From bcc9a76d5ac426bc45c9e863b1830347827ca77a Mon Sep 17 00:00:00 2001 From: Waiman Long Date: Sat, 21 Jan 2017 21:33:35 -0500 Subject: [PATCH] locking/rwsem: Reinit wake_q after use In __rwsem_down_write_failed_common(), the same wake_q variable name is defined twice, with the inner wake_q hiding the one in outer scope. We can either use different names for the two wake_q's. Even better, we can use the same wake_q twice, if necessary. To enable the latter change, we need to define a new helper function wake_q_init() to enable reinitalization of wake_q after use. Signed-off-by: Waiman Long Cc: Andrew Morton Cc: Davidlohr Bueso Cc: Linus Torvalds Cc: Paul E. McKenney Cc: Peter Zijlstra Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/1485052415-9611-1-git-send-email-longman@redhat.com Signed-off-by: Ingo Molnar --- include/linux/sched.h | 6 ++++++ kernel/locking/rwsem-xadd.c | 7 +++++-- 2 files changed, 11 insertions(+), 2 deletions(-) diff --git a/include/linux/sched.h b/include/linux/sched.h index f4f9d32f12b3..4e62b378bd65 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -1021,6 +1021,12 @@ struct wake_q_head { #define DEFINE_WAKE_Q(name) \ struct wake_q_head name = { WAKE_Q_TAIL, &name.first } +static inline void wake_q_init(struct wake_q_head *head) +{ + head->first = WAKE_Q_TAIL; + head->lastp = &head->first; +} + extern void wake_q_add(struct wake_q_head *head, struct task_struct *task); extern void wake_up_q(struct wake_q_head *head); diff --git a/kernel/locking/rwsem-xadd.c b/kernel/locking/rwsem-xadd.c index a3a381aee24b..2ad8d8dc3bb1 100644 --- a/kernel/locking/rwsem-xadd.c +++ b/kernel/locking/rwsem-xadd.c @@ -502,8 +502,6 @@ __rwsem_down_write_failed_common(struct rw_semaphore *sem, int state) * wake any read locks that were queued ahead of us. */ if (count > RWSEM_WAITING_BIAS) { - DEFINE_WAKE_Q(wake_q); - __rwsem_mark_wake(sem, RWSEM_WAKE_READERS, &wake_q); /* * The wakeup is normally called _after_ the wait_lock @@ -513,6 +511,11 @@ __rwsem_down_write_failed_common(struct rw_semaphore *sem, int state) * for attempting rwsem_try_write_lock(). */ wake_up_q(&wake_q); + + /* + * Reinitialize wake_q after use. + */ + wake_q_init(&wake_q); } } else -- 2.20.1