Re: [PATCH v12 15/20] perf intel-tpebs: Fix race in tpebs_stop() and tpebs_cmd.out fd handling

[sashiko-bot@kernel.org]

> In tpebs_stop(), read tpebs_reader_thread into a local variable before
> releasing tpebs_mtx to call pthread_join().
> 
> Transfer ownership of tpebs_cmd.out to __sample_reader() by passing it
> as the thread argument and setting tpebs_cmd.out = -1 in
> evsel__tpebs_open() so tpebs_stop() does not double-close the fd closed
> by perf_session__delete(). Also reset tpebs_cmd.pid = 0 and
> tpebs_cmd.out = -1 and return early if start_command() fails in
> evsel__tpebs_start_perf_record(), as start_command() closes the pipe
> internally and may leave cmd->pid = -1 on error.
> 
> Serialize tpebs_send_record_cmd() with teardown via tpebs_cmd_in_flight
> and tpebs_cmd_cond, newline-terminate control commands so consecutive
> writes cannot coalesce in evlist__ctlfd_recv(), check
> check_if_command_finished(&tpebs_cmd) under tpebs_mtx only when not
> stopping, ignore late samples in process_sample_event() once
> tpebs_stopping is set, and guard evsel__tpebs_open() against a
> concurrent tpebs_stop() with tpebs_gen, tpebs_enabled, and
> tpebs_stopping across closing the fds and finish_command().
> 
> Include <pthread.h>, <signal.h>, <stdint.h>, <stdlib.h>, <string.h>, and
> <unistd.h> explicitly.
> 
> Fixes: 8db5cabcf1b6 ("perf stat: Fork and launch 'perf record' when 'perf stat' needs to get retire latency value for a metric.")
> Fixes: bded0398ac19 ("perf tpebs: Fix concurrent stop races and PID reuse hazards in tpebs_stop")
> Signed-off-by: Ian Rogers <irogers@google.com>

Sashiko has reviewed this patch and found no issues.

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Sashiko AI review · https://sashiko.dev/#/patchset/20261111174213.3526604-1-irogers@google.com?part=15