commit f8e389f3acdc2517562924239e2a188037393683
author Paul Wankadia <junyer@google.com> Wed Feb 24 01:58:12 2021 -0800
committer Paul Wankadia <junyer@google.com> Wed Feb 24 09:59:19 2021 +0000
tree 69a86732f066ec6224241473df6aac33fbe4413a
parent 377eca0e766aea181a15115689662ba2db5ee474

Make it easier to swap in a scalable reader-writer mutex.

Change-Id: I04837646dfb41c2b545af54312dac63f47473dd6
Reviewed-on: https://code-review.googlesource.com/c/re2/+/58430
Reviewed-by: Paul Wankadia <junyer@google.com>

re2/dfa.cc

diff --git a/re2/dfa.cc b/re2/dfa.cc
index 3f6571d..f292ff1 100644
--- a/re2/dfa.cc
+++ b/re2/dfa.cc
@@ -167,6 +167,9 @@
   typedef std::unordered_set<State*, StateHash, StateEqual> StateSet;
 
  private:
+  // Make it easier to swap in a scalable reader-writer mutex.
+  using CacheMutex = Mutex;
+
   enum {
     // Indices into start_ for unanchored searches.
     // Add kStartAnchored for anchored searches.
@@ -331,7 +334,7 @@
   // while holding cache_mutex_ for writing, to avoid interrupting other
   // readers.  Any State* pointers are only valid while cache_mutex_
   // is held.
-  Mutex cache_mutex_;
+  CacheMutex cache_mutex_;
   int64_t mem_budget_;     // Total memory budget for all States.
   int64_t state_budget_;   // Amount of memory remaining for new States.
   StateSet state_cache_;   // All States computed so far.
@@ -1106,7 +1109,7 @@
 
 class DFA::RWLocker {
  public:
-  explicit RWLocker(Mutex* mu);
+  explicit RWLocker(CacheMutex* mu);
   ~RWLocker();
 
   // If the lock is only held for reading right now,
@@ -1116,14 +1119,14 @@
   void LockForWriting();
 
  private:
-  Mutex* mu_;
+  CacheMutex* mu_;
   bool writing_;
 
   RWLocker(const RWLocker&) = delete;
   RWLocker& operator=(const RWLocker&) = delete;
 };
 
-DFA::RWLocker::RWLocker(Mutex* mu) : mu_(mu), writing_(false) {
+DFA::RWLocker::RWLocker(CacheMutex* mu) : mu_(mu), writing_(false) {
   mu_->ReaderLock();
 }