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Message-ID: <20230223123319.608133045@infradead.org>
Date: Thu, 23 Feb 2023 13:26:47 +0100
From: Peter Zijlstra <peterz@...radead.org>
To: longman@...hat.com, mingo@...hat.com, will@...nel.org
Cc: linux-kernel@...r.kernel.org, peterz@...radead.org,
boqun.feng@...il.com
Subject: [PATCH 5/6] locking/rwsem: Unify wait loop
Now that the reader and writer wait loops are identical, share the
code.
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
---
kernel/locking/rwsem.c | 117 +++++++++++++++++++------------------------------
1 file changed, 47 insertions(+), 70 deletions(-)
--- a/kernel/locking/rwsem.c
+++ b/kernel/locking/rwsem.c
@@ -650,13 +650,11 @@ static void rwsem_mark_wake(struct rw_se
* optionally wake up waiters before it returns.
*/
static inline void
-rwsem_del_wake_waiter(struct rw_semaphore *sem, struct rwsem_waiter *waiter,
- struct wake_q_head *wake_q)
+rwsem_del_wake_waiter(struct rw_semaphore *sem, struct rwsem_waiter *waiter)
__releases(&sem->wait_lock)
{
bool first = rwsem_first_waiter(sem) == waiter;
-
- wake_q_init(wake_q);
+ DEFINE_WAKE_Q(wake_q);
/*
* If the wait_list isn't empty and the waiter to be deleted is
@@ -664,10 +662,10 @@ rwsem_del_wake_waiter(struct rw_semaphor
* be eligible to acquire or spin on the lock.
*/
if (rwsem_del_waiter(sem, waiter) && first)
- rwsem_mark_wake(sem, RWSEM_WAKE_ANY, wake_q);
+ rwsem_mark_wake(sem, RWSEM_WAKE_ANY, &wake_q);
raw_spin_unlock_irq(&sem->wait_lock);
- if (!wake_q_empty(wake_q))
- wake_up_q(wake_q);
+ if (!wake_q_empty(&wake_q))
+ wake_up_q(&wake_q);
}
/*
@@ -993,6 +991,46 @@ static inline void rwsem_cond_wake_waite
rwsem_mark_wake(sem, wake_type, wake_q);
}
+#define waiter_type(_waiter, _r, _w) \
+ ((_waiter)->type == RWSEM_WAITING_FOR_READ ? (_r) : (_w))
+
+static __always_inline struct rw_semaphore *
+rwsem_waiter_wait(struct rw_semaphore *sem, struct rwsem_waiter *waiter, int state)
+{
+ trace_contention_begin(sem, waiter_type(waiter, LCB_F_READ, LCB_F_WRITE));
+
+ /* wait to be given the lock */
+ for (;;) {
+ set_current_state(state);
+ if (!smp_load_acquire(&waiter->task)) {
+ /* Matches rwsem_waiter_wake()'s smp_store_release(). */
+ break;
+ }
+ if (signal_pending_state(state, current)) {
+ raw_spin_lock_irq(&sem->wait_lock);
+ if (waiter->task)
+ goto out_nolock;
+ raw_spin_unlock_irq(&sem->wait_lock);
+ /* Ordered by sem->wait_lock against rwsem_mark_wake(). */
+ break;
+ }
+ schedule_preempt_disabled();
+ lockevent_inc(waiter_type(waiter, rwsem_sleep_reader, rwsem_sleep_writer));
+ }
+
+ __set_current_state(TASK_RUNNING);
+ lockevent_inc(waiter_type(waiter, rwsem_rlock, rwsem_wlock));
+ trace_contention_end(sem, 0);
+ return sem;
+
+out_nolock:
+ rwsem_del_wake_waiter(sem, waiter);
+ __set_current_state(TASK_RUNNING);
+ lockevent_inc(waiter_type(waiter, rwsem_rlock_fail, rwsem_wlock_fail));
+ trace_contention_end(sem, -EINTR);
+ return ERR_PTR(-EINTR);
+}
+
/*
* Wait for the read lock to be granted
*/
@@ -1071,38 +1109,7 @@ rwsem_down_read_slowpath(struct rw_semap
if (!wake_q_empty(&wake_q))
wake_up_q(&wake_q);
- trace_contention_begin(sem, LCB_F_READ);
-
- /* wait to be given the lock */
- for (;;) {
- set_current_state(state);
- if (!smp_load_acquire(&waiter.task)) {
- /* Matches rwsem_waiter_wake()'s smp_store_release(). */
- break;
- }
- if (signal_pending_state(state, current)) {
- raw_spin_lock_irq(&sem->wait_lock);
- if (waiter.task)
- goto out_nolock;
- raw_spin_unlock_irq(&sem->wait_lock);
- /* Ordered by sem->wait_lock against rwsem_mark_wake(). */
- break;
- }
- schedule_preempt_disabled();
- lockevent_inc(rwsem_sleep_reader);
- }
-
- __set_current_state(TASK_RUNNING);
- lockevent_inc(rwsem_rlock);
- trace_contention_end(sem, 0);
- return sem;
-
-out_nolock:
- rwsem_del_wake_waiter(sem, &waiter, &wake_q);
- __set_current_state(TASK_RUNNING);
- lockevent_inc(rwsem_rlock_fail);
- trace_contention_end(sem, -EINTR);
- return ERR_PTR(-EINTR);
+ return rwsem_waiter_wait(sem, &waiter, state);
}
/*
@@ -1150,37 +1157,7 @@ rwsem_down_write_slowpath(struct rw_sema
}
raw_spin_unlock_irq(&sem->wait_lock);
- /* wait until we successfully acquire the lock */
- trace_contention_begin(sem, LCB_F_WRITE);
-
- for (;;) {
- set_current_state(state);
- if (!smp_load_acquire(&waiter.task)) {
- /* Matches rwsem_waiter_wake()'s smp_store_release(). */
- break;
- }
- if (signal_pending_state(state, current)) {
- raw_spin_lock_irq(&sem->wait_lock);
- if (waiter.task)
- goto out_nolock;
- raw_spin_unlock_irq(&sem->wait_lock);
- /* Ordered by sem->wait_lock against rwsem_mark_wake(). */
- break;
- }
- schedule_preempt_disabled();
- lockevent_inc(rwsem_sleep_writer);
- }
- __set_current_state(TASK_RUNNING);
- lockevent_inc(rwsem_wlock);
- trace_contention_end(sem, 0);
- return sem;
-
-out_nolock:
- rwsem_del_wake_waiter(sem, &waiter, &wake_q);
- __set_current_state(TASK_RUNNING);
- lockevent_inc(rwsem_wlock_fail);
- trace_contention_end(sem, -EINTR);
- return ERR_PTR(-EINTR);
+ return rwsem_waiter_wait(sem, &waiter, state);
}
/*
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