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Date: Thu, 23 Sep 2021 18:54:35 +0200 (CEST)
From: Thomas Gleixner <tglx@...utronix.de>
To: LKML <linux-kernel@...r.kernel.org>
Cc: Peter Zijlstra <peterz@...radead.org>,
Ingo Molnar <mingo@...nel.org>,
Paul McKenney <paulmck@...ux.vnet.ibm.com>,
Sebastian Siewior <bigeasy@...utronix.de>
Subject: [patch 1/8] sched: Clean up the might_sleep() underscore zoo
__might_sleep() vs. ___might_sleep() is hard to distinguish. Aside of that
the three underscore variant is exposed to provide a checkpoint for
rescheduling points which are distinct from blocking points.
They are semantically a preemption point which means that scheduling is
state preserving. A real blocking operation, e.g. mutex_lock(), wait*(),
which cannot preserve a task state which is not equal to RUNNING.
While technically blocking on a "sleeping" spinlock in RT enabled kernels
falls into the voluntary scheduling category because it has to wait until
the contended spin/rw lock becomes available, the RT lock substitution code
can semantically be mapped to a voluntary preemption because the RT lock
substitution code and the scheduler are providing mechanisms to preserve
the task state and to take regular non-lock related wakeups into account.
Rename ___might_sleep() to __might_resched() to make the distinction of
these functions clear.
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
---
include/linux/kernel.h | 6 +++---
include/linux/sched.h | 8 ++++----
kernel/locking/spinlock_rt.c | 6 +++---
kernel/sched/core.c | 6 +++---
4 files changed, 13 insertions(+), 13 deletions(-)
--- a/include/linux/kernel.h
+++ b/include/linux/kernel.h
@@ -111,7 +111,7 @@ static __always_inline void might_resche
#endif /* CONFIG_PREEMPT_* */
#ifdef CONFIG_DEBUG_ATOMIC_SLEEP
-extern void ___might_sleep(const char *file, int line, int preempt_offset);
+extern void __might_resched(const char *file, int line, int preempt_offset);
extern void __might_sleep(const char *file, int line, int preempt_offset);
extern void __cant_sleep(const char *file, int line, int preempt_offset);
extern void __cant_migrate(const char *file, int line);
@@ -168,8 +168,8 @@ extern void __cant_migrate(const char *f
*/
# define non_block_end() WARN_ON(current->non_block_count-- == 0)
#else
- static inline void ___might_sleep(const char *file, int line,
- int preempt_offset) { }
+ static inline void __might_resched(const char *file, int line,
+ int preempt_offset) { }
static inline void __might_sleep(const char *file, int line,
int preempt_offset) { }
# define might_sleep() do { might_resched(); } while (0)
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -2041,7 +2041,7 @@ static inline int _cond_resched(void) {
#endif /* !defined(CONFIG_PREEMPTION) || defined(CONFIG_PREEMPT_DYNAMIC) */
#define cond_resched() ({ \
- ___might_sleep(__FILE__, __LINE__, 0); \
+ __might_resched(__FILE__, __LINE__, 0); \
_cond_resched(); \
})
@@ -2049,9 +2049,9 @@ extern int __cond_resched_lock(spinlock_
extern int __cond_resched_rwlock_read(rwlock_t *lock);
extern int __cond_resched_rwlock_write(rwlock_t *lock);
-#define cond_resched_lock(lock) ({ \
- ___might_sleep(__FILE__, __LINE__, PREEMPT_LOCK_OFFSET);\
- __cond_resched_lock(lock); \
+#define cond_resched_lock(lock) ({ \
+ __might_resched(__FILE__, __LINE__, PREEMPT_LOCK_OFFSET); \
+ __cond_resched_lock(lock); \
})
#define cond_resched_rwlock_read(lock) ({ \
--- a/kernel/locking/spinlock_rt.c
+++ b/kernel/locking/spinlock_rt.c
@@ -32,7 +32,7 @@ static __always_inline void rtlock_lock(
static __always_inline void __rt_spin_lock(spinlock_t *lock)
{
- ___might_sleep(__FILE__, __LINE__, 0);
+ __might_resched(__FILE__, __LINE__, 0);
rtlock_lock(&lock->lock);
rcu_read_lock();
migrate_disable();
@@ -210,7 +210,7 @@ EXPORT_SYMBOL(rt_write_trylock);
void __sched rt_read_lock(rwlock_t *rwlock)
{
- ___might_sleep(__FILE__, __LINE__, 0);
+ __might_resched(__FILE__, __LINE__, 0);
rwlock_acquire_read(&rwlock->dep_map, 0, 0, _RET_IP_);
rwbase_read_lock(&rwlock->rwbase, TASK_RTLOCK_WAIT);
rcu_read_lock();
@@ -220,7 +220,7 @@ EXPORT_SYMBOL(rt_read_lock);
void __sched rt_write_lock(rwlock_t *rwlock)
{
- ___might_sleep(__FILE__, __LINE__, 0);
+ __might_resched(__FILE__, __LINE__, 0);
rwlock_acquire(&rwlock->dep_map, 0, 0, _RET_IP_);
rwbase_write_lock(&rwlock->rwbase, TASK_RTLOCK_WAIT);
rcu_read_lock();
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -9446,11 +9446,11 @@ void __might_sleep(const char *file, int
(void *)current->task_state_change,
(void *)current->task_state_change);
- ___might_sleep(file, line, preempt_offset);
+ __might_resched(file, line, preempt_offset);
}
EXPORT_SYMBOL(__might_sleep);
-void ___might_sleep(const char *file, int line, int preempt_offset)
+void __might_resched(const char *file, int line, int preempt_offset)
{
/* Ratelimiting timestamp: */
static unsigned long prev_jiffy;
@@ -9495,7 +9495,7 @@ void ___might_sleep(const char *file, in
dump_stack();
add_taint(TAINT_WARN, LOCKDEP_STILL_OK);
}
-EXPORT_SYMBOL(___might_sleep);
+EXPORT_SYMBOL(__might_resched);
void __cant_sleep(const char *file, int line, int preempt_offset)
{
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