From d47996082f52baa0ca8b48d26b3cbef5ede70a73 Mon Sep 17 00:00:00 2001 From: Michal Hocko Date: Thu, 7 Apr 2016 17:12:26 +0200 Subject: [PATCH] locking/rwsem: Introduce basis for down_write_killable() Introduce a generic implementation necessary for down_write_killable(). This is a trivial extension of the already existing down_write() call which can be interrupted by SIGKILL. This patch doesn't provide down_write_killable() yet because arches have to provide the necessary pieces before. rwsem_down_write_failed() which is a generic slow path for the write lock is extended to take a task state and renamed to __rwsem_down_write_failed_common(). The return value is either a valid semaphore pointer or ERR_PTR(-EINTR). rwsem_down_write_failed_killable() is exported as a new way to wait for the lock and be killable. For rwsem-spinlock implementation the current __down_write() it updated in a similar way as __rwsem_down_write_failed_common() except it doesn't need new exports just visible __down_write_killable(). Architectures which are not using the generic rwsem implementation are supposed to provide their __down_write_killable() implementation and use rwsem_down_write_failed_killable() for the slow path. Signed-off-by: Michal Hocko Cc: Andrew Morton Cc: Chris Zankel Cc: David S. Miller Cc: Linus Torvalds Cc: Max Filippov Cc: Paul E. McKenney Cc: Peter Zijlstra Cc: Signed-off-by: Davidlohr Bueso Cc: Signed-off-by: Jason Low Cc: Thomas Gleixner Cc: Tony Luck Cc: linux-alpha@vger.kernel.org Cc: linux-arch@vger.kernel.org Cc: linux-ia64@vger.kernel.org Cc: linux-s390@vger.kernel.org Cc: linux-sh@vger.kernel.org Cc: linux-xtensa@linux-xtensa.org Cc: sparclinux@vger.kernel.org Link: http://lkml.kernel.org/r/1460041951-22347-7-git-send-email-mhocko@kernel.org Signed-off-by: Ingo Molnar --- include/asm-generic/rwsem.h | 12 ++++++++++++ include/linux/rwsem-spinlock.h | 1 + include/linux/rwsem.h | 2 ++ kernel/locking/rwsem-spinlock.c | 22 ++++++++++++++++++++-- kernel/locking/rwsem-xadd.c | 31 +++++++++++++++++++++++++------ 5 files changed, 60 insertions(+), 8 deletions(-) diff --git a/include/asm-generic/rwsem.h b/include/asm-generic/rwsem.h index b8d8a6cf4ca8..3fc94a046bf5 100644 --- a/include/asm-generic/rwsem.h +++ b/include/asm-generic/rwsem.h @@ -63,6 +63,18 @@ static inline void __down_write(struct rw_semaphore *sem) rwsem_down_write_failed(sem); } +static inline int __down_write_killable(struct rw_semaphore *sem) +{ + long tmp; + + tmp = atomic_long_add_return_acquire(RWSEM_ACTIVE_WRITE_BIAS, + (atomic_long_t *)&sem->count); + if (unlikely(tmp != RWSEM_ACTIVE_WRITE_BIAS)) + if (IS_ERR(rwsem_down_write_failed_killable(sem))) + return -EINTR; + return 0; +} + static inline int __down_write_trylock(struct rw_semaphore *sem) { long tmp; diff --git a/include/linux/rwsem-spinlock.h b/include/linux/rwsem-spinlock.h index a733a5467e6c..ae0528b834cd 100644 --- a/include/linux/rwsem-spinlock.h +++ b/include/linux/rwsem-spinlock.h @@ -34,6 +34,7 @@ struct rw_semaphore { extern void __down_read(struct rw_semaphore *sem); extern int __down_read_trylock(struct rw_semaphore *sem); extern void __down_write(struct rw_semaphore *sem); +extern int __must_check __down_write_killable(struct rw_semaphore *sem); extern int __down_write_trylock(struct rw_semaphore *sem); extern void __up_read(struct rw_semaphore *sem); extern void __up_write(struct rw_semaphore *sem); diff --git a/include/linux/rwsem.h b/include/linux/rwsem.h index 8f498cdde280..7d7ae029dac5 100644 --- a/include/linux/rwsem.h +++ b/include/linux/rwsem.h @@ -14,6 +14,7 @@ #include #include #include +#include #ifdef CONFIG_RWSEM_SPIN_ON_OWNER #include #endif @@ -43,6 +44,7 @@ struct rw_semaphore { extern struct rw_semaphore *rwsem_down_read_failed(struct rw_semaphore *sem); extern struct rw_semaphore *rwsem_down_write_failed(struct rw_semaphore *sem); +extern struct rw_semaphore *rwsem_down_write_failed_killable(struct rw_semaphore *sem); extern struct rw_semaphore *rwsem_wake(struct rw_semaphore *); extern struct rw_semaphore *rwsem_downgrade_wake(struct rw_semaphore *sem); diff --git a/kernel/locking/rwsem-spinlock.c b/kernel/locking/rwsem-spinlock.c index bab26104a5d0..1591f6b3539f 100644 --- a/kernel/locking/rwsem-spinlock.c +++ b/kernel/locking/rwsem-spinlock.c @@ -191,11 +191,12 @@ int __down_read_trylock(struct rw_semaphore *sem) /* * get a write lock on the semaphore */ -void __sched __down_write(struct rw_semaphore *sem) +int __sched __down_write_common(struct rw_semaphore *sem, int state) { struct rwsem_waiter waiter; struct task_struct *tsk; unsigned long flags; + int ret = 0; raw_spin_lock_irqsave(&sem->wait_lock, flags); @@ -215,16 +216,33 @@ void __sched __down_write(struct rw_semaphore *sem) */ if (sem->count == 0) break; - set_task_state(tsk, TASK_UNINTERRUPTIBLE); + if (signal_pending_state(state, current)) { + ret = -EINTR; + goto out; + } + set_task_state(tsk, state); raw_spin_unlock_irqrestore(&sem->wait_lock, flags); schedule(); raw_spin_lock_irqsave(&sem->wait_lock, flags); } /* got the lock */ sem->count = -1; +out: list_del(&waiter.list); raw_spin_unlock_irqrestore(&sem->wait_lock, flags); + + return ret; +} + +void __sched __down_write(struct rw_semaphore *sem) +{ + __down_write_common(sem, TASK_UNINTERRUPTIBLE); +} + +int __sched __down_write_killable(struct rw_semaphore *sem) +{ + return __down_write_common(sem, TASK_KILLABLE); } /* diff --git a/kernel/locking/rwsem-xadd.c b/kernel/locking/rwsem-xadd.c index a4d4de05b2d1..df4dcb883b50 100644 --- a/kernel/locking/rwsem-xadd.c +++ b/kernel/locking/rwsem-xadd.c @@ -433,12 +433,13 @@ static inline bool rwsem_has_spinner(struct rw_semaphore *sem) /* * Wait until we successfully acquire the write lock */ -__visible -struct rw_semaphore __sched *rwsem_down_write_failed(struct rw_semaphore *sem) +static inline struct rw_semaphore * +__rwsem_down_write_failed_common(struct rw_semaphore *sem, int state) { long count; bool waiting = true; /* any queued threads before us */ struct rwsem_waiter waiter; + struct rw_semaphore *ret = sem; /* undo write bias from down_write operation, stop active locking */ count = rwsem_atomic_update(-RWSEM_ACTIVE_WRITE_BIAS, sem); @@ -478,7 +479,7 @@ struct rw_semaphore __sched *rwsem_down_write_failed(struct rw_semaphore *sem) count = rwsem_atomic_update(RWSEM_WAITING_BIAS, sem); /* wait until we successfully acquire the lock */ - set_current_state(TASK_UNINTERRUPTIBLE); + set_current_state(state); while (true) { if (rwsem_try_write_lock(count, sem)) break; @@ -486,21 +487,39 @@ struct rw_semaphore __sched *rwsem_down_write_failed(struct rw_semaphore *sem) /* Block until there are no active lockers. */ do { + if (signal_pending_state(state, current)) { + raw_spin_lock_irq(&sem->wait_lock); + ret = ERR_PTR(-EINTR); + goto out; + } schedule(); - set_current_state(TASK_UNINTERRUPTIBLE); + set_current_state(state); } while ((count = sem->count) & RWSEM_ACTIVE_MASK); raw_spin_lock_irq(&sem->wait_lock); } +out: __set_current_state(TASK_RUNNING); - list_del(&waiter.list); raw_spin_unlock_irq(&sem->wait_lock); - return sem; + return ret; +} + +__visible struct rw_semaphore * __sched +rwsem_down_write_failed(struct rw_semaphore *sem) +{ + return __rwsem_down_write_failed_common(sem, TASK_UNINTERRUPTIBLE); } EXPORT_SYMBOL(rwsem_down_write_failed); +__visible struct rw_semaphore * __sched +rwsem_down_write_failed_killable(struct rw_semaphore *sem) +{ + return __rwsem_down_write_failed_common(sem, TASK_KILLABLE); +} +EXPORT_SYMBOL(rwsem_down_write_failed_killable); + /* * handle waking up a waiter on the semaphore * - up_read/up_write has decremented the active part of count if we come here -- 2.20.1