[2/4] mesos git commit: stout: Replace GCC intrinsics with std::atomic.

[jo...@apache.org]

stout: Replace GCC intrinsics with std::atomic.

MESOS-3326.

Review: https://reviews.apache.org/r/37876


Project: http://git-wip-us.apache.org/repos/asf/mesos/repo
Commit: http://git-wip-us.apache.org/repos/asf/mesos/commit/4a01850c
Tree: http://git-wip-us.apache.org/repos/asf/mesos/tree/4a01850c
Diff: http://git-wip-us.apache.org/repos/asf/mesos/diff/4a01850c

Branch: refs/heads/master
Commit: 4a01850c554048cfa53ca03d7d6e3cf901ce166d
Parents: 9411749
Author: Neil Conway <ne...@gmail.com>
Authored: Thu Sep 10 17:50:13 2015 -0700
Committer: Joris Van Remoortere <jo...@gmail.com>
Committed: Thu Sep 10 19:39:41 2015 -0700

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 .../3rdparty/stout/include/stout/os/posix/fork.hpp  | 16 +++++++---------
 1 file changed, 7 insertions(+), 9 deletions(-)
----------------------------------------------------------------------


http://git-wip-us.apache.org/repos/asf/mesos/blob/4a01850c/3rdparty/libprocess/3rdparty/stout/include/stout/os/posix/fork.hpp
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diff --git a/3rdparty/libprocess/3rdparty/stout/include/stout/os/posix/fork.hpp b/3rdparty/libprocess/3rdparty/stout/include/stout/os/posix/fork.hpp
index d43433a..7eb51e8 100644
--- a/3rdparty/libprocess/3rdparty/stout/include/stout/os/posix/fork.hpp
+++ b/3rdparty/libprocess/3rdparty/stout/include/stout/os/posix/fork.hpp
@@ -21,6 +21,7 @@
 #include <sys/types.h>
 #include <sys/wait.h>
 
+#include <atomic>
 #include <list>
 #include <memory>
 #include <set>
@@ -232,7 +233,7 @@ private:
       pid_t group;
       pid_t session;
 
-      bool set; // Has this been initialized?
+      std::atomic_bool set; // Has this been initialized?
     };
 
     std::shared_ptr<Memory> memory;
@@ -274,11 +275,11 @@ private:
   // Constructs a Tree (see above) from this fork template.
   Try<Tree> prepare() const
   {
-    static int forks = 0;
+    static std::atomic_int forks(0);
 
     // Each "instance" of an instantiated Fork needs a unique name for
     // creating shared memory.
-    int instance = __sync_fetch_and_add(&forks, 1);
+    int instance = forks.fetch_add(1);
 
     std::string name =
       "/stout-forks-" + stringify(getpid()) + stringify(instance);
@@ -312,7 +313,7 @@ private:
 
     Tree tree;
     tree.memory = std::shared_ptr<Tree::Memory>((Tree::Memory*)memory, deleter);
-    tree.memory->set = false;
+    tree.memory->set.store(false);
 
     for (size_t i = 0; i < children.size(); i++) {
       Try<Tree> tree_ = children[i].prepare();
@@ -340,7 +341,7 @@ private:
     process.parent = getppid();
     process.group = getpgid(0);
     process.session = getsid(0);
-    process.set = true;
+    process.set.store(true);
 
     // Copy it into shared memory.
     memcpy(tree.memory.get(), &process, sizeof(Tree::Memory));
@@ -381,10 +382,7 @@ private:
   {
     // Wait for the forked process.
     // TODO(benh): Don't wait forever?
-    while (!tree.memory->set) {
-      // Make sure we don't keep reading the value from a register.
-      __sync_synchronize();
-    }
+    while (!tree.memory->set.load());
 
     // All processes in the returned ProcessTree will have the
     // command-line of the top level process, since we construct the