From 3a9320ecb06c6c5ca5a8a595717e5186b5f20141 Mon Sep 17 00:00:00 2001 From: Juri Lelli Date: Wed, 9 Oct 2024 16:53:36 -0700 Subject: [PATCH] locking/mutex: Expose __mutex_owner() Implementing proxy execution requires that scheduler code be able to identify the current owner of a mutex. Expose __mutex_owner() for this purpose (alone!). Includes a null mutex check, so that users of the function can be simplified. [Removed the EXPORT_SYMBOL] [jstultz: Reworked per Peter's suggestions] Signed-off-by: Juri Lelli Signed-off-by: Valentin Schneider Signed-off-by: Connor O'Brien Signed-off-by: John Stultz Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Metin Kaya Reviewed-by: Valentin Schneider Tested-by: K Prateek Nayak Tested-by: Metin Kaya Link: https://lore.kernel.org/r/20241009235352.1614323-4-jstultz@google.com --- kernel/locking/mutex.c | 25 ------------------------- kernel/locking/mutex.h | 27 +++++++++++++++++++++++++++ 2 files changed, 27 insertions(+), 25 deletions(-) diff --git a/kernel/locking/mutex.c b/kernel/locking/mutex.c index cd248d1767eb..3302e52f0c96 100644 --- a/kernel/locking/mutex.c +++ b/kernel/locking/mutex.c @@ -56,31 +56,6 @@ __mutex_init(struct mutex *lock, const char *name, struct lock_class_key *key) } EXPORT_SYMBOL(__mutex_init); -/* - * @owner: contains: 'struct task_struct *' to the current lock owner, - * NULL means not owned. Since task_struct pointers are aligned at - * at least L1_CACHE_BYTES, we have low bits to store extra state. - * - * Bit0 indicates a non-empty waiter list; unlock must issue a wakeup. - * Bit1 indicates unlock needs to hand the lock to the top-waiter - * Bit2 indicates handoff has been done and we're waiting for pickup. - */ -#define MUTEX_FLAG_WAITERS 0x01 -#define MUTEX_FLAG_HANDOFF 0x02 -#define MUTEX_FLAG_PICKUP 0x04 - -#define MUTEX_FLAGS 0x07 - -/* - * Internal helper function; C doesn't allow us to hide it :/ - * - * DO NOT USE (outside of mutex code). - */ -static inline struct task_struct *__mutex_owner(struct mutex *lock) -{ - return (struct task_struct *)(atomic_long_read(&lock->owner) & ~MUTEX_FLAGS); -} - static inline struct task_struct *__owner_task(unsigned long owner) { return (struct task_struct *)(owner & ~MUTEX_FLAGS); diff --git a/kernel/locking/mutex.h b/kernel/locking/mutex.h index 0b2a79c4013b..cbff35b9b7ae 100644 --- a/kernel/locking/mutex.h +++ b/kernel/locking/mutex.h @@ -20,6 +20,33 @@ struct mutex_waiter { #endif }; +/* + * @owner: contains: 'struct task_struct *' to the current lock owner, + * NULL means not owned. Since task_struct pointers are aligned at + * at least L1_CACHE_BYTES, we have low bits to store extra state. + * + * Bit0 indicates a non-empty waiter list; unlock must issue a wakeup. + * Bit1 indicates unlock needs to hand the lock to the top-waiter + * Bit2 indicates handoff has been done and we're waiting for pickup. + */ +#define MUTEX_FLAG_WAITERS 0x01 +#define MUTEX_FLAG_HANDOFF 0x02 +#define MUTEX_FLAG_PICKUP 0x04 + +#define MUTEX_FLAGS 0x07 + +/* + * Internal helper function; C doesn't allow us to hide it :/ + * + * DO NOT USE (outside of mutex & scheduler code). + */ +static inline struct task_struct *__mutex_owner(struct mutex *lock) +{ + if (!lock) + return NULL; + return (struct task_struct *)(atomic_long_read(&lock->owner) & ~MUTEX_FLAGS); +} + #ifdef CONFIG_DEBUG_MUTEXES extern void debug_mutex_lock_common(struct mutex *lock, struct mutex_waiter *waiter); -- 2.50.1