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sched: Clean up the might_sleep() underscore zoo

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__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
This commit is contained in:
Thomas Gleixner 2021-09-23 18:54:35 +02:00 committed by Peter Zijlstra
parent 1415b49bcd
commit 874f670e60
4 changed files with 13 additions and 13 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

6
include/linux/kernel.h
View File

@ -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)

8
include/linux/sched.h
View File

@ -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) ({ \

6
kernel/locking/spinlock_rt.c
View File

@ -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();

6
kernel/sched/core.c
View File

@ -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)
{