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@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20210923165357.928693482@linutronix.de

diff --git a/include/linux/kernel.h b/include/linux/kernel.h
index 2776423a587e4a1a999f26bd41b586f818ac15d5..5e4ae54da73e87febf81d91633c38e05c1bc4265 100644 (file)
--- a/include/linux/kernel.h
+++ b/include/linux/kernel.h
@@ -111,7 +111,7 @@ static __always_inline void might_resched(void)
 #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 *file, int line);
  */
 # 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)

diff --git a/include/linux/sched.h b/include/linux/sched.h
index e12b524426b0286be06751bb3ae891a5e55b055e..b38f002334d59537efc7e59a5be1dbd6a762b06b 100644 (file)
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -2038,7 +2038,7 @@ static inline int _cond_resched(void) { return 0; }
 #endif /* !defined(CONFIG_PREEMPTION) || defined(CONFIG_PREEMPT_DYNAMIC) */
 
 #define cond_resched() ({                      \
-       ___might_sleep(__FILE__, __LINE__, 0);  \
+       __might_resched(__FILE__, __LINE__, 0); \
        _cond_resched();                        \
 })
 
@@ -2046,9 +2046,9 @@ extern int __cond_resched_lock(spinlock_t *lock);
 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) ({                      \

diff --git a/kernel/locking/spinlock_rt.c b/kernel/locking/spinlock_rt.c
index d2912e44d61fdb10a761c18ed279deccff76a29d..c5289240cfb43c12a1bf678ec68947fb216abb28 100644 (file)
--- a/kernel/locking/spinlock_rt.c
+++ b/kernel/locking/spinlock_rt.c
@@ -32,7 +32,7 @@ static __always_inline void rtlock_lock(struct rt_mutex_base *rtm)
 
 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();

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 1bba4128a3e68b6a5db9fe5bcf7ff2cb760b0232..c3943aa2f60c1c4be583d5a0deb189338404a755 100644 (file)
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -9489,11 +9489,11 @@ void __might_sleep(const char *file, int line, int preempt_offset)
                        (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;
@@ -9538,7 +9538,7 @@ void ___might_sleep(const char *file, int line, int preempt_offset)
        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)
 {