From: Yanfei Xu yanfei.xu@windriver.com
[ Upstream commit 7cdacc5f52d68a9370f182c844b5b3e6cc975cc1 ]
The spinning region rwsem_spin_on_owner() should not be preempted, however the rwsem_down_write_slowpath() invokes it and don't disable preemption. Fix it by adding a pair of preempt_disable/enable().
Signed-off-by: Yanfei Xu yanfei.xu@windriver.com [peterz: Fix CONFIG_RWSEM_SPIN_ON_OWNER=n build] Signed-off-by: Peter Zijlstra (Intel) peterz@infradead.org Acked-by: Waiman Long longman@redhat.com Link: https://lore.kernel.org/r/20211013134154.1085649-3-yanfei.xu@windriver.com Signed-off-by: Sasha Levin sashal@kernel.org --- kernel/locking/rwsem.c | 53 ++++++++++++++++++++++++------------------ 1 file changed, 30 insertions(+), 23 deletions(-)
diff --git a/kernel/locking/rwsem.c b/kernel/locking/rwsem.c index 000e8d5a28841..29eea50a3e678 100644 --- a/kernel/locking/rwsem.c +++ b/kernel/locking/rwsem.c @@ -577,6 +577,24 @@ static inline bool rwsem_try_write_lock(struct rw_semaphore *sem, return true; }
+/* + * The rwsem_spin_on_owner() function returns the following 4 values + * depending on the lock owner state. + * OWNER_NULL : owner is currently NULL + * OWNER_WRITER: when owner changes and is a writer + * OWNER_READER: when owner changes and the new owner may be a reader. + * OWNER_NONSPINNABLE: + * when optimistic spinning has to stop because either the + * owner stops running, is unknown, or its timeslice has + * been used up. + */ +enum owner_state { + OWNER_NULL = 1 << 0, + OWNER_WRITER = 1 << 1, + OWNER_READER = 1 << 2, + OWNER_NONSPINNABLE = 1 << 3, +}; + #ifdef CONFIG_RWSEM_SPIN_ON_OWNER /* * Try to acquire write lock before the writer has been put on wait queue. @@ -632,23 +650,6 @@ static inline bool rwsem_can_spin_on_owner(struct rw_semaphore *sem) return ret; }
-/* - * The rwsem_spin_on_owner() function returns the following 4 values - * depending on the lock owner state. - * OWNER_NULL : owner is currently NULL - * OWNER_WRITER: when owner changes and is a writer - * OWNER_READER: when owner changes and the new owner may be a reader. - * OWNER_NONSPINNABLE: - * when optimistic spinning has to stop because either the - * owner stops running, is unknown, or its timeslice has - * been used up. - */ -enum owner_state { - OWNER_NULL = 1 << 0, - OWNER_WRITER = 1 << 1, - OWNER_READER = 1 << 2, - OWNER_NONSPINNABLE = 1 << 3, -}; #define OWNER_SPINNABLE (OWNER_NULL | OWNER_WRITER | OWNER_READER)
static inline enum owner_state @@ -878,12 +879,11 @@ static inline bool rwsem_optimistic_spin(struct rw_semaphore *sem)
static inline void clear_nonspinnable(struct rw_semaphore *sem) { }
-static inline int +static inline enum owner_state rwsem_spin_on_owner(struct rw_semaphore *sem) { - return 0; + return OWNER_NONSPINNABLE; } -#define OWNER_NULL 1 #endif
/* @@ -1095,9 +1095,16 @@ wait: * In this case, we attempt to acquire the lock again * without sleeping. */ - if (wstate == WRITER_HANDOFF && - rwsem_spin_on_owner(sem) == OWNER_NULL) - goto trylock_again; + if (wstate == WRITER_HANDOFF) { + enum owner_state owner_state; + + preempt_disable(); + owner_state = rwsem_spin_on_owner(sem); + preempt_enable(); + + if (owner_state == OWNER_NULL) + goto trylock_again; + }
/* Block until there are no active lockers. */ for (;;) {