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.
