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perf record: Fix teardown hang on system-wide multi-threaded sessions

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Under system-wide (-a) parallel streaming mode (--threads=cpu),
background recording threads can be inundated by a continuous
firehose of hardware samples generated by the OS. In this state,
a background thread's local hit count remains unequal to its
sample count, causing it to bypass the blocking fdarray__poll()
call entirely on each iteration of its recording loop.

Because the termination check relies on the POLLHUP event status
populated specifically by fdarray__poll(), bypassing it prevents
the background thread from ever recognizing that its control pipe
was closed by the main thread. This traps the background thread
in an infinite recording loop, hanging the main thread indefinitely
as it awaits a termination acknowledgment that never arrives.

Ensure teardown completion by adding explicit evlist__disable()
calls in the main thread's cleanup paths at out_child: and
out_child_no_flush:. Additionally, patch fdarray__filter() to
respect the fdarray_flag__nonfilterable flag, preventing it
from incorrectly setting the background thread's control pipe
file descriptor to -1 and clearing its revents mask upon
processing termination POLLHUP signals.

Fixes: f94563fac2 ("perf record: fix poll storm when monitored threads exit")
Assisted-by: Antigravity:gemini-3.5-flash
Signed-off-by: Ian Rogers <irogers@google.com>
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
This commit is contained in:
Ian Rogers 2026-07-09 22:39:06 -07:00 committed by Namhyung Kim
parent d3c9fca531
commit fb4751e79c
2 changed files with 6 additions and 2 deletions
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6
tools/lib/api/fd/array.c
View File

@ -115,6 +115,9 @@ int fdarray__filter(struct fdarray *fda, short revents,
return 0;
for (fd = 0; fd < fda->nr; ++fd) {
if (fda->priv[fd].flags & fdarray_flag__nonfilterable)
continue;
if (!fda->entries[fd].events)
continue;
@ -132,8 +135,7 @@ int fdarray__filter(struct fdarray *fda, short revents,
continue;
}
if (!(fda->priv[fd].flags & fdarray_flag__nonfilterable))
++nr;
++nr;
}
return nr;

2
tools/perf/builtin-record.c
View File

@ -2890,11 +2890,13 @@ static int __cmd_record(struct record *rec, int argc, const char **argv)
record__synthesize_workload(rec, true);
out_child:
evlist__disable(rec->evlist);
record__stop_threads(rec);
record__mmap_read_all(rec, true);
goto out_free_threads;
out_child_no_flush:
/* mmap read already failed — retrying would just fail again */
evlist__disable(rec->evlist);
record__stop_threads(rec);
out_free_threads:
record__free_thread_data(rec);