The existing contention_begin/contention_end tracepoints fire on the waiter side. The lock holder's identity and stack can be captured at contention_begin time (e.g. perf lock contention --lock-owner), but this reflects the holder's state when a waiter arrives, not when the lock is actually released.
This series adds a contended_release tracepoint that fires on the holder side when a lock with waiters is released. This provides: - Hold time estimation: when the holder's own acquisition was contended, its contention_end (acquisition) and contended_release can be correlated to measure how long the lock was held under contention. - The holder's stack at release time, which may differ from what perf lock contention --lock-owner captures if the holder does significant work between the waiter's arrival and the unlock. The tracepoint is placed exclusively in slowpath unlock paths, so there is no performance impact on the uncontended fast path and expected minimal impact on binary size. Dmitry Ilvokhin (3): locking: Add contended_release tracepoint locking/percpu-rwsem: Extract __percpu_up_read_slowpath() locking: Wire up contended_release tracepoint include/linux/percpu-rwsem.h | 15 +++------------ include/trace/events/lock.h | 17 +++++++++++++++++ kernel/locking/mutex.c | 1 + kernel/locking/percpu-rwsem.c | 21 +++++++++++++++++++++ kernel/locking/rtmutex.c | 1 + kernel/locking/rwbase_rt.c | 8 +++++++- kernel/locking/rwsem.c | 9 +++++++-- kernel/locking/semaphore.c | 4 +++- 8 files changed, 60 insertions(+), 16 deletions(-) -- 2.47.3
