diff options
| author | Ian Rogers <irogers@google.com> | 2026-10-01 23:54:39 -0700 |
|---|---|---|
| committer | Arnaldo Carvalho de Melo <acme@redhat.com> | 2026-10-02 18:04:37 +0200 |
| commit | 1858a4df3ecbbdf5dce6d4df9edbebed403015ed (patch) | |
| tree | b6ee3f233efaeb8aab67a1ecccba50d5db7c26c9 | |
| parent | 148cd3adf2df9e53fd9b3070ae1178d4876f8c67 (diff) | |
| download | linux-next-1858a4df3ecbbdf5dce6d4df9edbebed403015ed.tar.gz linux-next-1858a4df3ecbbdf5dce6d4df9edbebed403015ed.zip | |
perf trace: Only call bpf_get_current_pid_tgid() when filtering tasks
In task_traced(), bpf_get_current_pid_tgid() was called before checking
has_pids_to_trace. Because BPF helper calls are not marked pure, the
compiler cannot sink the call past the has_pids_to_trace check, so the
helper was called on every syscall enter and exit even when tracing
system-wide.
Check has_pids_to_trace before calling bpf_get_current_pid_tgid().
Suggested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Assisted-by: Antigravity:gemini-3.1-pro
Signed-off-by: Ian Rogers <irogers@google.com>
Cc: Howard Chu <howardchu95@gmail.com>
Cc: Jakub Brnak <jbrnak@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
| -rw-r--r-- | tools/perf/util/bpf_skel/augmented_raw_syscalls.bpf.c | 6 |
1 files changed, 4 insertions, 2 deletions
diff --git a/tools/perf/util/bpf_skel/augmented_raw_syscalls.bpf.c b/tools/perf/util/bpf_skel/augmented_raw_syscalls.bpf.c index d16e55706335..0b2ef9541f84 100644 --- a/tools/perf/util/bpf_skel/augmented_raw_syscalls.bpf.c +++ b/tools/perf/util/bpf_skel/augmented_raw_syscalls.bpf.c @@ -494,13 +494,15 @@ static bool pid_filter__has(struct pids_filtered *pids, pid_t pid) static bool task_traced(void) { - u64 pid_tgid = bpf_get_current_pid_tgid(); - pid_t pid = uses_tgid ? pid_tgid >> 32 : (pid_t)pid_tgid; + u64 pid_tgid; + pid_t pid; bool *traced; if (!has_pids_to_trace) return true; + pid_tgid = bpf_get_current_pid_tgid(); + pid = uses_tgid ? pid_tgid >> 32 : (pid_t)pid_tgid; traced = bpf_map_lookup_elem(&pids_to_trace, &pid); return traced && *traced; } |