Port LockImpl, Lock, and ConditionVariable to pthreads-supporting platforms.

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@567 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 40 insertions, 37 deletions

diff --git a/base/condition_variable.h b/base/condition_variable.h
index bdb9a19..f30ffba 100644
--- a/base/condition_variable.h
+++ b/base/condition_variable.h
@@ -27,37 +27,35 @@
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
-// ConditionVariable is a reasonable attempt at simulating
-// the newer Posix and Vista-only construct for condition variable
-// synchronization.  This functionality is very helpful for having several
-// threads wait for an event, as is common with a thread pool
-// managed by a master.  The meaning of such an event in the
-// (worker) thread pool scenario is that additional tasks are
-// now available for processing.  It is used in Chrome in the
-// DNS prefetching system to notify worker threads that a queue
-// now has items (tasks) which need to be tended to.
-// A related use would have a pool manager waiting on a
-// ConditionVariable, waiting for a thread in the pool to announce
-// (signal) that there is now more room in a (bounded size) communications
-// queue for the manager to deposit tasks, or, as a second example, that
-// the queue of tasks is completely empty and all workers are waiting.
-
+// ConditionVariable wraps pthreads condition variable synchronization or, on
+// Windows, simulates it.  This functionality is very helpful for having
+// several threads wait for an event, as is common with a thread pool managed
+// by a master.  The meaning of such an event in the (worker) thread pool
+// scenario is that additional tasks are now available for processing.  It is
+// used in Chrome in the DNS prefetching system to notify worker threads that
+// a queue now has items (tasks) which need to be tended to.  A related use
+// would have a pool manager waiting on a ConditionVariable, waiting for a
+// thread in the pool to announce (signal) that there is now more room in a
+// (bounded size) communications queue for the manager to deposit tasks, or,
+// as a second example, that the queue of tasks is completely empty and all
+// workers are waiting.
+//
 // USAGE NOTE 1: spurious signal events are possible with this and
 // most implementations of condition variables.  As a result, be
 // *sure* to retest your condition before proceeding.  The following
 // is a good example of doing this correctly:
-
+//
 // while (!work_to_be_done()) Wait(...);
-
+//
 // In contrast do NOT do the following:
-
+//
 // if (!work_to_be_done()) Wait(...);  // Don't do this.
-
+//
 // Especially avoid the above if you are relying on some other thread only
 // issuing a signal up *if* there is work-to-do.  There can/will
 // be spurious signals.  Recheck state on waiting thread before
 // assuming the signal was intentional. Caveat caller ;-).
-
+//
 // USAGE NOTE 2: Broadcast() frees up all waiting threads at once,
 // which leads to contention for the locks they all held when they
 // called Wait().  This results in POOR performance.  A much better
@@ -65,11 +63,11 @@
 // thread (upon exiting Wait()) call Signal() to free up another
 // Wait'ing thread.  Look at condition_variable_unittest.cc for
 // both examples.
-
+//
 // Broadcast() can be used nicely during teardown, as it gets the job
 // done, and leaves no sleeping threads... and performance is less
 // critical at that point.
-
+//
 // The semantics of Broadcast() are carefully crafted so that *all*
 // threads that were waiting when the request was made will indeed
 // get signaled.  Some implementations mess up, and don't signal them
@@ -77,7 +75,7 @@
 // for a while while waiting threads come around).  This implementation
 // appears correct, as it will not "lose" any signals, and will guarantee
 // that all threads get signaled by Broadcast().
-
+//
 // This implementation offers support for "performance" in its selection of
 // which thread to revive.  Performance, in direct contrast with "fairness,"
 // assures that the thread that most recently began to Wait() is selected by
@@ -85,20 +83,18 @@
 // thread that has Wait()ed the longest is selected. The default policy
 // may improve performance, as the selected thread may have a greater chance of
 // having some of its stack data in various CPU caches.
-
+//
 // For a discussion of the many very subtle implementation details, see the FAQ
-// at the end of condition_variable.cc.
+// at the end of condition_variable_win.cc.
 
-#ifndef BASE_CONDITION_VARIABLE_H__
-#define BASE_CONDITION_VARIABLE_H__
+#ifndef BASE_CONDITION_VARIABLE_H_
+#define BASE_CONDITION_VARIABLE_H_
 
 #include "base/lock.h"
 #include "base/logging.h"
 #include "base/scoped_ptr.h"
 #include "base/time.h"
 
-class Lock;
-
 class ConditionVariable {
  public:
   // Construct a cv for use with ONLY one user lock.
@@ -108,12 +104,8 @@ class ConditionVariable {
 
   // Wait() releases the caller's critical section atomically as it starts to
   // sleep, and the reacquires it when it is signaled.
+  void Wait();
   void TimedWait(const TimeDelta& max_time);
-  void Wait() {
-    // Default to "wait forever" timing, which means have to get a Signal()
-    // or Broadcast() to come out of this wait state.
-    TimedWait(TimeDelta::FromMilliseconds(INFINITE));
-  }
 
   // Broadcast() revives all waiting threads.
   void Broadcast();
@@ -121,6 +113,9 @@ class ConditionVariable {
   void Signal();
 
  private:
+
+#if defined(OS_WIN)
+
   // Define Event class that is used to form circularly linked lists.
   // The list container is an element with NULL as its handle_ value.
   // The actual list elements have a non-zero handle_ value.
@@ -161,7 +156,7 @@ class ConditionVariable {
     HANDLE handle_;
     Event* next_;
     Event* prev_;
-    DISALLOW_EVIL_CONSTRUCTORS(Event);
+    DISALLOW_COPY_AND_ASSIGN(Event);
   };
 
   // Note that RUNNING is an unlikely number to have in RAM by accident.
@@ -176,6 +171,7 @@ class ConditionVariable {
 
   // Private critical section for access to member data.
   Lock internal_lock_;
+
   // Lock that is acquired before calling Wait().
   Lock& user_lock_;
 
@@ -189,7 +185,14 @@ class ConditionVariable {
   // The number of allocated, but not yet deleted events.
   int allocation_counter_;
 
-  DISALLOW_EVIL_CONSTRUCTORS(ConditionVariable);
+#elif defined(OS_POSIX)
+
+  pthread_cond_t condition_;
+  pthread_mutex_t* user_mutex_;
+
+#endif
+
+  DISALLOW_COPY_AND_ASSIGN(ConditionVariable);
 };
 
-#endif  // BASE_CONDITION_VARIABLE_H__
+#endif  // BASE_CONDITION_VARIABLE_H_