Modernize SkMutex and SkSemaphore.
- use <atomic>
- fuse SkMutex and SkBaseMutex
- fuse SkSemaphore and SkBaseSemaphore
Still TODO:
- replace SK_DECLARE_STATIC_MUTEX(name) with static SkMutex name
I just didn't want to bother fixing all that up until I know this CL sticks.
BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1947153002
No public API changes.
TBR=reed@google.com
Review-Url: https://codereview.chromium.org/1947153002
diff --git a/include/core/SkPixelRef.h b/include/core/SkPixelRef.h
index 90e0de5..d836b2f 100644
--- a/include/core/SkPixelRef.h
+++ b/include/core/SkPixelRef.h
@@ -342,7 +342,7 @@
/** Return the mutex associated with this pixelref. This value is assigned
in the constructor, and cannot change during the lifetime of the object.
*/
- SkBaseMutex* mutex() const { return &fMutex; }
+ SkMutex* mutex() const { return &fMutex; }
// only call from constructor. Flags this to always be locked, removing
// the need to grab the mutex and call onLockPixels/onUnlockPixels.
diff --git a/include/ports/SkFontConfigInterface.h b/include/ports/SkFontConfigInterface.h
index 72cad0a..9f98e35 100644
--- a/include/ports/SkFontConfigInterface.h
+++ b/include/ports/SkFontConfigInterface.h
@@ -13,7 +13,6 @@
#include "SkRefCnt.h"
#include "SkTypeface.h"
-struct SkBaseMutex;
class SkFontMgr;
/**
diff --git a/include/private/SkMutex.h b/include/private/SkMutex.h
index 8c78e12..b9af00f 100644
--- a/include/private/SkMutex.h
+++ b/include/private/SkMutex.h
@@ -8,33 +8,20 @@
#ifndef SkMutex_DEFINED
#define SkMutex_DEFINED
-// This file is not part of the public Skia API.
#include "../private/SkSemaphore.h"
+#include "../private/SkThreadID.h"
#include "SkTypes.h"
-#ifdef SK_DEBUG
- #include "../private/SkThreadID.h"
-#endif
+// TODO: no need for this anymore.
+#define SK_DECLARE_STATIC_MUTEX(name) static SkMutex name;
-#define SK_MUTEX_SEMAPHORE_INIT {1, {0}}
+class SkMutex {
+public:
+ constexpr SkMutex() = default;
-#ifdef SK_DEBUG
- #define SK_BASE_MUTEX_INIT {SK_MUTEX_SEMAPHORE_INIT, 0}
-#else
- #define SK_BASE_MUTEX_INIT {SK_MUTEX_SEMAPHORE_INIT}
-#endif
+ SkMutex(const SkMutex&) = delete;
+ SkMutex& operator=(const SkMutex&) = delete;
-// Using POD-style initialization prevents the generation of a static initializer.
-//
-// Without magic statics there are no thread safety guarantees on initialization
-// of local statics (even POD). As a result, it is illegal to use
-// SK_DECLARE_STATIC_MUTEX in a function.
-//
-// Because SkBaseMutex is not a primitive, a static SkBaseMutex cannot be
-// initialized in a class with this macro.
-#define SK_DECLARE_STATIC_MUTEX(name) namespace {} static SkBaseMutex name = SK_BASE_MUTEX_INIT;
-
-struct SkBaseMutex {
void acquire() {
fSemaphore.wait();
SkDEBUGCODE(fOwner = SkGetThreadID();)
@@ -50,20 +37,9 @@
SkASSERT(fOwner == SkGetThreadID());
}
- SkBaseSemaphore fSemaphore;
- SkDEBUGCODE(SkThreadID fOwner;)
-};
-
-// This needs to use subclassing instead of encapsulation to make SkAutoMutexAcquire to work.
-class SkMutex : public SkBaseMutex {
-public:
- SkMutex () {
- fSemaphore = SK_MUTEX_SEMAPHORE_INIT;
- SkDEBUGCODE(fOwner = kIllegalThreadID);
- }
- ~SkMutex () { fSemaphore.deleteSemaphore(); }
- SkMutex(const SkMutex&) = delete;
- SkMutex& operator=(const SkMutex&) = delete;
+private:
+ SkSemaphore fSemaphore{1};
+ SkDEBUGCODE(SkThreadID fOwner{kIllegalThreadID};)
};
template <typename Lock>
@@ -116,10 +92,10 @@
Lock &fLock;
};
-typedef SkAutoTAcquire<SkBaseMutex> SkAutoMutexAcquire;
+typedef SkAutoTAcquire<SkMutex> SkAutoMutexAcquire;
#define SkAutoMutexAcquire(...) SK_REQUIRE_LOCAL_VAR(SkAutoMutexAcquire)
-typedef SkAutoTExclusive<SkBaseMutex> SkAutoMutexExclusive;
+typedef SkAutoTExclusive<SkMutex> SkAutoMutexExclusive;
#define SkAutoMutexExclusive(...) SK_REQUIRE_LOCAL_VAR(SkAutoMutexExclusive)
#endif//SkMutex_DEFINED
diff --git a/include/private/SkSemaphore.h b/include/private/SkSemaphore.h
index cb2f58d..adee574 100644
--- a/include/private/SkSemaphore.h
+++ b/include/private/SkSemaphore.h
@@ -8,43 +8,26 @@
#ifndef SkSemaphore_DEFINED
#define SkSemaphore_DEFINED
+#include "../private/SkOnce.h"
#include "SkTypes.h"
-#include "../private/SkAtomics.h"
-#include "../private/SkOncePtr.h"
+#include <atomic>
-struct SkBaseSemaphore {
+class SkSemaphore {
+public:
+ constexpr SkSemaphore(int count = 0)
+ : fCount(count), fOSSemaphore(nullptr) {}
- // Increment the counter by 1.
- // This is a specialization for supporting SkMutex.
- void signal() {
- // Since this fetches the value before the add, 0 indicates that this thread is running and
- // no threads are waiting, -1 and below means that threads are waiting, but only signal 1
- // thread to run.
- if (sk_atomic_fetch_add(&fCount, 1, sk_memory_order_release) < 0) {
- this->osSignal(1);
- }
- }
+ ~SkSemaphore();
- // Increment the counter N times.
- // Generally it's better to call signal(N) instead of signal() N times.
- void signal(int N);
+ // Increment the counter n times.
+ // Generally it's better to call signal(n) instead of signal() n times.
+ void signal(int n = 1);
// Decrement the counter by 1,
// then if the counter is <= 0, sleep this thread until the counter is > 0.
- void wait() {
- // Since this fetches the value before the subtract, zero and below means that there are no
- // resources left, so the thread needs to wait.
- if (sk_atomic_fetch_sub(&fCount, 1, sk_memory_order_acquire) <= 0) {
- this->osWait();
- }
- }
+ void wait();
- struct OSSemaphore;
-
- void osSignal(int n);
- void osWait();
- void deleteSemaphore();
-
+private:
// This implementation follows the general strategy of
// 'A Lightweight Semaphore with Partial Spinning'
// found here
@@ -54,33 +37,40 @@
// We wrap an OS-provided semaphore with a user-space atomic counter that
// lets us avoid interacting with the OS semaphore unless strictly required:
// moving the count from >0 to <=0 or vice-versa, i.e. sleeping or waking threads.
- int fCount;
- SkBaseOncePtr<OSSemaphore> fOSSemaphore;
+ struct OSSemaphore;
+
+ void osSignal(int n);
+ void osWait();
+
+ std::atomic<int> fCount;
+ SkOnce fOSSemaphoreOnce;
+ OSSemaphore* fOSSemaphore;
};
-/**
- * SkSemaphore is a fast mostly-user-space semaphore.
- *
- * A semaphore is logically an atomic integer with a few special properties:
- * - The integer always starts at 0.
- * - You can only increment or decrement it, never read or write it.
- * - Increment is spelled 'signal()'; decrement is spelled 'wait()'.
- * - If a call to wait() decrements the counter to <= 0,
- * the calling thread sleeps until another thread signal()s it back above 0.
- */
-class SkSemaphore : SkNoncopyable {
-public:
- // Initializes the counter to 0.
- // (Though all current implementations could start from an arbitrary value.)
- SkSemaphore();
- ~SkSemaphore();
+inline void SkSemaphore::signal(int n) {
+ int prev = fCount.fetch_add(n, std::memory_order_release);
- void wait();
+ // We only want to call the OS semaphore when our logical count crosses
+ // from <= 0 to >0 (when we need to wake sleeping threads).
+ //
+ // This is easiest to think about with specific examples of prev and n.
+ // If n == 5 and prev == -3, there are 3 threads sleeping and we signal
+ // SkTMin(-(-3), 5) == 3 times on the OS semaphore, leaving the count at 2.
+ //
+ // If prev >= 0, no threads are waiting, SkTMin(-prev, n) is always <= 0,
+ // so we don't call the OS semaphore, leaving the count at (prev + n).
+ int toSignal = SkTMin(-prev, n);
+ if (toSignal > 0) {
+ this->osSignal(toSignal);
+ }
+}
- void signal(int n = 1);
-
-private:
- SkBaseSemaphore fBaseSemaphore;
-};
+inline void SkSemaphore::wait() {
+ // Since this fetches the value before the subtract, zero and below means that there are no
+ // resources left, so the thread needs to wait.
+ if (fCount.fetch_sub(1, std::memory_order_acquire) <= 0) {
+ this->osWait();
+ }
+}
#endif//SkSemaphore_DEFINED
diff --git a/src/core/SkSemaphore.cpp b/src/core/SkSemaphore.cpp
index da422e2..0646b15 100644
--- a/src/core/SkSemaphore.cpp
+++ b/src/core/SkSemaphore.cpp
@@ -9,7 +9,7 @@
#if defined(SK_BUILD_FOR_MAC) || defined(SK_BUILD_FOR_IOS)
#include <mach/mach.h>
- struct SkBaseSemaphore::OSSemaphore {
+ struct SkSemaphore::OSSemaphore {
semaphore_t fSemaphore;
OSSemaphore() {
@@ -21,7 +21,7 @@
void wait() { semaphore_wait(fSemaphore); }
};
#elif defined(SK_BUILD_FOR_WIN32)
- struct SkBaseSemaphore::OSSemaphore {
+ struct SkSemaphore::OSSemaphore {
HANDLE fSemaphore;
OSSemaphore() {
@@ -41,7 +41,7 @@
// It's important we test for Mach before this. This code will compile but not work there.
#include <errno.h>
#include <semaphore.h>
- struct SkBaseSemaphore::OSSemaphore {
+ struct SkSemaphore::OSSemaphore {
sem_t fSemaphore;
OSSemaphore() { sem_init(&fSemaphore, 0/*cross process?*/, 0/*initial count*/); }
@@ -57,43 +57,16 @@
///////////////////////////////////////////////////////////////////////////////
-void SkBaseSemaphore::signal(int n) {
- SkASSERT(n >= 0);
-
- // We only want to call the OS semaphore when our logical count crosses
- // from <= 0 to >0 (when we need to wake sleeping threads).
- //
- // This is easiest to think about with specific examples of prev and n.
- // If n == 5 and prev == -3, there are 3 threads sleeping and we signal
- // SkTMin(-(-3), 5) == 3 times on the OS semaphore, leaving the count at 2.
- //
- // If prev >= 0, no threads are waiting, SkTMin(-prev, n) is always <= 0,
- // so we don't call the OS semaphore, leaving the count at (prev + n).
- int prev = sk_atomic_fetch_add(&fCount, n, sk_memory_order_release);
- int toSignal = SkTMin(-prev, n);
- if (toSignal > 0) {
- this->osSignal(toSignal);
- }
+void SkSemaphore::osSignal(int n) {
+ fOSSemaphoreOnce([this] { fOSSemaphore = new OSSemaphore; });
+ fOSSemaphore->signal(n);
}
-static SkBaseSemaphore::OSSemaphore* semaphore(SkBaseSemaphore* semaphore) {
- return semaphore->fOSSemaphore.get([](){ return new SkBaseSemaphore::OSSemaphore(); });
+void SkSemaphore::osWait() {
+ fOSSemaphoreOnce([this] { fOSSemaphore = new OSSemaphore; });
+ fOSSemaphore->wait();
}
-void SkBaseSemaphore::osSignal(int n) { semaphore(this)->signal(n); }
-
-void SkBaseSemaphore::osWait() { semaphore(this)->wait(); }
-
-void SkBaseSemaphore::deleteSemaphore() {
- delete (OSSemaphore*) fOSSemaphore;
+SkSemaphore::~SkSemaphore() {
+ delete fOSSemaphore;
}
-
-///////////////////////////////////////////////////////////////////////////////
-
-SkSemaphore::SkSemaphore(){ fBaseSemaphore = {0, {0}}; }
-
-SkSemaphore::~SkSemaphore() { fBaseSemaphore.deleteSemaphore(); }
-
-void SkSemaphore::wait() { fBaseSemaphore.wait(); }
-
-void SkSemaphore::signal(int n) {fBaseSemaphore.signal(n); }
diff --git a/src/lazy/SkDiscardableMemoryPool.cpp b/src/lazy/SkDiscardableMemoryPool.cpp
index 1f3bcf9..2be4c75 100644
--- a/src/lazy/SkDiscardableMemoryPool.cpp
+++ b/src/lazy/SkDiscardableMemoryPool.cpp
@@ -29,7 +29,7 @@
/**
* Without mutex, will be not be thread safe.
*/
- DiscardableMemoryPool(size_t budget, SkBaseMutex* mutex = nullptr);
+ DiscardableMemoryPool(size_t budget, SkMutex* mutex = nullptr);
virtual ~DiscardableMemoryPool();
SkDiscardableMemory* create(size_t bytes) override;
@@ -52,9 +52,9 @@
#endif // SK_LAZY_CACHE_STATS
private:
- SkBaseMutex* fMutex;
- size_t fBudget;
- size_t fUsed;
+ SkMutex* fMutex;
+ size_t fBudget;
+ size_t fUsed;
SkTInternalLList<PoolDiscardableMemory> fList;
/** Function called to free memory if needed */
@@ -128,8 +128,7 @@
////////////////////////////////////////////////////////////////////////////////
-DiscardableMemoryPool::DiscardableMemoryPool(size_t budget,
- SkBaseMutex* mutex)
+DiscardableMemoryPool::DiscardableMemoryPool(size_t budget, SkMutex* mutex)
: fMutex(mutex)
, fBudget(budget)
, fUsed(0) {
@@ -241,7 +240,7 @@
} // namespace
-SkDiscardableMemoryPool* SkDiscardableMemoryPool::Create(size_t size, SkBaseMutex* mutex) {
+SkDiscardableMemoryPool* SkDiscardableMemoryPool::Create(size_t size, SkMutex* mutex) {
return new DiscardableMemoryPool(size, mutex);
}
diff --git a/src/lazy/SkDiscardableMemoryPool.h b/src/lazy/SkDiscardableMemoryPool.h
index 92ba48b..ad8d796 100644
--- a/src/lazy/SkDiscardableMemoryPool.h
+++ b/src/lazy/SkDiscardableMemoryPool.h
@@ -52,8 +52,7 @@
* the pool works.
* Without mutex, will be not be thread safe.
*/
- static SkDiscardableMemoryPool* Create(
- size_t size, SkBaseMutex* mutex = nullptr);
+ static SkDiscardableMemoryPool* Create(size_t size, SkMutex* mutex = nullptr);
};
/**