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perf top: Expand the range of multithreaded phase

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In __cmd_top(), perf_set_multithreaded() is used to enable
pthread_rwlock, thus down_read() and down_write () are not nops,
handling concurrency problems

Then 'perf top' uses perf_set_singlethreaded(), switching to the single
threaded phase, assuming that no thread concurrency will happen later.

However, a use after free problem could occur in the single threaded
phase, the concurrent procedure is this:

display_thread                              process_thread
--------------                              --------------
thread__comm_len
  -> thread__comm_str
    -> __thread__comm_str(thread)
                                            thread__delete
                                             -> comm__free
                                              -> comm_str__put
                                               -> zfree(&cs->str)
    -> thread->comm_len = strlen(comm);

Since in single thread phase, perf_singlethreaded is true, down_read()
and down_write() do nothing to avoid concurrency problems.

This patch moves the perf_set_singlethreaded() call to the function tail
to expand the multithreaded phase range, making display_thread() and
process_thread() concurrency safe.

Reviewed-by: Yunfeng Ye <yeyunfeng@huawei.com>
Signed-off-by: Hangliang Lai  <laihangliang1@huawei.com>
Co-developed-by: Wenyu Liu <liuwenyu7@huawei.com>
Acked-by: Namhyung Kim <namhyung@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Feilong Lin <linfeilong@huawei.com>
Cc: Hewenliang <hewenliang4@huawei.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Link: https://lore.kernel.org/r/20230411013224.2079-1-laihangliang1@huawei.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
This commit is contained in:
Hangliang Lai 2023-04-11 09:32:24 +08:00 committed by Arnaldo Carvalho de Melo
parent ed4da0d3de
commit eab5051788
1 changed files with 2 additions and 2 deletions
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4
tools/perf/builtin-top.c
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@ -1276,8 +1276,7 @@ static int __cmd_top(struct perf_top *top)
top->evlist->core.threads, true, false,
top->nr_threads_synthesize);
if (top->nr_threads_synthesize > 1)
perf_set_singlethreaded();
perf_set_multithreaded();
if (perf_hpp_list.socket) {
ret = perf_env__read_cpu_topology_map(&perf_env);
@ -1355,6 +1354,7 @@ out_join:
out_join_thread:
cond_signal(&top->qe.cond);
pthread_join(thread_process, NULL);
perf_set_singlethreaded();
return ret;
}