This patch parses `owner_lock_stat` into a RB tree, enabling ordered
reporting of owner lock statistics with stack traces. It also updates
the documentation for the `-o` option in contention mode, decouples `-o`
from `-t`, and issues a warning to inform users about the new behavior
of `-ov`.
Example output:
$ sudo ~/linux/tools/perf/perf lock con -abvo -Y mutex-spin -E3 perf bench sched pipe
...
contended total wait max wait avg wait type caller
171 1.55 ms 20.26 us 9.06 us mutex pipe_read+0x57
0xffffffffac6318e7 pipe_read+0x57
0xffffffffac623862 vfs_read+0x332
0xffffffffac62434b ksys_read+0xbb
0xfffffffface604b2 do_syscall_64+0x82
0xffffffffad00012f entry_SYSCALL_64_after_hwframe+0x76
36 193.71 us 15.27 us 5.38 us mutex pipe_write+0x50
0xffffffffac631ee0 pipe_write+0x50
0xffffffffac6241db vfs_write+0x3bb
0xffffffffac6244ab ksys_write+0xbb
0xfffffffface604b2 do_syscall_64+0x82
0xffffffffad00012f entry_SYSCALL_64_after_hwframe+0x76
4 51.22 us 16.47 us 12.80 us mutex do_epoll_wait+0x24d
0xffffffffac691f0d do_epoll_wait+0x24d
0xffffffffac69249b do_epoll_pwait.part.0+0xb
0xffffffffac693ba5 __x64_sys_epoll_pwait+0x95
0xfffffffface604b2 do_syscall_64+0x82
0xffffffffad00012f entry_SYSCALL_64_after_hwframe+0x76
=== owner stack trace ===
3 31.24 us 15.27 us 10.41 us mutex pipe_read+0x348
0xffffffffac631bd8 pipe_read+0x348
0xffffffffac623862 vfs_read+0x332
0xffffffffac62434b ksys_read+0xbb
0xfffffffface604b2 do_syscall_64+0x82
0xffffffffad00012f entry_SYSCALL_64_after_hwframe+0x76
...
Signed-off-by: Chun-Tse Shao <ctshao@google.com>
---
tools/perf/Documentation/perf-lock.txt | 5 ++-
tools/perf/builtin-lock.c | 22 +++++++++-
tools/perf/util/bpf_lock_contention.c | 57 ++++++++++++++++++++++++++
tools/perf/util/lock-contention.h | 7 ++++
4 files changed, 87 insertions(+), 4 deletions(-)
diff --git a/tools/perf/Documentation/perf-lock.txt b/tools/perf/Documentation/perf-lock.txt
index d3793054f7d3..859dc11a7372 100644
--- a/tools/perf/Documentation/perf-lock.txt
+++ b/tools/perf/Documentation/perf-lock.txt
@@ -179,8 +179,9 @@ CONTENTION OPTIONS
-o::
--lock-owner::
- Show lock contention stat by owners. Implies --threads and
- requires --use-bpf.
+ Show lock contention stat by owners. This option can be combined with -t,
+ which shows owner's per thread lock stats, or -v, which shows owner's
+ stacktrace. Requires --use-bpf.
-Y::
--type-filter=<value>::
diff --git a/tools/perf/builtin-lock.c b/tools/perf/builtin-lock.c
index 9bebc186286f..05e7bc30488a 100644
--- a/tools/perf/builtin-lock.c
+++ b/tools/perf/builtin-lock.c
@@ -1817,6 +1817,22 @@ static void print_contention_result(struct lock_contention *con)
break;
}
+ if (con->owner && con->save_callstack && verbose > 0) {
+ struct rb_root root = RB_ROOT;
+
+ if (symbol_conf.field_sep)
+ fprintf(lock_output, "# owner stack trace:\n");
+ else
+ fprintf(lock_output, "\n=== owner stack trace ===\n\n");
+ while ((st = pop_owner_stack_trace(con)))
+ insert_to(&root, st, compare);
+
+ while ((st = pop_from(&root))) {
+ print_lock_stat(con, st);
+ free(st);
+ }
+ }
+
if (print_nr_entries) {
/* update the total/bad stats */
while ((st = pop_from_result())) {
@@ -1962,8 +1978,10 @@ static int check_lock_contention_options(const struct option *options,
}
}
- if (show_lock_owner)
- show_thread_stats = true;
+ if (show_lock_owner && !show_thread_stats) {
+ pr_warning("Now -o try to show owner's callstack instead of pid and comm.\n");
+ pr_warning("Please use -t option too to keep the old behavior.\n");
+ }
return 0;
}
diff --git a/tools/perf/util/bpf_lock_contention.c b/tools/perf/util/bpf_lock_contention.c
index 76542b86e83f..16f4deba69ec 100644
--- a/tools/perf/util/bpf_lock_contention.c
+++ b/tools/perf/util/bpf_lock_contention.c
@@ -549,6 +549,63 @@ static const char *lock_contention_get_name(struct lock_contention *con,
return name_buf;
}
+struct lock_stat *pop_owner_stack_trace(struct lock_contention *con)
+{
+ int stacks_fd, stat_fd;
+ u64 *stack_trace = NULL;
+ s32 stack_id;
+ struct contention_key ckey = {};
+ struct contention_data cdata = {};
+ size_t stack_size = con->max_stack * sizeof(*stack_trace);
+ struct lock_stat *st = NULL;
+
+ stacks_fd = bpf_map__fd(skel->maps.owner_stacks);
+ stat_fd = bpf_map__fd(skel->maps.owner_stat);
+ if (!stacks_fd || !stat_fd)
+ goto out_err;
+
+ stack_trace = zalloc(stack_size);
+ if (stack_trace == NULL)
+ goto out_err;
+
+ if (bpf_map_get_next_key(stacks_fd, NULL, stack_trace))
+ goto out_err;
+
+ bpf_map_lookup_elem(stacks_fd, stack_trace, &stack_id);
+ ckey.stack_id = stack_id;
+ bpf_map_lookup_elem(stat_fd, &ckey, &cdata);
+
+ st = zalloc(sizeof(struct lock_stat));
+ if (!st)
+ goto out_err;
+
+ st->name = strdup(stack_trace[0] ? lock_contention_get_name(con, NULL, stack_trace, 0) :
+ "unknown");
+ if (!st->name)
+ goto out_err;
+
+ st->flags = cdata.flags;
+ st->nr_contended = cdata.count;
+ st->wait_time_total = cdata.total_time;
+ st->wait_time_max = cdata.max_time;
+ st->wait_time_min = cdata.min_time;
+ st->callstack = stack_trace;
+
+ if (cdata.count)
+ st->avg_wait_time = cdata.total_time / cdata.count;
+
+ bpf_map_delete_elem(stacks_fd, stack_trace);
+ bpf_map_delete_elem(stat_fd, &ckey);
+
+ return st;
+
+out_err:
+ free(stack_trace);
+ free(st);
+
+ return NULL;
+}
+
int lock_contention_read(struct lock_contention *con)
{
int fd, stack, err = 0;
diff --git a/tools/perf/util/lock-contention.h b/tools/perf/util/lock-contention.h
index a09f7fe877df..97fd33c57f17 100644
--- a/tools/perf/util/lock-contention.h
+++ b/tools/perf/util/lock-contention.h
@@ -168,6 +168,8 @@ int lock_contention_stop(void);
int lock_contention_read(struct lock_contention *con);
int lock_contention_finish(struct lock_contention *con);
+struct lock_stat *pop_owner_stack_trace(struct lock_contention *con);
+
#else /* !HAVE_BPF_SKEL */
static inline int lock_contention_prepare(struct lock_contention *con __maybe_unused)
@@ -187,6 +189,11 @@ static inline int lock_contention_read(struct lock_contention *con __maybe_unuse
return 0;
}
+struct lock_stat *pop_owner_stack_trace(struct lock_contention *con)
+{
+ return NULL;
+}
+
#endif /* HAVE_BPF_SKEL */
#endif /* PERF_LOCK_CONTENTION_H */
--
2.48.1.658.g4767266eb4-goog
> On 25 Feb 2025, at 12:12 AM, Chun-Tse Shao <ctshao@google.com> wrote:
>
> This patch parses `owner_lock_stat` into a RB tree, enabling ordered
> reporting of owner lock statistics with stack traces. It also updates
> the documentation for the `-o` option in contention mode, decouples `-o`
> from `-t`, and issues a warning to inform users about the new behavior
> of `-ov`.
>
> Example output:
> $ sudo ~/linux/tools/perf/perf lock con -abvo -Y mutex-spin -E3 perf bench sched pipe
> ...
> contended total wait max wait avg wait type caller
>
> 171 1.55 ms 20.26 us 9.06 us mutex pipe_read+0x57
> 0xffffffffac6318e7 pipe_read+0x57
> 0xffffffffac623862 vfs_read+0x332
> 0xffffffffac62434b ksys_read+0xbb
> 0xfffffffface604b2 do_syscall_64+0x82
> 0xffffffffad00012f entry_SYSCALL_64_after_hwframe+0x76
> 36 193.71 us 15.27 us 5.38 us mutex pipe_write+0x50
> 0xffffffffac631ee0 pipe_write+0x50
> 0xffffffffac6241db vfs_write+0x3bb
> 0xffffffffac6244ab ksys_write+0xbb
> 0xfffffffface604b2 do_syscall_64+0x82
> 0xffffffffad00012f entry_SYSCALL_64_after_hwframe+0x76
> 4 51.22 us 16.47 us 12.80 us mutex do_epoll_wait+0x24d
> 0xffffffffac691f0d do_epoll_wait+0x24d
> 0xffffffffac69249b do_epoll_pwait.part.0+0xb
> 0xffffffffac693ba5 __x64_sys_epoll_pwait+0x95
> 0xfffffffface604b2 do_syscall_64+0x82
> 0xffffffffad00012f entry_SYSCALL_64_after_hwframe+0x76
>
> === owner stack trace ===
>
> 3 31.24 us 15.27 us 10.41 us mutex pipe_read+0x348
> 0xffffffffac631bd8 pipe_read+0x348
> 0xffffffffac623862 vfs_read+0x332
> 0xffffffffac62434b ksys_read+0xbb
> 0xfffffffface604b2 do_syscall_64+0x82
> 0xffffffffad00012f entry_SYSCALL_64_after_hwframe+0x76
> ...
>
> Signed-off-by: Chun-Tse Shao <ctshao@google.com>
> ---
> tools/perf/Documentation/perf-lock.txt | 5 ++-
> tools/perf/builtin-lock.c | 22 +++++++++-
> tools/perf/util/bpf_lock_contention.c | 57 ++++++++++++++++++++++++++
> tools/perf/util/lock-contention.h | 7 ++++
> 4 files changed, 87 insertions(+), 4 deletions(-)
>
> diff --git a/tools/perf/Documentation/perf-lock.txt b/tools/perf/Documentation/perf-lock.txt
> index d3793054f7d3..859dc11a7372 100644
> --- a/tools/perf/Documentation/perf-lock.txt
> +++ b/tools/perf/Documentation/perf-lock.txt
> @@ -179,8 +179,9 @@ CONTENTION OPTIONS
>
> -o::
> --lock-owner::
> - Show lock contention stat by owners. Implies --threads and
> - requires --use-bpf.
> + Show lock contention stat by owners. This option can be combined with -t,
> + which shows owner's per thread lock stats, or -v, which shows owner's
> + stacktrace. Requires --use-bpf.
>
> -Y::
> --type-filter=<value>::
> diff --git a/tools/perf/builtin-lock.c b/tools/perf/builtin-lock.c
> index 9bebc186286f..05e7bc30488a 100644
> --- a/tools/perf/builtin-lock.c
> +++ b/tools/perf/builtin-lock.c
> @@ -1817,6 +1817,22 @@ static void print_contention_result(struct lock_contention *con)
> break;
> }
>
> + if (con->owner && con->save_callstack && verbose > 0) {
> + struct rb_root root = RB_ROOT;
> +
> + if (symbol_conf.field_sep)
> + fprintf(lock_output, "# owner stack trace:\n");
> + else
> + fprintf(lock_output, "\n=== owner stack trace ===\n\n");
> + while ((st = pop_owner_stack_trace(con)))
> + insert_to(&root, st, compare);
> +
> + while ((st = pop_from(&root))) {
> + print_lock_stat(con, st);
> + free(st);
> + }
> + }
> +
> if (print_nr_entries) {
> /* update the total/bad stats */
> while ((st = pop_from_result())) {
> @@ -1962,8 +1978,10 @@ static int check_lock_contention_options(const struct option *options,
> }
> }
>
> - if (show_lock_owner)
> - show_thread_stats = true;
> + if (show_lock_owner && !show_thread_stats) {
> + pr_warning("Now -o try to show owner's callstack instead of pid and comm.\n");
> + pr_warning("Please use -t option too to keep the old behavior.\n");
> + }
>
> return 0;
> }
> diff --git a/tools/perf/util/bpf_lock_contention.c b/tools/perf/util/bpf_lock_contention.c
> index 76542b86e83f..16f4deba69ec 100644
> --- a/tools/perf/util/bpf_lock_contention.c
> +++ b/tools/perf/util/bpf_lock_contention.c
> @@ -549,6 +549,63 @@ static const char *lock_contention_get_name(struct lock_contention *con,
> return name_buf;
> }
>
> +struct lock_stat *pop_owner_stack_trace(struct lock_contention *con)
> +{
> + int stacks_fd, stat_fd;
> + u64 *stack_trace = NULL;
> + s32 stack_id;
> + struct contention_key ckey = {};
> + struct contention_data cdata = {};
> + size_t stack_size = con->max_stack * sizeof(*stack_trace);
> + struct lock_stat *st = NULL;
> +
> + stacks_fd = bpf_map__fd(skel->maps.owner_stacks);
> + stat_fd = bpf_map__fd(skel->maps.owner_stat);
> + if (!stacks_fd || !stat_fd)
> + goto out_err;
> +
> + stack_trace = zalloc(stack_size);
> + if (stack_trace == NULL)
> + goto out_err;
> +
> + if (bpf_map_get_next_key(stacks_fd, NULL, stack_trace))
> + goto out_err;
> +
> + bpf_map_lookup_elem(stacks_fd, stack_trace, &stack_id);
> + ckey.stack_id = stack_id;
> + bpf_map_lookup_elem(stat_fd, &ckey, &cdata);
> +
> + st = zalloc(sizeof(struct lock_stat));
> + if (!st)
> + goto out_err;
> +
> + st->name = strdup(stack_trace[0] ? lock_contention_get_name(con, NULL, stack_trace, 0) :
> + "unknown");
Hi,
I am hitting a compilation issue with this change. Sorry for responding late. I tried with change from tmp.perf-tools-next and hit below issue:
CC util/bpf_lock_contention.o
util/bpf_lock_contention.c: In function ‘lock_contention_get_name’:
cc1: error: function may return address of local variable [-Werror=return-local-addr]
util/bpf_lock_contention.c:470:45: note: declared here
470 | struct contention_task_data task;
| ^~~~
cc1: all warnings being treated as errors
make[4]: *** [/root/perf-tools-next/tools/build/Makefile.build:85: util/bpf_lock_contention.o] Error 1
make[4]: *** Waiting for unfinished jobs....
LD perf-in.o
make[3]: *** [/root/perf-tools-next/tools/build/Makefile.build:138: util] Error 2
make[2]: *** [Makefile.perf:822: perf-util-in.o] Error 2
make[1]: *** [Makefile.perf:321: sub-make] Error 2
make: *** [Makefile:76: all] Error 2
Code snippet:
if (con->aggr_mode == LOCK_AGGR_TASK) {
struct contention_task_data task;
int pid = key->pid;
int task_fd = bpf_map__fd(skel->maps.task_data);
/* do not update idle comm which contains CPU number */
if (pid) {
struct thread *t = machine__findnew_thread(machine, /*pid=*/-1, pid);
if (t == NULL)
return name;
if (!bpf_map_lookup_elem(task_fd, &pid, &task) &&
thread__set_comm(t, task.comm, /*timestamp=*/0))
name = task.comm;
}
return name;
}
We are calling lock_contention_get_name with second argument as NULL .
Though error above points to “contention_task_data”, I think the local variable here is for “name” ?
Thanks
Athira
> + if (!st->name)
> + goto out_err;
> +
> + st->flags = cdata.flags;
> + st->nr_contended = cdata.count;
> + st->wait_time_total = cdata.total_time;
> + st->wait_time_max = cdata.max_time;
> + st->wait_time_min = cdata.min_time;
> + st->callstack = stack_trace;
> +
> + if (cdata.count)
> + st->avg_wait_time = cdata.total_time / cdata.count;
> +
> + bpf_map_delete_elem(stacks_fd, stack_trace);
> + bpf_map_delete_elem(stat_fd, &ckey);
> +
> + return st;
> +
> +out_err:
> + free(stack_trace);
> + free(st);
> +
> + return NULL;
> +}
> +
> int lock_contention_read(struct lock_contention *con)
> {
> int fd, stack, err = 0;
> diff --git a/tools/perf/util/lock-contention.h b/tools/perf/util/lock-contention.h
> index a09f7fe877df..97fd33c57f17 100644
> --- a/tools/perf/util/lock-contention.h
> +++ b/tools/perf/util/lock-contention.h
> @@ -168,6 +168,8 @@ int lock_contention_stop(void);
> int lock_contention_read(struct lock_contention *con);
> int lock_contention_finish(struct lock_contention *con);
>
> +struct lock_stat *pop_owner_stack_trace(struct lock_contention *con);
> +
> #else /* !HAVE_BPF_SKEL */
>
> static inline int lock_contention_prepare(struct lock_contention *con __maybe_unused)
> @@ -187,6 +189,11 @@ static inline int lock_contention_read(struct lock_contention *con __maybe_unuse
> return 0;
> }
>
> +struct lock_stat *pop_owner_stack_trace(struct lock_contention *con)
> +{
> + return NULL;
> +}
> +
> #endif /* HAVE_BPF_SKEL */
>
> #endif /* PERF_LOCK_CONTENTION_H */
> --
> 2.48.1.658.g4767266eb4-goog
>
>
Hello,
On Wed, Feb 26, 2025 at 03:27:41PM +0530, Athira Rajeev wrote:
>
>
> > On 25 Feb 2025, at 12:12 AM, Chun-Tse Shao <ctshao@google.com> wrote:
> >
> > This patch parses `owner_lock_stat` into a RB tree, enabling ordered
> > reporting of owner lock statistics with stack traces. It also updates
> > the documentation for the `-o` option in contention mode, decouples `-o`
> > from `-t`, and issues a warning to inform users about the new behavior
> > of `-ov`.
> >
> > Example output:
> > $ sudo ~/linux/tools/perf/perf lock con -abvo -Y mutex-spin -E3 perf bench sched pipe
> > ...
> > contended total wait max wait avg wait type caller
> >
> > 171 1.55 ms 20.26 us 9.06 us mutex pipe_read+0x57
> > 0xffffffffac6318e7 pipe_read+0x57
> > 0xffffffffac623862 vfs_read+0x332
> > 0xffffffffac62434b ksys_read+0xbb
> > 0xfffffffface604b2 do_syscall_64+0x82
> > 0xffffffffad00012f entry_SYSCALL_64_after_hwframe+0x76
> > 36 193.71 us 15.27 us 5.38 us mutex pipe_write+0x50
> > 0xffffffffac631ee0 pipe_write+0x50
> > 0xffffffffac6241db vfs_write+0x3bb
> > 0xffffffffac6244ab ksys_write+0xbb
> > 0xfffffffface604b2 do_syscall_64+0x82
> > 0xffffffffad00012f entry_SYSCALL_64_after_hwframe+0x76
> > 4 51.22 us 16.47 us 12.80 us mutex do_epoll_wait+0x24d
> > 0xffffffffac691f0d do_epoll_wait+0x24d
> > 0xffffffffac69249b do_epoll_pwait.part.0+0xb
> > 0xffffffffac693ba5 __x64_sys_epoll_pwait+0x95
> > 0xfffffffface604b2 do_syscall_64+0x82
> > 0xffffffffad00012f entry_SYSCALL_64_after_hwframe+0x76
> >
> > === owner stack trace ===
> >
> > 3 31.24 us 15.27 us 10.41 us mutex pipe_read+0x348
> > 0xffffffffac631bd8 pipe_read+0x348
> > 0xffffffffac623862 vfs_read+0x332
> > 0xffffffffac62434b ksys_read+0xbb
> > 0xfffffffface604b2 do_syscall_64+0x82
> > 0xffffffffad00012f entry_SYSCALL_64_after_hwframe+0x76
> > ...
> >
> > Signed-off-by: Chun-Tse Shao <ctshao@google.com>
> > ---
> > tools/perf/Documentation/perf-lock.txt | 5 ++-
> > tools/perf/builtin-lock.c | 22 +++++++++-
> > tools/perf/util/bpf_lock_contention.c | 57 ++++++++++++++++++++++++++
> > tools/perf/util/lock-contention.h | 7 ++++
> > 4 files changed, 87 insertions(+), 4 deletions(-)
> >
> > diff --git a/tools/perf/Documentation/perf-lock.txt b/tools/perf/Documentation/perf-lock.txt
> > index d3793054f7d3..859dc11a7372 100644
> > --- a/tools/perf/Documentation/perf-lock.txt
> > +++ b/tools/perf/Documentation/perf-lock.txt
> > @@ -179,8 +179,9 @@ CONTENTION OPTIONS
> >
> > -o::
> > --lock-owner::
> > - Show lock contention stat by owners. Implies --threads and
> > - requires --use-bpf.
> > + Show lock contention stat by owners. This option can be combined with -t,
> > + which shows owner's per thread lock stats, or -v, which shows owner's
> > + stacktrace. Requires --use-bpf.
> >
> > -Y::
> > --type-filter=<value>::
> > diff --git a/tools/perf/builtin-lock.c b/tools/perf/builtin-lock.c
> > index 9bebc186286f..05e7bc30488a 100644
> > --- a/tools/perf/builtin-lock.c
> > +++ b/tools/perf/builtin-lock.c
> > @@ -1817,6 +1817,22 @@ static void print_contention_result(struct lock_contention *con)
> > break;
> > }
> >
> > + if (con->owner && con->save_callstack && verbose > 0) {
> > + struct rb_root root = RB_ROOT;
> > +
> > + if (symbol_conf.field_sep)
> > + fprintf(lock_output, "# owner stack trace:\n");
> > + else
> > + fprintf(lock_output, "\n=== owner stack trace ===\n\n");
> > + while ((st = pop_owner_stack_trace(con)))
> > + insert_to(&root, st, compare);
> > +
> > + while ((st = pop_from(&root))) {
> > + print_lock_stat(con, st);
> > + free(st);
> > + }
> > + }
> > +
> > if (print_nr_entries) {
> > /* update the total/bad stats */
> > while ((st = pop_from_result())) {
> > @@ -1962,8 +1978,10 @@ static int check_lock_contention_options(const struct option *options,
> > }
> > }
> >
> > - if (show_lock_owner)
> > - show_thread_stats = true;
> > + if (show_lock_owner && !show_thread_stats) {
> > + pr_warning("Now -o try to show owner's callstack instead of pid and comm.\n");
> > + pr_warning("Please use -t option too to keep the old behavior.\n");
> > + }
> >
> > return 0;
> > }
> > diff --git a/tools/perf/util/bpf_lock_contention.c b/tools/perf/util/bpf_lock_contention.c
> > index 76542b86e83f..16f4deba69ec 100644
> > --- a/tools/perf/util/bpf_lock_contention.c
> > +++ b/tools/perf/util/bpf_lock_contention.c
> > @@ -549,6 +549,63 @@ static const char *lock_contention_get_name(struct lock_contention *con,
> > return name_buf;
> > }
> >
> > +struct lock_stat *pop_owner_stack_trace(struct lock_contention *con)
> > +{
> > + int stacks_fd, stat_fd;
> > + u64 *stack_trace = NULL;
> > + s32 stack_id;
> > + struct contention_key ckey = {};
> > + struct contention_data cdata = {};
> > + size_t stack_size = con->max_stack * sizeof(*stack_trace);
> > + struct lock_stat *st = NULL;
> > +
> > + stacks_fd = bpf_map__fd(skel->maps.owner_stacks);
> > + stat_fd = bpf_map__fd(skel->maps.owner_stat);
> > + if (!stacks_fd || !stat_fd)
> > + goto out_err;
> > +
> > + stack_trace = zalloc(stack_size);
> > + if (stack_trace == NULL)
> > + goto out_err;
> > +
> > + if (bpf_map_get_next_key(stacks_fd, NULL, stack_trace))
> > + goto out_err;
> > +
> > + bpf_map_lookup_elem(stacks_fd, stack_trace, &stack_id);
> > + ckey.stack_id = stack_id;
> > + bpf_map_lookup_elem(stat_fd, &ckey, &cdata);
> > +
> > + st = zalloc(sizeof(struct lock_stat));
> > + if (!st)
> > + goto out_err;
> > +
> > + st->name = strdup(stack_trace[0] ? lock_contention_get_name(con, NULL, stack_trace, 0) :
> > + "unknown");
>
> Hi,
>
> I am hitting a compilation issue with this change. Sorry for responding late. I tried with change from tmp.perf-tools-next and hit below issue:
>
>
> CC util/bpf_lock_contention.o
> util/bpf_lock_contention.c: In function ‘lock_contention_get_name’:
> cc1: error: function may return address of local variable [-Werror=return-local-addr]
> util/bpf_lock_contention.c:470:45: note: declared here
> 470 | struct contention_task_data task;
> | ^~~~
> cc1: all warnings being treated as errors
> make[4]: *** [/root/perf-tools-next/tools/build/Makefile.build:85: util/bpf_lock_contention.o] Error 1
> make[4]: *** Waiting for unfinished jobs....
> LD perf-in.o
> make[3]: *** [/root/perf-tools-next/tools/build/Makefile.build:138: util] Error 2
> make[2]: *** [Makefile.perf:822: perf-util-in.o] Error 2
> make[1]: *** [Makefile.perf:321: sub-make] Error 2
> make: *** [Makefile:76: all] Error 2
Thanks for the report. I've noticed that and also found this error:
In file included from util/lock-contention.c:4:0:
util/lock-contention.h:192:19: error: no previous prototype for 'pop_owner_stack_trace' [-Werror=missing-prototypes]
struct lock_stat *pop_owner_stack_trace(struct lock_contention *con)
^~~~~~~~~~~~~~~~~~~~~
util/lock-contention.h: In function 'pop_owner_stack_trace':
util/lock-contention.h:192:65: error: unused parameter 'con' [-Werror=unused-parameter]
struct lock_stat *pop_owner_stack_trace(struct lock_contention *con)
^~~
Removed this series from tmp.perf-tools-next.
Thanks,
Namhyung
>
>
> Code snippet:
>
> if (con->aggr_mode == LOCK_AGGR_TASK) {
> struct contention_task_data task;
> int pid = key->pid;
> int task_fd = bpf_map__fd(skel->maps.task_data);
>
> /* do not update idle comm which contains CPU number */
> if (pid) {
> struct thread *t = machine__findnew_thread(machine, /*pid=*/-1, pid);
>
> if (t == NULL)
> return name;
> if (!bpf_map_lookup_elem(task_fd, &pid, &task) &&
> thread__set_comm(t, task.comm, /*timestamp=*/0))
> name = task.comm;
> }
> return name;
> }
>
>
> We are calling lock_contention_get_name with second argument as NULL .
> Though error above points to “contention_task_data”, I think the local variable here is for “name” ?
>
>
> Thanks
> Athira
>
> > + if (!st->name)
> > + goto out_err;
> > +
> > + st->flags = cdata.flags;
> > + st->nr_contended = cdata.count;
> > + st->wait_time_total = cdata.total_time;
> > + st->wait_time_max = cdata.max_time;
> > + st->wait_time_min = cdata.min_time;
> > + st->callstack = stack_trace;
> > +
> > + if (cdata.count)
> > + st->avg_wait_time = cdata.total_time / cdata.count;
> > +
> > + bpf_map_delete_elem(stacks_fd, stack_trace);
> > + bpf_map_delete_elem(stat_fd, &ckey);
> > +
> > + return st;
> > +
> > +out_err:
> > + free(stack_trace);
> > + free(st);
> > +
> > + return NULL;
> > +}
> > +
> > int lock_contention_read(struct lock_contention *con)
> > {
> > int fd, stack, err = 0;
> > diff --git a/tools/perf/util/lock-contention.h b/tools/perf/util/lock-contention.h
> > index a09f7fe877df..97fd33c57f17 100644
> > --- a/tools/perf/util/lock-contention.h
> > +++ b/tools/perf/util/lock-contention.h
> > @@ -168,6 +168,8 @@ int lock_contention_stop(void);
> > int lock_contention_read(struct lock_contention *con);
> > int lock_contention_finish(struct lock_contention *con);
> >
> > +struct lock_stat *pop_owner_stack_trace(struct lock_contention *con);
> > +
> > #else /* !HAVE_BPF_SKEL */
> >
> > static inline int lock_contention_prepare(struct lock_contention *con __maybe_unused)
> > @@ -187,6 +189,11 @@ static inline int lock_contention_read(struct lock_contention *con __maybe_unuse
> > return 0;
> > }
> >
> > +struct lock_stat *pop_owner_stack_trace(struct lock_contention *con)
> > +{
> > + return NULL;
> > +}
> > +
> > #endif /* HAVE_BPF_SKEL */
> >
> > #endif /* PERF_LOCK_CONTENTION_H */
> > --
> > 2.48.1.658.g4767266eb4-goog
> >
> >
>
Hi Namhyung and Athira, thanks for your investigation! I fixed them
and submitted v8:
https://lore.kernel.org/20250227003359.732948-1-ctshao@google.com/
For `lock_contention_get_name `, I am not sure why the error is
revealed by me since I did not touch that part of code. Anyway I also
included the fix in my patchset.
Thank you,
CT
On Wed, Feb 26, 2025 at 9:42 AM Namhyung Kim <namhyung@kernel.org> wrote:
>
> Hello,
>
> On Wed, Feb 26, 2025 at 03:27:41PM +0530, Athira Rajeev wrote:
> >
> >
> > > On 25 Feb 2025, at 12:12 AM, Chun-Tse Shao <ctshao@google.com> wrote:
> > >
> > > This patch parses `owner_lock_stat` into a RB tree, enabling ordered
> > > reporting of owner lock statistics with stack traces. It also updates
> > > the documentation for the `-o` option in contention mode, decouples `-o`
> > > from `-t`, and issues a warning to inform users about the new behavior
> > > of `-ov`.
> > >
> > > Example output:
> > > $ sudo ~/linux/tools/perf/perf lock con -abvo -Y mutex-spin -E3 perf bench sched pipe
> > > ...
> > > contended total wait max wait avg wait type caller
> > >
> > > 171 1.55 ms 20.26 us 9.06 us mutex pipe_read+0x57
> > > 0xffffffffac6318e7 pipe_read+0x57
> > > 0xffffffffac623862 vfs_read+0x332
> > > 0xffffffffac62434b ksys_read+0xbb
> > > 0xfffffffface604b2 do_syscall_64+0x82
> > > 0xffffffffad00012f entry_SYSCALL_64_after_hwframe+0x76
> > > 36 193.71 us 15.27 us 5.38 us mutex pipe_write+0x50
> > > 0xffffffffac631ee0 pipe_write+0x50
> > > 0xffffffffac6241db vfs_write+0x3bb
> > > 0xffffffffac6244ab ksys_write+0xbb
> > > 0xfffffffface604b2 do_syscall_64+0x82
> > > 0xffffffffad00012f entry_SYSCALL_64_after_hwframe+0x76
> > > 4 51.22 us 16.47 us 12.80 us mutex do_epoll_wait+0x24d
> > > 0xffffffffac691f0d do_epoll_wait+0x24d
> > > 0xffffffffac69249b do_epoll_pwait.part.0+0xb
> > > 0xffffffffac693ba5 __x64_sys_epoll_pwait+0x95
> > > 0xfffffffface604b2 do_syscall_64+0x82
> > > 0xffffffffad00012f entry_SYSCALL_64_after_hwframe+0x76
> > >
> > > === owner stack trace ===
> > >
> > > 3 31.24 us 15.27 us 10.41 us mutex pipe_read+0x348
> > > 0xffffffffac631bd8 pipe_read+0x348
> > > 0xffffffffac623862 vfs_read+0x332
> > > 0xffffffffac62434b ksys_read+0xbb
> > > 0xfffffffface604b2 do_syscall_64+0x82
> > > 0xffffffffad00012f entry_SYSCALL_64_after_hwframe+0x76
> > > ...
> > >
> > > Signed-off-by: Chun-Tse Shao <ctshao@google.com>
> > > ---
> > > tools/perf/Documentation/perf-lock.txt | 5 ++-
> > > tools/perf/builtin-lock.c | 22 +++++++++-
> > > tools/perf/util/bpf_lock_contention.c | 57 ++++++++++++++++++++++++++
> > > tools/perf/util/lock-contention.h | 7 ++++
> > > 4 files changed, 87 insertions(+), 4 deletions(-)
> > >
> > > diff --git a/tools/perf/Documentation/perf-lock.txt b/tools/perf/Documentation/perf-lock.txt
> > > index d3793054f7d3..859dc11a7372 100644
> > > --- a/tools/perf/Documentation/perf-lock.txt
> > > +++ b/tools/perf/Documentation/perf-lock.txt
> > > @@ -179,8 +179,9 @@ CONTENTION OPTIONS
> > >
> > > -o::
> > > --lock-owner::
> > > - Show lock contention stat by owners. Implies --threads and
> > > - requires --use-bpf.
> > > + Show lock contention stat by owners. This option can be combined with -t,
> > > + which shows owner's per thread lock stats, or -v, which shows owner's
> > > + stacktrace. Requires --use-bpf.
> > >
> > > -Y::
> > > --type-filter=<value>::
> > > diff --git a/tools/perf/builtin-lock.c b/tools/perf/builtin-lock.c
> > > index 9bebc186286f..05e7bc30488a 100644
> > > --- a/tools/perf/builtin-lock.c
> > > +++ b/tools/perf/builtin-lock.c
> > > @@ -1817,6 +1817,22 @@ static void print_contention_result(struct lock_contention *con)
> > > break;
> > > }
> > >
> > > + if (con->owner && con->save_callstack && verbose > 0) {
> > > + struct rb_root root = RB_ROOT;
> > > +
> > > + if (symbol_conf.field_sep)
> > > + fprintf(lock_output, "# owner stack trace:\n");
> > > + else
> > > + fprintf(lock_output, "\n=== owner stack trace ===\n\n");
> > > + while ((st = pop_owner_stack_trace(con)))
> > > + insert_to(&root, st, compare);
> > > +
> > > + while ((st = pop_from(&root))) {
> > > + print_lock_stat(con, st);
> > > + free(st);
> > > + }
> > > + }
> > > +
> > > if (print_nr_entries) {
> > > /* update the total/bad stats */
> > > while ((st = pop_from_result())) {
> > > @@ -1962,8 +1978,10 @@ static int check_lock_contention_options(const struct option *options,
> > > }
> > > }
> > >
> > > - if (show_lock_owner)
> > > - show_thread_stats = true;
> > > + if (show_lock_owner && !show_thread_stats) {
> > > + pr_warning("Now -o try to show owner's callstack instead of pid and comm.\n");
> > > + pr_warning("Please use -t option too to keep the old behavior.\n");
> > > + }
> > >
> > > return 0;
> > > }
> > > diff --git a/tools/perf/util/bpf_lock_contention.c b/tools/perf/util/bpf_lock_contention.c
> > > index 76542b86e83f..16f4deba69ec 100644
> > > --- a/tools/perf/util/bpf_lock_contention.c
> > > +++ b/tools/perf/util/bpf_lock_contention.c
> > > @@ -549,6 +549,63 @@ static const char *lock_contention_get_name(struct lock_contention *con,
> > > return name_buf;
> > > }
> > >
> > > +struct lock_stat *pop_owner_stack_trace(struct lock_contention *con)
> > > +{
> > > + int stacks_fd, stat_fd;
> > > + u64 *stack_trace = NULL;
> > > + s32 stack_id;
> > > + struct contention_key ckey = {};
> > > + struct contention_data cdata = {};
> > > + size_t stack_size = con->max_stack * sizeof(*stack_trace);
> > > + struct lock_stat *st = NULL;
> > > +
> > > + stacks_fd = bpf_map__fd(skel->maps.owner_stacks);
> > > + stat_fd = bpf_map__fd(skel->maps.owner_stat);
> > > + if (!stacks_fd || !stat_fd)
> > > + goto out_err;
> > > +
> > > + stack_trace = zalloc(stack_size);
> > > + if (stack_trace == NULL)
> > > + goto out_err;
> > > +
> > > + if (bpf_map_get_next_key(stacks_fd, NULL, stack_trace))
> > > + goto out_err;
> > > +
> > > + bpf_map_lookup_elem(stacks_fd, stack_trace, &stack_id);
> > > + ckey.stack_id = stack_id;
> > > + bpf_map_lookup_elem(stat_fd, &ckey, &cdata);
> > > +
> > > + st = zalloc(sizeof(struct lock_stat));
> > > + if (!st)
> > > + goto out_err;
> > > +
> > > + st->name = strdup(stack_trace[0] ? lock_contention_get_name(con, NULL, stack_trace, 0) :
> > > + "unknown");
> >
> > Hi,
> >
> > I am hitting a compilation issue with this change. Sorry for responding late. I tried with change from tmp.perf-tools-next and hit below issue:
> >
> >
> > CC util/bpf_lock_contention.o
> > util/bpf_lock_contention.c: In function ‘lock_contention_get_name’:
> > cc1: error: function may return address of local variable [-Werror=return-local-addr]
> > util/bpf_lock_contention.c:470:45: note: declared here
> > 470 | struct contention_task_data task;
> > | ^~~~
> > cc1: all warnings being treated as errors
> > make[4]: *** [/root/perf-tools-next/tools/build/Makefile.build:85: util/bpf_lock_contention.o] Error 1
> > make[4]: *** Waiting for unfinished jobs....
> > LD perf-in.o
> > make[3]: *** [/root/perf-tools-next/tools/build/Makefile.build:138: util] Error 2
> > make[2]: *** [Makefile.perf:822: perf-util-in.o] Error 2
> > make[1]: *** [Makefile.perf:321: sub-make] Error 2
> > make: *** [Makefile:76: all] Error 2
>
> Thanks for the report. I've noticed that and also found this error:
>
> In file included from util/lock-contention.c:4:0:
> util/lock-contention.h:192:19: error: no previous prototype for 'pop_owner_stack_trace' [-Werror=missing-prototypes]
> struct lock_stat *pop_owner_stack_trace(struct lock_contention *con)
> ^~~~~~~~~~~~~~~~~~~~~
> util/lock-contention.h: In function 'pop_owner_stack_trace':
> util/lock-contention.h:192:65: error: unused parameter 'con' [-Werror=unused-parameter]
> struct lock_stat *pop_owner_stack_trace(struct lock_contention *con)
> ^~~
>
> Removed this series from tmp.perf-tools-next.
>
> Thanks,
> Namhyung
>
> >
> >
> > Code snippet:
> >
> > if (con->aggr_mode == LOCK_AGGR_TASK) {
> > struct contention_task_data task;
> > int pid = key->pid;
> > int task_fd = bpf_map__fd(skel->maps.task_data);
> >
> > /* do not update idle comm which contains CPU number */
> > if (pid) {
> > struct thread *t = machine__findnew_thread(machine, /*pid=*/-1, pid);
> >
> > if (t == NULL)
> > return name;
> > if (!bpf_map_lookup_elem(task_fd, &pid, &task) &&
> > thread__set_comm(t, task.comm, /*timestamp=*/0))
> > name = task.comm;
> > }
> > return name;
> > }
> >
> >
> > We are calling lock_contention_get_name with second argument as NULL .
> > Though error above points to “contention_task_data”, I think the local variable here is for “name” ?
> >
> >
> > Thanks
> > Athira
> >
> > > + if (!st->name)
> > > + goto out_err;
> > > +
> > > + st->flags = cdata.flags;
> > > + st->nr_contended = cdata.count;
> > > + st->wait_time_total = cdata.total_time;
> > > + st->wait_time_max = cdata.max_time;
> > > + st->wait_time_min = cdata.min_time;
> > > + st->callstack = stack_trace;
> > > +
> > > + if (cdata.count)
> > > + st->avg_wait_time = cdata.total_time / cdata.count;
> > > +
> > > + bpf_map_delete_elem(stacks_fd, stack_trace);
> > > + bpf_map_delete_elem(stat_fd, &ckey);
> > > +
> > > + return st;
> > > +
> > > +out_err:
> > > + free(stack_trace);
> > > + free(st);
> > > +
> > > + return NULL;
> > > +}
> > > +
> > > int lock_contention_read(struct lock_contention *con)
> > > {
> > > int fd, stack, err = 0;
> > > diff --git a/tools/perf/util/lock-contention.h b/tools/perf/util/lock-contention.h
> > > index a09f7fe877df..97fd33c57f17 100644
> > > --- a/tools/perf/util/lock-contention.h
> > > +++ b/tools/perf/util/lock-contention.h
> > > @@ -168,6 +168,8 @@ int lock_contention_stop(void);
> > > int lock_contention_read(struct lock_contention *con);
> > > int lock_contention_finish(struct lock_contention *con);
> > >
> > > +struct lock_stat *pop_owner_stack_trace(struct lock_contention *con);
> > > +
> > > #else /* !HAVE_BPF_SKEL */
> > >
> > > static inline int lock_contention_prepare(struct lock_contention *con __maybe_unused)
> > > @@ -187,6 +189,11 @@ static inline int lock_contention_read(struct lock_contention *con __maybe_unuse
> > > return 0;
> > > }
> > >
> > > +struct lock_stat *pop_owner_stack_trace(struct lock_contention *con)
> > > +{
> > > + return NULL;
> > > +}
> > > +
> > > #endif /* HAVE_BPF_SKEL */
> > >
> > > #endif /* PERF_LOCK_CONTENTION_H */
> > > --
> > > 2.48.1.658.g4767266eb4-goog
> > >
> > >
> >
> On 27 Feb 2025, at 6:05 AM, Chun-Tse Shao <ctshao@google.com> wrote:
>
> Hi Namhyung and Athira, thanks for your investigation! I fixed them
> and submitted v8:
> https://lore.kernel.org/20250227003359.732948-1-ctshao@google.com/
>
> For `lock_contention_get_name `, I am not sure why the error is
> revealed by me since I did not touch that part of code. Anyway I also
> included the fix in my patchset.
>
> Thank you,
> CT
Hi Chun-Tse,
Sure, I will compile test with the version 8 and respond to the v8 mail thread.
Thanks
Athira
>
>
>
> On Wed, Feb 26, 2025 at 9:42 AM Namhyung Kim <namhyung@kernel.org> wrote:
>>
>> Hello,
>>
>> On Wed, Feb 26, 2025 at 03:27:41PM +0530, Athira Rajeev wrote:
>>>
>>>
>>>> On 25 Feb 2025, at 12:12 AM, Chun-Tse Shao <ctshao@google.com> wrote:
>>>>
>>>> This patch parses `owner_lock_stat` into a RB tree, enabling ordered
>>>> reporting of owner lock statistics with stack traces. It also updates
>>>> the documentation for the `-o` option in contention mode, decouples `-o`
>>>> from `-t`, and issues a warning to inform users about the new behavior
>>>> of `-ov`.
>>>>
>>>> Example output:
>>>> $ sudo ~/linux/tools/perf/perf lock con -abvo -Y mutex-spin -E3 perf bench sched pipe
>>>> ...
>>>> contended total wait max wait avg wait type caller
>>>>
>>>> 171 1.55 ms 20.26 us 9.06 us mutex pipe_read+0x57
>>>> 0xffffffffac6318e7 pipe_read+0x57
>>>> 0xffffffffac623862 vfs_read+0x332
>>>> 0xffffffffac62434b ksys_read+0xbb
>>>> 0xfffffffface604b2 do_syscall_64+0x82
>>>> 0xffffffffad00012f entry_SYSCALL_64_after_hwframe+0x76
>>>> 36 193.71 us 15.27 us 5.38 us mutex pipe_write+0x50
>>>> 0xffffffffac631ee0 pipe_write+0x50
>>>> 0xffffffffac6241db vfs_write+0x3bb
>>>> 0xffffffffac6244ab ksys_write+0xbb
>>>> 0xfffffffface604b2 do_syscall_64+0x82
>>>> 0xffffffffad00012f entry_SYSCALL_64_after_hwframe+0x76
>>>> 4 51.22 us 16.47 us 12.80 us mutex do_epoll_wait+0x24d
>>>> 0xffffffffac691f0d do_epoll_wait+0x24d
>>>> 0xffffffffac69249b do_epoll_pwait.part.0+0xb
>>>> 0xffffffffac693ba5 __x64_sys_epoll_pwait+0x95
>>>> 0xfffffffface604b2 do_syscall_64+0x82
>>>> 0xffffffffad00012f entry_SYSCALL_64_after_hwframe+0x76
>>>>
>>>> === owner stack trace ===
>>>>
>>>> 3 31.24 us 15.27 us 10.41 us mutex pipe_read+0x348
>>>> 0xffffffffac631bd8 pipe_read+0x348
>>>> 0xffffffffac623862 vfs_read+0x332
>>>> 0xffffffffac62434b ksys_read+0xbb
>>>> 0xfffffffface604b2 do_syscall_64+0x82
>>>> 0xffffffffad00012f entry_SYSCALL_64_after_hwframe+0x76
>>>> ...
>>>>
>>>> Signed-off-by: Chun-Tse Shao <ctshao@google.com>
>>>> ---
>>>> tools/perf/Documentation/perf-lock.txt | 5 ++-
>>>> tools/perf/builtin-lock.c | 22 +++++++++-
>>>> tools/perf/util/bpf_lock_contention.c | 57 ++++++++++++++++++++++++++
>>>> tools/perf/util/lock-contention.h | 7 ++++
>>>> 4 files changed, 87 insertions(+), 4 deletions(-)
>>>>
>>>> diff --git a/tools/perf/Documentation/perf-lock.txt b/tools/perf/Documentation/perf-lock.txt
>>>> index d3793054f7d3..859dc11a7372 100644
>>>> --- a/tools/perf/Documentation/perf-lock.txt
>>>> +++ b/tools/perf/Documentation/perf-lock.txt
>>>> @@ -179,8 +179,9 @@ CONTENTION OPTIONS
>>>>
>>>> -o::
>>>> --lock-owner::
>>>> - Show lock contention stat by owners. Implies --threads and
>>>> - requires --use-bpf.
>>>> + Show lock contention stat by owners. This option can be combined with -t,
>>>> + which shows owner's per thread lock stats, or -v, which shows owner's
>>>> + stacktrace. Requires --use-bpf.
>>>>
>>>> -Y::
>>>> --type-filter=<value>::
>>>> diff --git a/tools/perf/builtin-lock.c b/tools/perf/builtin-lock.c
>>>> index 9bebc186286f..05e7bc30488a 100644
>>>> --- a/tools/perf/builtin-lock.c
>>>> +++ b/tools/perf/builtin-lock.c
>>>> @@ -1817,6 +1817,22 @@ static void print_contention_result(struct lock_contention *con)
>>>> break;
>>>> }
>>>>
>>>> + if (con->owner && con->save_callstack && verbose > 0) {
>>>> + struct rb_root root = RB_ROOT;
>>>> +
>>>> + if (symbol_conf.field_sep)
>>>> + fprintf(lock_output, "# owner stack trace:\n");
>>>> + else
>>>> + fprintf(lock_output, "\n=== owner stack trace ===\n\n");
>>>> + while ((st = pop_owner_stack_trace(con)))
>>>> + insert_to(&root, st, compare);
>>>> +
>>>> + while ((st = pop_from(&root))) {
>>>> + print_lock_stat(con, st);
>>>> + free(st);
>>>> + }
>>>> + }
>>>> +
>>>> if (print_nr_entries) {
>>>> /* update the total/bad stats */
>>>> while ((st = pop_from_result())) {
>>>> @@ -1962,8 +1978,10 @@ static int check_lock_contention_options(const struct option *options,
>>>> }
>>>> }
>>>>
>>>> - if (show_lock_owner)
>>>> - show_thread_stats = true;
>>>> + if (show_lock_owner && !show_thread_stats) {
>>>> + pr_warning("Now -o try to show owner's callstack instead of pid and comm.\n");
>>>> + pr_warning("Please use -t option too to keep the old behavior.\n");
>>>> + }
>>>>
>>>> return 0;
>>>> }
>>>> diff --git a/tools/perf/util/bpf_lock_contention.c b/tools/perf/util/bpf_lock_contention.c
>>>> index 76542b86e83f..16f4deba69ec 100644
>>>> --- a/tools/perf/util/bpf_lock_contention.c
>>>> +++ b/tools/perf/util/bpf_lock_contention.c
>>>> @@ -549,6 +549,63 @@ static const char *lock_contention_get_name(struct lock_contention *con,
>>>> return name_buf;
>>>> }
>>>>
>>>> +struct lock_stat *pop_owner_stack_trace(struct lock_contention *con)
>>>> +{
>>>> + int stacks_fd, stat_fd;
>>>> + u64 *stack_trace = NULL;
>>>> + s32 stack_id;
>>>> + struct contention_key ckey = {};
>>>> + struct contention_data cdata = {};
>>>> + size_t stack_size = con->max_stack * sizeof(*stack_trace);
>>>> + struct lock_stat *st = NULL;
>>>> +
>>>> + stacks_fd = bpf_map__fd(skel->maps.owner_stacks);
>>>> + stat_fd = bpf_map__fd(skel->maps.owner_stat);
>>>> + if (!stacks_fd || !stat_fd)
>>>> + goto out_err;
>>>> +
>>>> + stack_trace = zalloc(stack_size);
>>>> + if (stack_trace == NULL)
>>>> + goto out_err;
>>>> +
>>>> + if (bpf_map_get_next_key(stacks_fd, NULL, stack_trace))
>>>> + goto out_err;
>>>> +
>>>> + bpf_map_lookup_elem(stacks_fd, stack_trace, &stack_id);
>>>> + ckey.stack_id = stack_id;
>>>> + bpf_map_lookup_elem(stat_fd, &ckey, &cdata);
>>>> +
>>>> + st = zalloc(sizeof(struct lock_stat));
>>>> + if (!st)
>>>> + goto out_err;
>>>> +
>>>> + st->name = strdup(stack_trace[0] ? lock_contention_get_name(con, NULL, stack_trace, 0) :
>>>> + "unknown");
>>>
>>> Hi,
>>>
>>> I am hitting a compilation issue with this change. Sorry for responding late. I tried with change from tmp.perf-tools-next and hit below issue:
>>>
>>>
>>> CC util/bpf_lock_contention.o
>>> util/bpf_lock_contention.c: In function ‘lock_contention_get_name’:
>>> cc1: error: function may return address of local variable [-Werror=return-local-addr]
>>> util/bpf_lock_contention.c:470:45: note: declared here
>>> 470 | struct contention_task_data task;
>>> | ^~~~
>>> cc1: all warnings being treated as errors
>>> make[4]: *** [/root/perf-tools-next/tools/build/Makefile.build:85: util/bpf_lock_contention.o] Error 1
>>> make[4]: *** Waiting for unfinished jobs....
>>> LD perf-in.o
>>> make[3]: *** [/root/perf-tools-next/tools/build/Makefile.build:138: util] Error 2
>>> make[2]: *** [Makefile.perf:822: perf-util-in.o] Error 2
>>> make[1]: *** [Makefile.perf:321: sub-make] Error 2
>>> make: *** [Makefile:76: all] Error 2
>>
>> Thanks for the report. I've noticed that and also found this error:
>>
>> In file included from util/lock-contention.c:4:0:
>> util/lock-contention.h:192:19: error: no previous prototype for 'pop_owner_stack_trace' [-Werror=missing-prototypes]
>> struct lock_stat *pop_owner_stack_trace(struct lock_contention *con)
>> ^~~~~~~~~~~~~~~~~~~~~
>> util/lock-contention.h: In function 'pop_owner_stack_trace':
>> util/lock-contention.h:192:65: error: unused parameter 'con' [-Werror=unused-parameter]
>> struct lock_stat *pop_owner_stack_trace(struct lock_contention *con)
>> ^~~
>>
>> Removed this series from tmp.perf-tools-next.
>>
>> Thanks,
>> Namhyung
>>
>>>
>>>
>>> Code snippet:
>>>
>>> if (con->aggr_mode == LOCK_AGGR_TASK) {
>>> struct contention_task_data task;
>>> int pid = key->pid;
>>> int task_fd = bpf_map__fd(skel->maps.task_data);
>>>
>>> /* do not update idle comm which contains CPU number */
>>> if (pid) {
>>> struct thread *t = machine__findnew_thread(machine, /*pid=*/-1, pid);
>>>
>>> if (t == NULL)
>>> return name;
>>> if (!bpf_map_lookup_elem(task_fd, &pid, &task) &&
>>> thread__set_comm(t, task.comm, /*timestamp=*/0))
>>> name = task.comm;
>>> }
>>> return name;
>>> }
>>>
>>>
>>> We are calling lock_contention_get_name with second argument as NULL .
>>> Though error above points to “contention_task_data”, I think the local variable here is for “name” ?
>>>
>>>
>>> Thanks
>>> Athira
>>>
>>>> + if (!st->name)
>>>> + goto out_err;
>>>> +
>>>> + st->flags = cdata.flags;
>>>> + st->nr_contended = cdata.count;
>>>> + st->wait_time_total = cdata.total_time;
>>>> + st->wait_time_max = cdata.max_time;
>>>> + st->wait_time_min = cdata.min_time;
>>>> + st->callstack = stack_trace;
>>>> +
>>>> + if (cdata.count)
>>>> + st->avg_wait_time = cdata.total_time / cdata.count;
>>>> +
>>>> + bpf_map_delete_elem(stacks_fd, stack_trace);
>>>> + bpf_map_delete_elem(stat_fd, &ckey);
>>>> +
>>>> + return st;
>>>> +
>>>> +out_err:
>>>> + free(stack_trace);
>>>> + free(st);
>>>> +
>>>> + return NULL;
>>>> +}
>>>> +
>>>> int lock_contention_read(struct lock_contention *con)
>>>> {
>>>> int fd, stack, err = 0;
>>>> diff --git a/tools/perf/util/lock-contention.h b/tools/perf/util/lock-contention.h
>>>> index a09f7fe877df..97fd33c57f17 100644
>>>> --- a/tools/perf/util/lock-contention.h
>>>> +++ b/tools/perf/util/lock-contention.h
>>>> @@ -168,6 +168,8 @@ int lock_contention_stop(void);
>>>> int lock_contention_read(struct lock_contention *con);
>>>> int lock_contention_finish(struct lock_contention *con);
>>>>
>>>> +struct lock_stat *pop_owner_stack_trace(struct lock_contention *con);
>>>> +
>>>> #else /* !HAVE_BPF_SKEL */
>>>>
>>>> static inline int lock_contention_prepare(struct lock_contention *con __maybe_unused)
>>>> @@ -187,6 +189,11 @@ static inline int lock_contention_read(struct lock_contention *con __maybe_unuse
>>>> return 0;
>>>> }
>>>>
>>>> +struct lock_stat *pop_owner_stack_trace(struct lock_contention *con)
>>>> +{
>>>> + return NULL;
>>>> +}
>>>> +
>>>> #endif /* HAVE_BPF_SKEL */
>>>>
>>>> #endif /* PERF_LOCK_CONTENTION_H */
>>>> --
>>>> 2.48.1.658.g4767266eb4-goog
>>>>
>>>>
>>>
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