Rollback f040e96

PiperOrigin-RevId: 802588083
Change-Id: Ibea44bd227dda2f4ebc7e24890426faa7a83b36b

Author: Abseil Team

absl/base/internal/sysinfo.cc

@@ -135,69 +135,6 @@ int Win32NumCPUs() {
 
 #endif
 
-#if defined(__linux__)
-// Kinda like perror, but without allocating. At least, mostly...
-void PerrorNoAlloc(const char* msg) {
-  // strerror might allocate, theoretically. In practice, it doesn't do so on
-  // glibc unless you provide an invalid errno, and never allocates on musl.
-  char *errmsg = strerror(errno);
-
-  // snprintf isn't technically on the async-signal-safe list, but, in practice,
-  // it doesn't allocate.
-  char buf[1024];
-  int len = snprintf(buf, sizeof(buf), "%s: %s\n", msg, errmsg);
-  if (len > 0) {
-    if ((unsigned)len > sizeof(buf)) len = sizeof(buf);
-    ABSL_ATTRIBUTE_UNUSED auto ret = write(2, buf, static_cast<size_t>(len));
-  }
-}
-
-// Returns the number of possible cpus by parsing a sysfs string.
-int ParseSysFsPossibleCPUs(const char* str, size_t len) {
-  if (len == 0) return 1;
-  // Find the last number in the line and parse that -- that'll be the highest
-  // cpu number.
-  for (int i = static_cast<int>(len - 1); i >= 0; --i) {
-    if (!isdigit(str[i])) return atoi(&str[i+1]) + 1;  // NOLINT
-  }
-  return atoi(str) + 1;  // NOLINT
-}
-
-int GetNumPossibleCpusFromSysfs() {
-  // The "possible" file exists since Linux 2.6.26.
-  //
-  // It contains a value such as "0-127" (meaning you have 128 CPUs, numbered 0
-  // through 127). The format used here also supports strings like: "0,2,4-7" to
-  // describe discontiguous ids, but that cannot actually happen here, since
-  // "possible" CPU numbers are always contiguous from 0 to the maximum.
-  int fd;
-  do {
-    fd = open("/sys/devices/system/cpu/possible", O_RDONLY | O_CLOEXEC);
-  } while (fd < 0 && errno == EINTR);
-
-  if (fd < 0) {
-    PerrorNoAlloc("GetNumPossibleCpusFromSysfs: open() failed");
-    abort();
-  }
-
-  char buf[1024];
-  ssize_t len;
-  do {
-    len = read(fd, buf, sizeof(buf) - 1);
-  } while (len < 0 && errno == EINTR);
-
-  if (len <= 0) {
-    PerrorNoAlloc("GetNumPossibleCpusFromSysfs: read() failed");
-    abort();
-  }
-  close(fd);
-
-  if (buf[len - 1] == '\n') --len;
-  buf[len] = '\0';
-  return ParseSysFsPossibleCPUs(buf, static_cast<size_t>(len));
-}
-#endif
-
 }  // namespace
 
 static int GetNumCPUs() {
@@ -208,8 +145,6 @@ static int GetNumCPUs() {
   return hardware_concurrency ? hardware_concurrency : 1;
 #elif defined(_AIX)
   return sysconf(_SC_NPROCESSORS_ONLN);
-#elif defined(__linux__)
-  return GetNumPossibleCpusFromSysfs();
 #else
   // Other possibilities:
   //  - Read /sys/devices/system/cpu/online and use cpumask_parse()