commit a8cf3b7cbd265856797526d391cf951019a2a66b
author Mirko Bonadei <mbonadei@webrtc.org> Fri May 24 11:47:23 2019
committer Commit Bot <commit-bot@chromium.org> Fri May 24 12:59:14 2019
tree 650f82584f56c6dca2bd02fdbd84cd5cc2f99fe7
parent fadb1811a8c16c590d43c0e0d76806802e2c695c

Ensure CpuInfo::DetectNumberOfCores is > 0 and thread safe.

This CL adds error handling for sysconf, which can return -1 and
adds an RTC_CHECK_GT to ensure the value returned is always greater
than 0.

On top of that CpuInfo::DetectNumberOfCores is made thread safe because
the static local variable is initialized with the right values istead
of 0.

Bug: None
Change-Id: I294684e7380b12cda55ec8d6c7a90e132dc3af85
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/138210
Commit-Queue: Mirko Bonadei <mbonadei@webrtc.org>
Reviewed-by: Niels Moller <nisse@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#28057}

system_wrappers/source/cpu_info.cc

diff --git a/system_wrappers/source/cpu_info.cc b/system_wrappers/source/cpu_info.cc
index 6bcdd5f..7288c67 100644
--- a/system_wrappers/source/cpu_info.cc
+++ b/system_wrappers/source/cpu_info.cc
@@ -24,8 +24,7 @@
 
 namespace internal {
 static int DetectNumberOfCores() {
-  // We fall back on assuming a single core in case of errors.
-  int number_of_cores = 1;
+  int number_of_cores;
 
 #if defined(WEBRTC_WIN)
   SYSTEM_INFO si;
@@ -33,6 +32,10 @@
   number_of_cores = static_cast<int>(si.dwNumberOfProcessors);
 #elif defined(WEBRTC_LINUX) || defined(WEBRTC_ANDROID)
   number_of_cores = static_cast<int>(sysconf(_SC_NPROCESSORS_ONLN));
+  if (number_of_cores < 0) {
+    RTC_LOG(LS_ERROR) << "Failed to get number of cores";
+    number_of_cores = 1;
+  }
 #elif defined(WEBRTC_MAC) || defined(WEBRTC_IOS)
   int name[] = {CTL_HW, HW_AVAILCPU};
   size_t size = sizeof(number_of_cores);
@@ -44,10 +47,12 @@
   number_of_cores = zx_system_get_num_cpus();
 #else
   RTC_LOG(LS_ERROR) << "No function to get number of cores";
+  number_of_cores = 1;
 #endif
 
   RTC_LOG(LS_INFO) << "Available number of cores: " << number_of_cores;
 
+  RTC_CHECK_GT(number_of_cores, 0);
   return number_of_cores;
 }
 }  // namespace internal
@@ -59,9 +64,8 @@
   // is running in a sandbox, we may only be able to read the value once (before
   // the sandbox is initialized) and not thereafter.
   // For more information see crbug.com/176522.
-  static uint32_t logical_cpus = 0;
-  if (!logical_cpus)
-    logical_cpus = static_cast<uint32_t>(internal::DetectNumberOfCores());
+  static const uint32_t logical_cpus =
+      static_cast<uint32_t>(internal::DetectNumberOfCores());
   return logical_cpus;
 }