_task_preempt_count(p) do { \
- task_thread_info(p)->preempt_count = 2*PREEMPT_DISABLED; \
+ task_thread_info(p)->preempt_count = INIT_PREEMPT_COUNT; \
} while (0)
#define init_idle_preempt_count(p, cpu) do { \
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -599,17 +599,18 @@ struct task_cputime_atomic {
.sum_exec_runtime = ATOMIC64_INIT(0), \
}
-#ifdef CONFIG_PREEMPT_COUNT
-#define PREEMPT_DISABLED (1 + PREEMPT_ENABLED)
-#else
-#define PREEMPT_DISABLED PREEMPT_ENABLED
-#endif
+#define PREEMPT_DISABLED (PREEMPT_DISABLE_OFFSET + PREEMPT_ENABLED)
/*
- * Disable preemption until the scheduler is running.
- * Reset by start_kernel()->sched_init()->init_idle().
+ * Initial preempt_count value; reflects the preempt_count schedule invariant
+ * which states that during schedule preempt_count() == 2.
+ *
+ * This also results in the kernel starting with preemption disabled until
+ * the scheduler is initialized, see:
+ *
+ * start_kernel()->sched_init()->init_idle().
*/
-#define INIT_PREEMPT_COUNT PREEMPT_DISABLED
+#define INIT_PREEMPT_COUNT (2*PREEMPT_DISABLE_OFFSET + PREEMPT_ENABLED)
/**
* struct thread_group_cputimer - thread group interval timer counts
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -2503,6 +2503,11 @@ static struct rq *finish_task_switch(str
struct mm_struct *mm = rq->prev_mm;
long prev_state;
+ if (unlikely(WARN_ONCE(preempt_count() != 2*PREEMPT_DISABLE_OFFSET,
+ "corrupted preempt_count: %s/%d/0x%x\n",
+ current->comm, current->pid, preempt_count())))
+ preempt_count_set(INIT_PREEMPT_COUNT);
+
rq->prev_mm = NULL;
/*
--
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