Add LOCK_SHAREDMUTEX SSLLockType.

Summary: To take advantage of read locks.

Reviewed By: siyengar

Differential Revision: D5106090

fbshipit-source-id: a32afd698e9204196aa3d23f21a7d41803b2eb66

folly/io/async/SSLContext.cpp

@@ -19,6 +19,7 @@
 #include <folly/Format.h>
 #include <folly/Memory.h>
 #include <folly/Random.h>
+#include <folly/SharedMutex.h>
 #include <folly/SpinLock.h>
 #include <folly/ThreadId.h>
 
@@ -722,20 +723,32 @@ struct SSLLock {
       lockType(inLockType) {
   }
 
-  void lock() {
+  void lock(bool read) {
     if (lockType == SSLContext::LOCK_MUTEX) {
       mutex.lock();
     } else if (lockType == SSLContext::LOCK_SPINLOCK) {
       spinLock.lock();
+    } else if (lockType == SSLContext::LOCK_SHAREDMUTEX) {
+      if (read) {
+        sharedMutex.lock_shared();
+      } else {
+        sharedMutex.lock();
+      }
     }
     // lockType == LOCK_NONE, no-op
   }
 
-  void unlock() {
+  void unlock(bool read) {
     if (lockType == SSLContext::LOCK_MUTEX) {
       mutex.unlock();
     } else if (lockType == SSLContext::LOCK_SPINLOCK) {
       spinLock.unlock();
+    } else if (lockType == SSLContext::LOCK_SHAREDMUTEX) {
+      if (read) {
+        sharedMutex.unlock_shared();
+      } else {
+        sharedMutex.unlock();
+      }
     }
     // lockType == LOCK_NONE, no-op
   }
@@ -743,6 +756,7 @@ struct SSLLock {
   SSLContext::SSLLockType lockType;
   folly::SpinLock spinLock{};
   std::mutex mutex;
+  SharedMutex sharedMutex;
 };
 
 // Statics are unsafe in environments that call exit().
@@ -763,9 +777,9 @@ static std::map<int, SSLContext::SSLLockType>& lockTypes() {
 
 static void callbackLocking(int mode, int n, const char*, int) {
   if (mode & CRYPTO_LOCK) {
-    locks()[size_t(n)].lock();
+    locks()[size_t(n)].lock(mode & CRYPTO_READ);
   } else {
-    locks()[size_t(n)].unlock();
+    locks()[size_t(n)].unlock(mode & CRYPTO_READ);
   }
 }
 

folly/io/async/SSLContext.h

@@ -421,11 +421,7 @@ class SSLContext {
     return ctx_;
   }
 
-  enum SSLLockType {
-    LOCK_MUTEX,
-    LOCK_SPINLOCK,
-    LOCK_NONE
-  };
+  enum SSLLockType { LOCK_MUTEX, LOCK_SPINLOCK, LOCK_SHAREDMUTEX, LOCK_NONE };
 
   /**
    * Set preferences for how to treat locks in OpenSSL.  This must be