On Wed, Mar 16, 2022 at 03:45:48PM -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.
>
> 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 | 14 +++++++++++++-
> 8 files changed, 56 insertions(+), 1 deletion(-)
>
[...]
> diff --git a/kernel/locking/semaphore.c b/kernel/locking/semaphore.c
> index 9ee381e4d2a4..e3c19668dfee 100644
> --- a/kernel/locking/semaphore.c
> +++ b/kernel/locking/semaphore.c
> @@ -32,6 +32,7 @@
> #include <linux/semaphore.h>
> #include <linux/spinlock.h>
> #include <linux/ftrace.h>
> +#include <trace/events/lock.h>
>
> static noinline void __down(struct semaphore *sem);
> static noinline int __down_interruptible(struct semaphore *sem);
> @@ -209,6 +210,7 @@ static inline int __sched __down_common(struct semaphore *sem, long state,
> long timeout)
> {
> struct semaphore_waiter waiter;
> + bool tracing = false;
>
> list_add_tail(&waiter.list, &sem->wait_list);
> waiter.task = current;
> @@ -220,18 +222,28 @@ static inline int __sched __down_common(struct semaphore *sem, long state,
> if (unlikely(timeout <= 0))
> goto timed_out;
> __set_current_state(state);
> + if (!tracing) {
> + trace_contention_begin(sem, 0);
> + tracing = true;
> + }
> raw_spin_unlock_irq(&sem->lock);
> timeout = schedule_timeout(timeout);
> raw_spin_lock_irq(&sem->lock);
> - if (waiter.up)
> + if (waiter.up) {
> + trace_contention_end(sem, 0);
> return 0;
> + }
> }
>
> timed_out:
> + if (tracing)
> + trace_contention_end(sem, -ETIME);
> list_del(&waiter.list);
> return -ETIME;
>
> interrupted:
> + if (tracing)
> + trace_contention_end(sem, -EINTR);
> list_del(&waiter.list);
> return -EINTR;
> }
why not simply remove tracing variable and call trace_contention_begin()
earlier like in rwsem? we can ignore it if ret != 0.
--
Thank you, You are awesome!
Hyeonggon :-)
