Commit 1bece135 authored by Namhyung Kim's avatar Namhyung Kim Committed by Arnaldo Carvalho de Melo
Browse files

perf lock contention: Support old rw_semaphore type 



The old kernel has a different type of the owner field in rwsem.  We can
check it using bpf_core_type_matches() builtin in clang but it also
needs its own version check since it's available on recent versions.

Signed-off-by: default avatarNamhyung Kim <namhyung@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Hao Luo <haoluo@google.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Song Liu <song@kernel.org>
Cc: Waiman Long <longman@redhat.com>
Cc: Will Deacon <will@kernel.org>
Cc: bpf@vger.kernel.org
Link: https://lore.kernel.org/r/20230207002403.63590-4-namhyung@kernel.org


Signed-off-by: default avatarArnaldo Carvalho de Melo <acme@redhat.com>
parent 3477f079

tools/perf/util/bpf_skel/lock_contention.bpf.c

+44 −13
Original line number Diff line number Diff line
@@ -84,6 +84,14 @@ struct { 
	__uint(max_entries, 1);

} addr_filter SEC(".maps");



struct rw_semaphore___old {

	struct task_struct *owner;

} __attribute__((preserve_access_index));



struct rw_semaphore___new {

	atomic_long_t owner;

} __attribute__((preserve_access_index));



/* control flags */

int enabled;

int has_cpu;
@@ -161,6 +169,41 @@ static inline int update_task_data(struct task_struct *task) 
	return 0;

}



#ifndef __has_builtin

# define __has_builtin(x) 0

#endif



static inline struct task_struct *get_lock_owner(__u64 lock, __u32 flags)

{

	struct task_struct *task;

	__u64 owner = 0;



	if (flags & LCB_F_MUTEX) {

		struct mutex *mutex = (void *)lock;

		owner = BPF_CORE_READ(mutex, owner.counter);

	} else if (flags == LCB_F_READ || flags == LCB_F_WRITE) {

#if __has_builtin(bpf_core_type_matches)

		if (bpf_core_type_matches(struct rw_semaphore___old)) {

			struct rw_semaphore___old *rwsem = (void *)lock;

			owner = (unsigned long)BPF_CORE_READ(rwsem, owner);

		} else if (bpf_core_type_matches(struct rw_semaphore___new)) {

			struct rw_semaphore___new *rwsem = (void *)lock;

			owner = BPF_CORE_READ(rwsem, owner.counter);

		}

#else

		/* assume new struct */

		struct rw_semaphore *rwsem = (void *)lock;

		owner = BPF_CORE_READ(rwsem, owner.counter);

#endif

	}



	if (!owner)

		return NULL;



	task = (void *)(owner & ~7UL);

	return task;

}



SEC("tp_btf/contention_begin")

int contention_begin(u64 *ctx)

{
@@ -199,19 +242,7 @@ int contention_begin(u64 *ctx) 
		struct task_struct *task;



		if (lock_owner) {

			if (pelem->flags & LCB_F_MUTEX) {

				struct mutex *lock = (void *)pelem->lock;

				unsigned long owner = BPF_CORE_READ(lock, owner.counter);



				task = (void *)(owner & ~7UL);

			} else if (pelem->flags == LCB_F_READ || pelem->flags == LCB_F_WRITE) {

				struct rw_semaphore *lock = (void *)pelem->lock;

				unsigned long owner = BPF_CORE_READ(lock, owner.counter);



				task = (void *)(owner & ~7UL);

			} else {

				task = NULL;

			}

			task = get_lock_owner(pelem->lock, pelem->flags);



			/* The flags is not used anymore.  Pass the owner pid. */

			if (task)