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Unified Diff: base/threading/thread_local_storage.h

Issue 60743004: Implement chromium's TLS. (Closed) Base URL: https://chromium.googlesource.com/chromium/src.git@master
Patch Set: sync and reland Created 6 years, 11 months ago
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Index: base/threading/thread_local_storage.h
diff --git a/base/threading/thread_local_storage.h b/base/threading/thread_local_storage.h
index eb5648f76c9b693a6ac041d5b6a41ee35a1fcad9..53ebe55e51ce4308874894b53cbc15b95dae6a7a 100644
--- a/base/threading/thread_local_storage.h
+++ b/base/threading/thread_local_storage.h
@@ -8,12 +8,71 @@
#include "base/base_export.h"
#include "base/basictypes.h"
-#if defined(OS_POSIX)
+#if defined(OS_WIN)
+#include <windows.h>
+#elif defined(OS_POSIX)
#include <pthread.h>
#endif
namespace base {
+namespace internal {
+
+// WARNING: You should *NOT* be using this class directly.
+// PlatformThreadLocalStorage is low-level abstraction to the OS's TLS
+// interface, you should instead be using ThreadLocalStorage::StaticSlot/Slot.
+class BASE_EXPORT PlatformThreadLocalStorage {
+ public:
+
+#if defined(OS_WIN)
+ typedef unsigned long TLSKey;
+ enum { TLS_KEY_OUT_OF_INDEXES = TLS_OUT_OF_INDEXES };
+#elif defined(OS_POSIX)
+ typedef pthread_key_t TLSKey;
+ // The following is a "reserved key" which is used in our generic Chromium
+ // ThreadLocalStorage implementation. We expect that an OS will not return
+ // such a key, but if it is returned (i.e., the OS tries to allocate it) we
+ // will just request another key.
+ enum { TLS_KEY_OUT_OF_INDEXES = 0x7FFFFFFF };
+#endif
+
+ // The following methods need to be supported on each OS platform, so that
+ // the Chromium ThreadLocalStore functionality can be constructed.
+ // Chromium will use these methods to acquire a single OS slot, and then use
+ // that to support a much larger number of Chromium slots (independent of the
+ // OS restrictions).
+ // The following returns true if it successfully is able to return an OS
+ // key in |key|.
+ static bool AllocTLS(TLSKey* key);
+ // Note: FreeTLS() doesn't have to be called, it is fine with this leak, OS
+ // might not reuse released slot, you might just reset the TLS value with
+ // SetTLSValue().
+ static void FreeTLS(TLSKey key);
+ static void SetTLSValue(TLSKey key, void* value);
+ static void* GetTLSValue(TLSKey key);
+
+ // Each platform (OS implementation) is required to call this method on each
+ // terminating thread when the thread is about to terminate. This method
+ // will then call all registered destructors for slots in Chromium
+ // ThreadLocalStorage, until there are no slot values remaining as having
+ // been set on this thread.
+ // Destructors may end up being called multiple times on a terminating
+ // thread, as other destructors may re-set slots that were previously
+ // destroyed.
+#if defined(OS_WIN)
+ // Since Windows which doesn't support TLS destructor, the implementation
+ // should use GetTLSValue() to retrieve the value of TLS slot.
+ static void OnThreadExit();
+#elif defined(OS_POSIX)
+ // |Value| is the data stored in TLS slot, The implementation can't use
+ // GetTLSValue() to retrieve the value of slot as it has already been reset
+ // in Posix.
+ static void OnThreadExit(void* value);
+#endif
+};
+
+} // namespace internal
+
// Wrapper for thread local storage. This class doesn't do much except provide
// an API for portability.
class BASE_EXPORT ThreadLocalStorage {
@@ -60,12 +119,7 @@ class BASE_EXPORT ThreadLocalStorage {
// The internals of this struct should be considered private.
bool initialized_;
-#if defined(OS_WIN)
int slot_;
-#elif defined(OS_POSIX)
- pthread_key_t key_;
-#endif
-
};
// A convenience wrapper around StaticSlot with a constructor. Can be used
@@ -77,11 +131,8 @@ class BASE_EXPORT ThreadLocalStorage {
private:
using StaticSlot::initialized_;
-#if defined(OS_WIN)
using StaticSlot::slot_;
-#elif defined(OS_POSIX)
- using StaticSlot::key_;
-#endif
+
DISALLOW_COPY_AND_ASSIGN(Slot);
};
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