Messages in this thread Patch in this message | | | From | Waiman Long <> | Subject | [PATCH v2 5/8] locking/rwsem: Split out rwsem_reader_wake() | Date | Mon, 27 Mar 2023 16:24:10 -0400 |
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From: Peter Zijlstra <peterz@infradead.org>
To provide symmetry with rwsem_writer_wake().
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> --- kernel/locking/rwsem.c | 83 +++++++++++++++++++++++------------------- 1 file changed, 46 insertions(+), 37 deletions(-)
diff --git a/kernel/locking/rwsem.c b/kernel/locking/rwsem.c index 225e86326ea4..0bc262dc77fd 100644 --- a/kernel/locking/rwsem.c +++ b/kernel/locking/rwsem.c @@ -106,9 +106,9 @@ * atomic_long_cmpxchg() will be used to obtain writer lock. * * There are three places where the lock handoff bit may be set or cleared. - * 1) rwsem_mark_wake() for readers -- set, clear + * 1) rwsem_reader_wake() for readers -- set, clear * 2) rwsem_try_write_lock() for writers -- set, clear - * 3) rwsem_del_waiter() -- clear + * 3) rwsem_del_waiter() -- clear * * For all the above cases, wait_lock will be held. A writer must also * be the first one in the wait_list to be eligible for setting the handoff @@ -377,7 +377,7 @@ rwsem_add_waiter(struct rw_semaphore *sem, struct rwsem_waiter *waiter) /* * Remove a waiter from the wait_list and clear flags. * - * Both rwsem_mark_wake() and rwsem_try_write_lock() contain a full 'copy' of + * Both rwsem_reader_wake() and rwsem_try_write_lock() contain a full 'copy' of * this function. Modify with care. * * Return: true if wait_list isn't empty and false otherwise @@ -483,42 +483,15 @@ static void rwsem_writer_wake(struct rw_semaphore *sem, rwsem_waiter_wake(waiter, wake_q); } -/* - * handle the lock release when processes blocked on it that can now run - * - if we come here from up_xxxx(), then the RWSEM_FLAG_WAITERS bit must - * have been set. - * - there must be someone on the queue - * - the wait_lock must be held by the caller - * - tasks are marked for wakeup, the caller must later invoke wake_up_q() - * to actually wakeup the blocked task(s) and drop the reference count, - * preferably when the wait_lock is released - * - woken process blocks are discarded from the list after having task zeroed - * - writers are only marked woken if downgrading is false - * - * Implies rwsem_del_waiter() for all woken readers. - */ -static void rwsem_mark_wake(struct rw_semaphore *sem, - enum rwsem_wake_type wake_type, - struct wake_q_head *wake_q) +static void rwsem_reader_wake(struct rw_semaphore *sem, + enum rwsem_wake_type wake_type, + struct rwsem_waiter *waiter, + struct wake_q_head *wake_q) { - struct rwsem_waiter *waiter, *tmp; long count, woken = 0, adjustment = 0; + struct rwsem_waiter *tmp; struct list_head wlist; - lockdep_assert_held(&sem->wait_lock); - - /* - * Take a peek at the queue head waiter such that we can determine - * the wakeup(s) to perform. - */ - waiter = rwsem_first_waiter(sem); - - if (waiter->type == RWSEM_WAITING_FOR_WRITE) { - if (wake_type == RWSEM_WAKE_ANY) - rwsem_writer_wake(sem, waiter, wake_q); - return; - } - /* * No reader wakeup if there are too many of them already. */ @@ -634,6 +607,42 @@ static void rwsem_mark_wake(struct rw_semaphore *sem, rwsem_waiter_wake(waiter, wake_q); } +/* + * handle the lock release when processes blocked on it that can now run + * - if we come here from up_xxxx(), then the RWSEM_FLAG_WAITERS bit must + * have been set. + * - there must be someone on the queue + * - the wait_lock must be held by the caller + * - tasks are marked for wakeup, the caller must later invoke wake_up_q() + * to actually wakeup the blocked task(s) and drop the reference count, + * preferably when the wait_lock is released + * - woken process blocks are discarded from the list after having task zeroed + * - writers are only marked woken if downgrading is false + * + * Implies rwsem_del_waiter() for all woken waiters. + */ +static void rwsem_mark_wake(struct rw_semaphore *sem, + enum rwsem_wake_type wake_type, + struct wake_q_head *wake_q) +{ + struct rwsem_waiter *waiter; + + lockdep_assert_held(&sem->wait_lock); + + /* + * Take a peek at the queue head waiter such that we can determine + * the wakeup(s) to perform. + */ + waiter = rwsem_first_waiter(sem); + + if (waiter->type == RWSEM_WAITING_FOR_WRITE) { + if (wake_type == RWSEM_WAKE_ANY) + rwsem_writer_wake(sem, waiter, wake_q); + } else { + rwsem_reader_wake(sem, wake_type, waiter, wake_q); + } +} + /* * Remove a waiter and try to wake up other waiters in the wait queue * This function is called from the out_nolock path of both the reader and @@ -1022,8 +1031,8 @@ rwsem_down_read_slowpath(struct rw_semaphore *sem, long count, unsigned int stat if ((rcnt == 1) && (count & RWSEM_FLAG_WAITERS)) { raw_spin_lock_irq(&sem->wait_lock); if (!list_empty(&sem->wait_list)) - rwsem_mark_wake(sem, RWSEM_WAKE_READ_OWNED, - &wake_q); + rwsem_mark_wake(sem, RWSEM_WAKE_READ_OWNED, &wake_q); + raw_spin_unlock_irq(&sem->wait_lock); wake_up_q(&wake_q); } -- 2.31.1
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