Copilot commented on code in PR #3282:
URL: https://github.com/apache/brpc/pull/3282#discussion_r3141618253
##########
src/bvar/default_variables.cpp:
##########
@@ -81,7 +81,12 @@ static bool read_proc_status(ProcStat &stat) {
// see http://man7.org/linux/man-pages/man5/proc.5.html
butil::ScopedFILE fp("/proc/self/stat", "r");
if (NULL == fp) {
- PLOG_ONCE(WARNING) << "Fail to open /proc/self/stat";
+ static bool ever_printed_stat_err = false;
+ if (!ever_printed_stat_err) {
+ fprintf(stderr, "WARNING: Fail to open /proc/self/stat, errno=%d. "
+ "Process status related bvars will be
unavailable.\n", errno);
+ ever_printed_stat_err = true;
Review Comment:
`ever_printed_stat_err` is a non-atomic function-local static that can be
read/written concurrently by the sampler thread(s), which is a data race/UB and
can also result in multiple prints. Use a thread-safe one-time guard (e.g.,
`butil::static_atomic<bool>` with `exchange`, `std::atomic<bool>`, or
`pthread_once`) for the print-once behavior.
##########
src/bvar/default_variables.cpp:
##########
@@ -94,7 +99,8 @@ static bool read_proc_status(ProcStat &stat) {
&stat.flags, &stat.minflt, &stat.cminflt, &stat.majflt,
&stat.cmajflt, &stat.utime, &stat.stime, &stat.cutime,
&stat.cstime,
&stat.priority, &stat.nice, &stat.num_threads) != 19) {
- PLOG(WARNING) << "Fail to fscanf";
+ fprintf(stderr, "WARNING: Fail to fscanf /proc/self/stat, errno=%d. "
+ "Process status related bvars will be unavailable.\n",
errno);
return false;
Review Comment:
This warning prints `errno` for an `fscanf` parse failure, but `fscanf`
often fails without setting `errno` (so it may misleadingly print `errno=0`).
Consider resetting `errno` before `fscanf` and/or reporting the `fscanf` return
value / `ferror(fp)` (and only include `errno`/`strerror` when an actual I/O
error occurred).
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