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| author |   Namhyung Kim <namhyung@kernel.org> | 2025-05-15 11:10:42 -0700 |
|---|---|---|
| committer |   Arnaldo Carvalho de Melo <acme@redhat.com> | 2025-05-31 08:45:24 -0300 |
| commit | 0df14c1f1ed530ba21b603a2e282589c034367da (patch) | |
| tree | 4a24285744a1a9f95bdeb47f0ccc18df6aa9149b | |
| parent | perf trace: Set errpid to false for rseq and set_robust_list (diff) | |
| download | linux-rng-0df14c1f1ed530ba21b603a2e282589c034367da.tar.xz linux-rng-0df14c1f1ed530ba21b603a2e282589c034367da.zip | |
perf lock contention: Reject more than 10ms delays for safety
Delaying kernel operations can be dangerous and the kernel may kill
(non-sleepable) BPF programs running for long in the future.
Limit the max delay to 10ms and update the document about it.
$ sudo ./perf lock con -abl -J 100000us@cgroup_mutex true
lock delay is too long: 100000us (> 10ms)
Usage: perf lock contention [<options>]
-J, --inject-delay <TIME@FUNC>
Inject delays to specific locks
Suggested-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Song Liu <song@kernel.org>
Link: https://lore.kernel.org/r/20250515181042.555189-1-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
| -rw-r--r-- | tools/perf/Documentation/perf-lock.txt | 8 | ||||
| -rw-r--r-- | tools/perf/builtin-lock.c | 5 |
2 files changed, 11 insertions, 2 deletions
diff --git a/tools/perf/Documentation/perf-lock.txt b/tools/perf/Documentation/perf-lock.txt index 2d9aecf63042..c17b3e318169 100644 --- a/tools/perf/Documentation/perf-lock.txt +++ b/tools/perf/Documentation/perf-lock.txt @@ -224,8 +224,12 @@ CONTENTION OPTIONS only with -b/--use-bpf. The 'time' is specified in nsec but it can have a unit suffix. Available - units are "ms" and "us". Note that it will busy-wait after it gets the - lock. Please use it at your own risk. + units are "ms", "us" and "ns". Currently it accepts up to 10ms of delays + for safety reasons. + + Note that it will busy-wait after it gets the lock. Delaying locks can + have significant consequences including potential kernel crashes. Please + use it at your own risk. SEE ALSO diff --git a/tools/perf/builtin-lock.c b/tools/perf/builtin-lock.c index 41f6f3d2b779..3b3ade7a39ca 100644 --- a/tools/perf/builtin-lock.c +++ b/tools/perf/builtin-lock.c @@ -2537,6 +2537,11 @@ static bool add_lock_delay(char *spec) return false; } + if (duration > 10 * 1000 * 1000) { + pr_err("lock delay is too long: %s (> 10ms)\n", spec); + return false; + } + tmp = realloc(delays, (nr_delays + 1) * sizeof(*delays)); if (tmp == NULL) { pr_err("Memory allocation failure\n"); |