Repo created

TMessagesProj/jni/voip/webrtc/absl/synchronization/internal/sem_waiter.cc

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+// Copyright 2023 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "absl/synchronization/internal/sem_waiter.h"
+
+#ifdef ABSL_INTERNAL_HAVE_SEM_WAITER
+
+#include <semaphore.h>
+
+#include <atomic>
+#include <cassert>
+#include <cstdint>
+#include <cerrno>
+
+#include "absl/base/config.h"
+#include "absl/base/internal/raw_logging.h"
+#include "absl/base/internal/thread_identity.h"
+#include "absl/base/optimization.h"
+#include "absl/synchronization/internal/kernel_timeout.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace synchronization_internal {
+
+#ifdef ABSL_INTERNAL_NEED_REDUNDANT_CONSTEXPR_DECL
+constexpr char SemWaiter::kName[];
+#endif
+
+SemWaiter::SemWaiter() : wakeups_(0) {
+  if (sem_init(&sem_, 0, 0) != 0) {
+    ABSL_RAW_LOG(FATAL, "sem_init failed with errno %d\n", errno);
+  }
+}
+
+#if defined(__GLIBC__) && \
+    (__GLIBC__ > 2 || (__GLIBC__ == 2 && __GLIBC_MINOR__ >= 30))
+#define ABSL_INTERNAL_HAVE_SEM_CLOCKWAIT 1
+#elif defined(__ANDROID_API__) && __ANDROID_API__ >= 30
+#define ABSL_INTERNAL_HAVE_SEM_CLOCKWAIT 1
+#endif
+
+// Calls sem_timedwait() or possibly something else like
+// sem_clockwait() depending on the platform and
+// KernelTimeout requested. The return value is the same as a call to the return
+// value to a call to sem_timedwait().
+int SemWaiter::TimedWait(KernelTimeout t) {
+  if (KernelTimeout::SupportsSteadyClock() && t.is_relative_timeout()) {
+#if defined(ABSL_INTERNAL_HAVE_SEM_CLOCKWAIT) && defined(CLOCK_MONOTONIC)
+    const auto abs_clock_timeout = t.MakeClockAbsoluteTimespec(CLOCK_MONOTONIC);
+    return sem_clockwait(&sem_, CLOCK_MONOTONIC, &abs_clock_timeout);
+#endif
+  }
+
+  const auto abs_timeout = t.MakeAbsTimespec();
+  return sem_timedwait(&sem_, &abs_timeout);
+}
+
+bool SemWaiter::Wait(KernelTimeout t) {
+  // Loop until we timeout or consume a wakeup.
+  // Note that, since the thread ticker is just reset, we don't need to check
+  // whether the thread is idle on the very first pass of the loop.
+  bool first_pass = true;
+  while (true) {
+    int x = wakeups_.load(std::memory_order_relaxed);
+    while (x != 0) {
+      if (!wakeups_.compare_exchange_weak(x, x - 1,
+                                          std::memory_order_acquire,
+                                          std::memory_order_relaxed)) {
+        continue;  // Raced with someone, retry.
+      }
+      // Successfully consumed a wakeup, we're done.
+      return true;
+    }
+
+    if (!first_pass) MaybeBecomeIdle();
+    // Nothing to consume, wait (looping on EINTR).
+    while (true) {
+      if (!t.has_timeout()) {
+        if (sem_wait(&sem_) == 0) break;
+        if (errno == EINTR) continue;
+        ABSL_RAW_LOG(FATAL, "sem_wait failed: %d", errno);
+      } else {
+        if (TimedWait(t) == 0) break;
+        if (errno == EINTR) continue;
+        if (errno == ETIMEDOUT) return false;
+        ABSL_RAW_LOG(FATAL, "SemWaiter::TimedWait() failed: %d", errno);
+      }
+    }
+    first_pass = false;
+  }
+}
+
+void SemWaiter::Post() {
+  // Post a wakeup.
+  if (wakeups_.fetch_add(1, std::memory_order_release) == 0) {
+    // We incremented from 0, need to wake a potential waiter.
+    Poke();
+  }
+}
+
+void SemWaiter::Poke() {
+  if (sem_post(&sem_) != 0) {  // Wake any semaphore waiter.
+    ABSL_RAW_LOG(FATAL, "sem_post failed with errno %d\n", errno);
+  }
+}
+
+}  // namespace synchronization_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ABSL_INTERNAL_HAVE_SEM_WAITER