From 31784cff7ee073b34d6eddabb95e3be2880a425c Mon Sep 17 00:00:00 2001 From: "Eric W. Biederman" Date: Thu, 3 Dec 2020 14:11:13 -0600 Subject: [PATCH] rwsem: Implement down_read_interruptible In preparation for converting exec_update_mutex to a rwsem so that multiple readers can execute in parallel and not deadlock, add down_read_interruptible. This is needed for perf_event_open to be converted (with no semantic changes) from working on a mutex to wroking on a rwsem. Signed-off-by: Eric W. Biederman Signed-off-by: Peter Zijlstra (Intel) Link: https://lkml.kernel.org/r/87k0tybqfy.fsf@x220.int.ebiederm.org --- include/linux/rwsem.h | 1 + kernel/locking/rwsem.c | 26 ++++++++++++++++++++++++++ 2 files changed, 27 insertions(+) diff --git a/include/linux/rwsem.h b/include/linux/rwsem.h index 13021b08b2ed..4c715be48717 100644 --- a/include/linux/rwsem.h +++ b/include/linux/rwsem.h @@ -123,6 +123,7 @@ static inline int rwsem_is_contended(struct rw_semaphore *sem) * lock for reading */ extern void down_read(struct rw_semaphore *sem); +extern int __must_check down_read_interruptible(struct rw_semaphore *sem); extern int __must_check down_read_killable(struct rw_semaphore *sem); /* diff --git a/kernel/locking/rwsem.c b/kernel/locking/rwsem.c index 54d11cb97551..a163542d178e 100644 --- a/kernel/locking/rwsem.c +++ b/kernel/locking/rwsem.c @@ -1345,6 +1345,18 @@ static inline void __down_read(struct rw_semaphore *sem) } } +static inline int __down_read_interruptible(struct rw_semaphore *sem) +{ + if (!rwsem_read_trylock(sem)) { + if (IS_ERR(rwsem_down_read_slowpath(sem, TASK_INTERRUPTIBLE))) + return -EINTR; + DEBUG_RWSEMS_WARN_ON(!is_rwsem_reader_owned(sem), sem); + } else { + rwsem_set_reader_owned(sem); + } + return 0; +} + static inline int __down_read_killable(struct rw_semaphore *sem) { if (!rwsem_read_trylock(sem)) { @@ -1495,6 +1507,20 @@ void __sched down_read(struct rw_semaphore *sem) } EXPORT_SYMBOL(down_read); +int __sched down_read_interruptible(struct rw_semaphore *sem) +{ + might_sleep(); + rwsem_acquire_read(&sem->dep_map, 0, 0, _RET_IP_); + + if (LOCK_CONTENDED_RETURN(sem, __down_read_trylock, __down_read_interruptible)) { + rwsem_release(&sem->dep_map, _RET_IP_); + return -EINTR; + } + + return 0; +} +EXPORT_SYMBOL(down_read_interruptible); + int __sched down_read_killable(struct rw_semaphore *sem) { might_sleep();