On Tue, Mar 22, 2022 at 11:57:09AM -0700, Namhyung Kim wrote:
> Adding the lock contention tracepoints in various lock function slow
> paths. Note that each arch can define spinlock differently, I only
> added it only to the generic qspinlock for now.
>
> Tested-by: Hyeonggon Yoo <42.hyeyoo@xxxxxxxxx>
> Signed-off-by: Namhyung Kim <namhyung@xxxxxxxxxx>
> ---
> kernel/locking/mutex.c | 3 +++
> kernel/locking/percpu-rwsem.c | 3 +++
> kernel/locking/qrwlock.c | 9 +++++++++
> kernel/locking/qspinlock.c | 5 +++++
> kernel/locking/rtmutex.c | 11 +++++++++++
> kernel/locking/rwbase_rt.c | 3 +++
> kernel/locking/rwsem.c | 9 +++++++++
> kernel/locking/semaphore.c | 15 ++++++++++++++-
> 8 files changed, 57 insertions(+), 1 deletion(-)
I had conflicts in rwsem.c due to Waiman's patches, but that was simple
enough to resolve. However, I had a good look at the other sites and
ended up with the below...
Yes, I know I'm the one that suggested the percpu thing, but upon
looking again it missed the largest part of percpu_down_write(), which
very much includes that RCU grace period and waiting for the readers to
bugger off
Also, rwbase_rt was missing the entire READ side -- yes, I see that's
also covered by the rtmuex.c part, but that's on a different address and
with different flags, and it's very confusing to not have it annotated.
Anyway, I'll queue this patch with the below folded in for post -rc1.
---
--- a/kernel/locking/percpu-rwsem.c
+++ b/kernel/locking/percpu-rwsem.c
@@ -155,7 +155,6 @@ static void percpu_rwsem_wait(struct per
}
spin_unlock_irq(&sem->waiters.lock);
- trace_contention_begin(sem, LCB_F_PERCPU | (reader ? LCB_F_READ : LCB_F_WRITE));
while (wait) {
set_current_state(TASK_UNINTERRUPTIBLE);
if (!smp_load_acquire(&wq_entry.private))
@@ -163,7 +162,6 @@ static void percpu_rwsem_wait(struct per
schedule();
}
__set_current_state(TASK_RUNNING);
- trace_contention_end(sem, 0);
}
bool __sched __percpu_down_read(struct percpu_rw_semaphore *sem, bool try)
@@ -174,9 +172,11 @@ bool __sched __percpu_down_read(struct p
if (try)
return false;
+ trace_contention_begin(sem, LCB_F_PERCPU | LCB_F_READ);
preempt_enable();
percpu_rwsem_wait(sem, /* .reader = */ true);
preempt_disable();
+ trace_contention_end(sem, 0);
return true;
}
@@ -219,6 +219,7 @@ void __sched percpu_down_write(struct pe
{
might_sleep();
rwsem_acquire(&sem->dep_map, 0, 0, _RET_IP_);
+ trace_contention_begin(sem, LCB_F_PERCPU | LCB_F_WRITE);
/* Notify readers to take the slow path. */
rcu_sync_enter(&sem->rss);
@@ -240,6 +241,7 @@ void __sched percpu_down_write(struct pe
/* Wait for all active readers to complete. */
rcuwait_wait_event(&sem->writer, readers_active_check(sem), TASK_UNINTERRUPTIBLE);
+ trace_contention_end(sem, 0);
}
EXPORT_SYMBOL_GPL(percpu_down_write);
--- a/kernel/locking/qrwlock.c
+++ b/kernel/locking/qrwlock.c
@@ -35,7 +35,7 @@ void queued_read_lock_slowpath(struct qr
}
atomic_sub(_QR_BIAS, &lock->cnts);
- trace_contention_begin(lock, LCB_F_READ | LCB_F_SPIN);
+ trace_contention_begin(lock, LCB_F_SPIN | LCB_F_READ);
/*
* Put the reader into the wait queue
@@ -67,7 +67,7 @@ void queued_write_lock_slowpath(struct q
{
int cnts;
- trace_contention_begin(lock, LCB_F_WRITE | LCB_F_SPIN);
+ trace_contention_begin(lock, LCB_F_SPIN | LCB_F_WRITE);
/* Put the writer into the wait queue */
arch_spin_lock(&lock->wait_lock);
--- a/kernel/locking/rwbase_rt.c
+++ b/kernel/locking/rwbase_rt.c
@@ -112,6 +112,8 @@ static int __sched __rwbase_read_lock(st
* Reader2 to call up_read(), which might be unbound.
*/
+ trace_contention_begin(rwb, LCB_F_RT | LCB_F_READ);
+
/*
* For rwlocks this returns 0 unconditionally, so the below
* !ret conditionals are optimized out.
@@ -130,6 +132,8 @@ static int __sched __rwbase_read_lock(st
raw_spin_unlock_irq(&rtm->wait_lock);
if (!ret)
rwbase_rtmutex_unlock(rtm);
+
+ trace_contention_end(rwb, ret);
return ret;
}
@@ -247,7 +251,7 @@ static int __sched rwbase_write_lock(str
goto out_unlock;
rwbase_set_and_save_current_state(state);
- trace_contention_begin(rwb, LCB_F_WRITE | LCB_F_RT);
+ trace_contention_begin(rwb, LCB_F_RT | LCB_F_WRITE);
for (;;) {
/* Optimized out for rwlocks */
if (rwbase_signal_pending_state(state, current)) {
