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perf trace: Always print return value for syscalls returning a pid

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[ Upstream commit c7a48ea9b919e2fa0e4a1d9938fdb03e9afe276c ]

The syscalls that were consistently observed were set_robust_list and
rseq. This is because perf cannot find their child process.

This change ensures that the return value is always printed.

Before:
     0.256 ( 0.001 ms): set_robust_list(head: 0x7f09c77dba20, len: 24)                        =
     0.259 ( 0.001 ms): rseq(rseq: 0x7f09c77dc0e0, rseq_len: 32, sig: 1392848979)             =
After:
     0.270 ( 0.002 ms): set_robust_list(head: 0x7f0bb14a6a20, len: 24)                        = 0
     0.273 ( 0.002 ms): rseq(rseq: 0x7f0bb14a70e0, rseq_len: 32, sig: 1392848979)             = 0

Committer notes:

As discussed in the thread in the Link: tag below, these two don't
return a pid, but for syscalls returning one, we need to print the
result and if we manage to find the children in 'perf trace' data
structures, then print its name as well.

Fixes: 11c8e39f51 ("perf trace: Infrastructure to show COMM strings for syscalls returning PIDs")
Reviewed-by: Howard Chu <howardchu95@gmail.com>
Signed-off-by: Anubhav Shelat <ashelat@redhat.com>
Acked-by: Namhyung Kim <namhyung@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Dapeng Mi <dapeng1.mi@linux.intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: James Clark <james.clark@linaro.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Michael Petlan <mpetlan@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://lore.kernel.org/r/20250403160411.159238-2-ashelat@redhat.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Anubhav Shelat
2025-04-03 12:04:12 -04:00
committed by Greg Kroah-Hartman
parent 494395071e
commit 7101de2396
1 changed files with 1 additions and 1 deletions
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2
tools/perf/builtin-trace.c
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@@ -2586,8 +2586,8 @@ errno_print: {
else if (sc->fmt->errpid) { else if (sc->fmt->errpid) {
struct thread *child = machine__find_thread(trace->host, ret, ret); struct thread *child = machine__find_thread(trace->host, ret, ret);
fprintf(trace->output, "%ld", ret);
if (child != NULL) { if (child != NULL) {
fprintf(trace->output, "%ld", ret);
if (thread__comm_set(child)) if (thread__comm_set(child))
fprintf(trace->output, " (%s)", thread__comm_str(child)); fprintf(trace->output, " (%s)", thread__comm_str(child));
thread__put(child); thread__put(child);