On Tue, Mar 31, 2026 at 03:34:50AM -0700, Usama Arif wrote: > On Thu, 26 Mar 2026 15:10:02 +0000 Dmitry Ilvokhin <[email protected]> wrote: > > > Add the contended_release trace event. This tracepoint fires on the > > holder side when a contended lock is released, complementing the > > existing contention_begin/contention_end tracepoints which fire on the > > waiter side. > > > > This enables correlating lock hold time under contention with waiter > > events by lock address. > > > > Add trace_contended_release() calls to the slowpath unlock paths of > > sleepable locks: mutex, rtmutex, semaphore, rwsem, percpu-rwsem, and > > RT-specific rwbase locks. > > > > Where possible, trace_contended_release() fires before the lock is > > released and before the waiter is woken. For some lock types, the > > tracepoint fires after the release but before the wake. Making the > > placement consistent across all lock types is not worth the added > > complexity. > > > > For reader/writer locks, the tracepoint fires for every reader releasing > > while a writer is waiting, not only for the last reader. > > > > Signed-off-by: Dmitry Ilvokhin <[email protected]> > > --- > > include/trace/events/lock.h | 17 +++++++++++++++++ > > kernel/locking/mutex.c | 4 ++++ > > kernel/locking/percpu-rwsem.c | 11 +++++++++++ > > kernel/locking/rtmutex.c | 1 + > > kernel/locking/rwbase_rt.c | 6 ++++++ > > kernel/locking/rwsem.c | 10 ++++++++-- > > kernel/locking/semaphore.c | 4 ++++ > > 7 files changed, 51 insertions(+), 2 deletions(-) > > > > diff --git a/include/trace/events/lock.h b/include/trace/events/lock.h > > index da978f2afb45..1ded869cd619 100644 > > --- a/include/trace/events/lock.h > > +++ b/include/trace/events/lock.h > > @@ -137,6 +137,23 @@ TRACE_EVENT(contention_end, > > TP_printk("%p (ret=%d)", __entry->lock_addr, __entry->ret) > > ); > > > > +TRACE_EVENT(contended_release, > > + > > + TP_PROTO(void *lock), > > + > > + TP_ARGS(lock), > > + > > + TP_STRUCT__entry( > > + __field(void *, lock_addr) > > + ), > > + > > + TP_fast_assign( > > + __entry->lock_addr = lock; > > + ), > > + > > + TP_printk("%p", __entry->lock_addr) > > +); > > + > > #endif /* _TRACE_LOCK_H */ > > > > /* This part must be outside protection */ > > diff --git a/kernel/locking/mutex.c b/kernel/locking/mutex.c > > index 427187ff02db..6c2c9312eb8f 100644 > > --- a/kernel/locking/mutex.c > > +++ b/kernel/locking/mutex.c > > @@ -997,6 +997,9 @@ static noinline void __sched > > __mutex_unlock_slowpath(struct mutex *lock, unsigne > > wake_q_add(&wake_q, next); > > } > > > > + if (trace_contended_release_enabled() && waiter) > > + trace_contended_release(lock); > > + > > This won't compile? waiter is declared in the if block, so you are using > it outside scope here. >
Thanks for the feedback, Usama. waiter is declared at function scope, right on top. It's also assigned before the if block, so it's still in scope at the tracepoint.
