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authorGravatar Abseil Team <absl-team@google.com>2020-05-14 16:04:20 -0700
committerGravatar Andy Getz <durandal@google.com>2020-05-14 20:49:06 -0400
commitd118d4bb115387cc52c5338221f2554a940e6d90 (patch)
tree0577459d15af3035aa51ee3869b72f6b1c4ea5a1 /absl/base
parentf2bc9d11e841e247c95f9f1426b367721d0a8fa6 (diff)
Export of internal Abseil changes
-- b8e6b64b604449bb51ed0ba8e9439097f3aa8773 by Abseil Team <absl-team@google.com>: fix typo 'implentation' -> 'implementation' PiperOrigin-RevId: 311623471 -- 2b9262a311f3329c8006835a79498edd90568acd by Matt Kulukundis <kfm@google.com>: Internal cleanup PiperOrigin-RevId: 311549039 -- 7507ed3c28113e28f993aa634bd44a9a0d4c4a2c by Derek Mauro <dmauro@google.com>: Delete LinkerInitialized Now that all SpinLocks have the same scheduling mode for their entire lives, the scheduling mode does not need to be re-tested in the loop in LockSlow. PiperOrigin-RevId: 311521474 -- abf5fae67e21b38cda4083aaafd7012e2c6fbb7d by Andy Getzendanner <durandal@google.com>: Fix public target name of the random library Import of https://github.com/abseil/abseil-cpp/pull/684 PiperOrigin-RevId: 311429555 GitOrigin-RevId: b8e6b64b604449bb51ed0ba8e9439097f3aa8773 Change-Id: Ic48f671846bda059cc46f4a0b967cc3b1a733ba0
Diffstat (limited to 'absl/base')
-rw-r--r--absl/base/internal/spinlock.cc37
-rw-r--r--absl/base/internal/spinlock.h19
-rw-r--r--absl/base/macros.h30
3 files changed, 8 insertions, 78 deletions
diff --git a/absl/base/internal/spinlock.cc b/absl/base/internal/spinlock.cc
index 7cac72f9..a7d44f3e 100644
--- a/absl/base/internal/spinlock.cc
+++ b/absl/base/internal/spinlock.cc
@@ -79,29 +79,6 @@ SpinLock::SpinLock(base_internal::SchedulingMode mode)
ABSL_TSAN_MUTEX_CREATE(this, __tsan_mutex_not_static);
}
-SpinLock::SpinLock(base_internal::LinkerInitialized,
- base_internal::SchedulingMode mode) {
- ABSL_TSAN_MUTEX_CREATE(this, 0);
- if (IsCooperative(mode)) {
- InitLinkerInitializedAndCooperative();
- }
- // Otherwise, lockword_ is already initialized.
-}
-
-// Static (linker initialized) spinlocks always start life as functional
-// non-cooperative locks. When their static constructor does run, it will call
-// this initializer to augment the lockword with the cooperative bit. By
-// actually taking the lock when we do this we avoid the need for an atomic
-// operation in the regular unlock path.
-//
-// SlowLock() must be careful to re-test for this bit so that any outstanding
-// waiters may be upgraded to cooperative status.
-void SpinLock::InitLinkerInitializedAndCooperative() {
- Lock();
- lockword_.fetch_or(kSpinLockCooperative, std::memory_order_relaxed);
- Unlock();
-}
-
// Monitor the lock to see if its value changes within some time period
// (adaptive_spin_count loop iterations). The last value read from the lock
// is returned from the method.
@@ -128,6 +105,14 @@ void SpinLock::SlowLock() {
if ((lock_value & kSpinLockHeld) == 0) {
return;
}
+
+ base_internal::SchedulingMode scheduling_mode;
+ if ((lock_value & kSpinLockCooperative) != 0) {
+ scheduling_mode = base_internal::SCHEDULE_COOPERATIVE_AND_KERNEL;
+ } else {
+ scheduling_mode = base_internal::SCHEDULE_KERNEL_ONLY;
+ }
+
// The lock was not obtained initially, so this thread needs to wait for
// it. Record the current timestamp in the local variable wait_start_time
// so the total wait time can be stored in the lockword once this thread
@@ -158,12 +143,6 @@ void SpinLock::SlowLock() {
}
}
- base_internal::SchedulingMode scheduling_mode;
- if ((lock_value & kSpinLockCooperative) != 0) {
- scheduling_mode = base_internal::SCHEDULE_COOPERATIVE_AND_KERNEL;
- } else {
- scheduling_mode = base_internal::SCHEDULE_KERNEL_ONLY;
- }
// SpinLockDelay() calls into fiber scheduler, we need to see
// synchronization there to avoid false positives.
ABSL_TSAN_MUTEX_PRE_DIVERT(this, 0);
diff --git a/absl/base/internal/spinlock.h b/absl/base/internal/spinlock.h
index 2b08a2d6..2222398b 100644
--- a/absl/base/internal/spinlock.h
+++ b/absl/base/internal/spinlock.h
@@ -56,27 +56,9 @@ class ABSL_LOCKABLE SpinLock {
ABSL_TSAN_MUTEX_CREATE(this, __tsan_mutex_not_static);
}
- // Special constructor for use with static SpinLock objects. E.g.,
- //
- // static SpinLock lock(base_internal::kLinkerInitialized);
- //
- // When initialized using this constructor, we depend on the fact
- // that the linker has already initialized the memory appropriately. The lock
- // is initialized in non-cooperative mode.
- //
- // A SpinLock constructed like this can be freely used from global
- // initializers without worrying about the order in which global
- // initializers run.
- explicit SpinLock(base_internal::LinkerInitialized) {
- // Does nothing; lockword_ is already initialized
- ABSL_TSAN_MUTEX_CREATE(this, 0);
- }
-
// Constructors that allow non-cooperative spinlocks to be created for use
// inside thread schedulers. Normal clients should not use these.
explicit SpinLock(base_internal::SchedulingMode mode);
- SpinLock(base_internal::LinkerInitialized,
- base_internal::SchedulingMode mode);
// Constructor for global SpinLock instances. See absl/base/const_init.h.
constexpr SpinLock(absl::ConstInitType, base_internal::SchedulingMode mode)
@@ -168,7 +150,6 @@ class ABSL_LOCKABLE SpinLock {
}
uint32_t TryLockInternal(uint32_t lock_value, uint32_t wait_cycles);
- void InitLinkerInitializedAndCooperative();
void SlowLock() ABSL_ATTRIBUTE_COLD;
void SlowUnlock(uint32_t lock_value) ABSL_ATTRIBUTE_COLD;
uint32_t SpinLoop();
diff --git a/absl/base/macros.h b/absl/base/macros.h
index 2c4e3570..ea1da65b 100644
--- a/absl/base/macros.h
+++ b/absl/base/macros.h
@@ -55,36 +55,6 @@ auto ArraySizeHelper(const T (&array)[N]) -> char (&)[N];
ABSL_NAMESPACE_END
} // namespace absl
-// kLinkerInitialized
-//
-// An enum used only as a constructor argument to indicate that a variable has
-// static storage duration, and that the constructor should do nothing to its
-// state. Use of this macro indicates to the reader that it is legal to
-// declare a static instance of the class, provided the constructor is given
-// the absl::base_internal::kLinkerInitialized argument.
-//
-// Normally, it is unsafe to declare a static variable that has a constructor or
-// a destructor because invocation order is undefined. However, if the type can
-// be zero-initialized (which the loader does for static variables) into a valid
-// state and the type's destructor does not affect storage, then a constructor
-// for static initialization can be declared.
-//
-// Example:
-// // Declaration
-// explicit MyClass(absl::base_internal:LinkerInitialized x) {}
-//
-// // Invocation
-// static MyClass my_global(absl::base_internal::kLinkerInitialized);
-namespace absl {
-ABSL_NAMESPACE_BEGIN
-namespace base_internal {
-enum LinkerInitialized {
- kLinkerInitialized = 0,
-};
-} // namespace base_internal
-ABSL_NAMESPACE_END
-} // namespace absl
-
// ABSL_FALLTHROUGH_INTENDED
//
// Annotates implicit fall-through between switch labels, allowing a case to