| From | Thomas Gleixner <> | Subject | [patch V5 32/72] locking/rtmutex: Provide the spin/rwlock core lock function | Date | Sun, 15 Aug 2021 23:28:25 +0200 (CEST) |
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From: Thomas Gleixner <tglx@linutronix.de>
A simplified version of the rtmutex slowlock function which neither handles signals nor timeouts and is careful about preserving the state of the blocked task across the lock operation.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de> --- kernel/locking/rtmutex.c | 60 ++++++++++++++++++++++++++++++++++++++++ kernel/locking/rtmutex_common.h | 2 - 2 files changed, 61 insertions(+), 1 deletion(-) --- --- a/kernel/locking/rtmutex.c +++ b/kernel/locking/rtmutex.c @@ -1416,3 +1416,63 @@ static __always_inline int __rt_mutex_lo return rt_mutex_slowlock(lock, state); } #endif /* RT_MUTEX_BUILD_MUTEX */ + +#ifdef RT_MUTEX_BUILD_SPINLOCKS +/* + * Functions required for spin/rw_lock substitution on RT kernels + */ + +/** + * rtlock_slowlock_locked - Slow path lock acquisition for RT locks + * @lock: The underlying rt mutex + */ +static void __sched rtlock_slowlock_locked(struct rt_mutex_base *lock) +{ + struct rt_mutex_waiter waiter; + + lockdep_assert_held(&lock->wait_lock); + + if (try_to_take_rt_mutex(lock, current, NULL)) + return; + + rt_mutex_init_rtlock_waiter(&waiter); + + /* Save current state and set state to TASK_RTLOCK_WAIT */ + current_save_and_set_rtlock_wait_state(); + + task_blocks_on_rt_mutex(lock, &waiter, current, RT_MUTEX_MIN_CHAINWALK); + + for (;;) { + /* Try to acquire the lock again. */ + if (try_to_take_rt_mutex(lock, current, &waiter)) + break; + + raw_spin_unlock_irq(&lock->wait_lock); + + schedule_rtlock(); + + raw_spin_lock_irq(&lock->wait_lock); + set_current_state(TASK_RTLOCK_WAIT); + } + + /* Restore the task state */ + current_restore_rtlock_saved_state(); + + /* + * try_to_take_rt_mutex() sets the waiter bit unconditionally. We + * might have to fix that up: + */ + fixup_rt_mutex_waiters(lock); + debug_rt_mutex_free_waiter(&waiter); +} + +static __always_inline void __sched rtlock_slowlock(struct rt_mutex_base *lock) +{ + unsigned long flags; + + raw_spin_lock_irqsave(&lock->wait_lock, flags); + rtlock_slowlock_locked(lock); + raw_spin_unlock_irqrestore(&lock->wait_lock, flags); +} + +#endif /* RT_MUTEX_BUILD_SPINLOCKS */ --- a/kernel/locking/rtmutex_common.h +++ b/kernel/locking/rtmutex_common.h @@ -181,7 +181,7 @@ static inline void rt_mutex_init_waiter( waiter->task = NULL; } -static inline void rtlock_init_rtmutex_waiter(struct rt_mutex_waiter *waiter) +static inline void rt_mutex_init_rtlock_waiter(struct rt_mutex_waiter *waiter) { rt_mutex_init_waiter(waiter); waiter->wake_state = TASK_RTLOCK_WAIT;
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