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locking/local_lock: Introduce local_lock_is_locked().

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Introduce local_lock_is_locked() that returns true when
given local_lock is locked by current cpu (in !PREEMPT_RT) or
by current task (in PREEMPT_RT).
The goal is to detect a deadlock by the caller.

Reviewed-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
This commit is contained in:
Alexei Starovoitov
2025-09-08 18:00:02 -07:00
committed by Vlastimil Babka
parent 4ec1a08d20
commit 4957089a23
4 changed files with 19 additions and 9 deletions
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2
include/linux/local_lock.h
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@@ -66,6 +66,8 @@
*/ */
#define local_trylock(lock) __local_trylock(this_cpu_ptr(lock)) #define local_trylock(lock) __local_trylock(this_cpu_ptr(lock))
#define local_lock_is_locked(lock) __local_lock_is_locked(lock)
/** /**
* local_trylock_irqsave - Try to acquire a per CPU local lock, save and disable * local_trylock_irqsave - Try to acquire a per CPU local lock, save and disable
* interrupts if acquired * interrupts if acquired

7
include/linux/local_lock_internal.h
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@@ -165,6 +165,9 @@ do { \
!!tl; \ !!tl; \
}) })
/* preemption or migration must be disabled before calling __local_lock_is_locked */
#define __local_lock_is_locked(lock) READ_ONCE(this_cpu_ptr(lock)->acquired)
#define __local_lock_release(lock) \ #define __local_lock_release(lock) \
do { \ do { \
local_trylock_t *tl; \ local_trylock_t *tl; \
@@ -285,4 +288,8 @@ do { \
__local_trylock(lock); \ __local_trylock(lock); \
}) })
/* migration must be disabled before calling __local_lock_is_locked */
#define __local_lock_is_locked(__lock) \
(rt_mutex_owner(&this_cpu_ptr(__lock)->lock) == current)
#endif /* CONFIG_PREEMPT_RT */ #endif /* CONFIG_PREEMPT_RT */

10
include/linux/rtmutex.h
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@@ -44,6 +44,16 @@ static inline bool rt_mutex_base_is_locked(struct rt_mutex_base *lock)
return READ_ONCE(lock->owner) != NULL; return READ_ONCE(lock->owner) != NULL;
} }
#ifdef CONFIG_RT_MUTEXES
#define RT_MUTEX_HAS_WAITERS 1UL
static inline struct task_struct *rt_mutex_owner(struct rt_mutex_base *lock)
{
unsigned long owner = (unsigned long) READ_ONCE(lock->owner);
return (struct task_struct *) (owner & ~RT_MUTEX_HAS_WAITERS);
}
#endif
extern void rt_mutex_base_init(struct rt_mutex_base *rtb); extern void rt_mutex_base_init(struct rt_mutex_base *rtb);
/** /**

9
kernel/locking/rtmutex_common.h
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@@ -153,15 +153,6 @@ static inline struct rt_mutex_waiter *task_top_pi_waiter(struct task_struct *p)
pi_tree.entry); pi_tree.entry);
} }
#define RT_MUTEX_HAS_WAITERS 1UL
static inline struct task_struct *rt_mutex_owner(struct rt_mutex_base *lock)
{
unsigned long owner = (unsigned long) READ_ONCE(lock->owner);
return (struct task_struct *) (owner & ~RT_MUTEX_HAS_WAITERS);
}
/* /*
* Constants for rt mutex functions which have a selectable deadlock * Constants for rt mutex functions which have a selectable deadlock
* detection. * detection.