diff options
Diffstat (limited to 'abseil-cpp/absl/base/internal/thread_identity.h')
| -rw-r--r-- | abseil-cpp/absl/base/internal/thread_identity.h | 128 |
1 files changed, 69 insertions, 59 deletions
diff --git a/abseil-cpp/absl/base/internal/thread_identity.h b/abseil-cpp/absl/base/internal/thread_identity.h index ceb109b..b6e917c 100644 --- a/abseil-cpp/absl/base/internal/thread_identity.h +++ b/abseil-cpp/absl/base/internal/thread_identity.h @@ -32,6 +32,7 @@ #include "absl/base/config.h" #include "absl/base/internal/per_thread_tls.h" +#include "absl/base/optimization.h" namespace absl { ABSL_NAMESPACE_BEGIN @@ -61,38 +62,36 @@ struct PerThreadSynch { return reinterpret_cast<ThreadIdentity*>(this); } - PerThreadSynch *next; // Circular waiter queue; initialized to 0. - PerThreadSynch *skip; // If non-zero, all entries in Mutex queue + PerThreadSynch* next; // Circular waiter queue; initialized to 0. + PerThreadSynch* skip; // If non-zero, all entries in Mutex queue // up to and including "skip" have same // condition as this, and will be woken later bool may_skip; // if false while on mutex queue, a mutex unlocker // is using this PerThreadSynch as a terminator. Its // skip field must not be filled in because the loop // might then skip over the terminator. - - // The wait parameters of the current wait. waitp is null if the - // thread is not waiting. Transitions from null to non-null must - // occur before the enqueue commit point (state = kQueued in - // Enqueue() and CondVarEnqueue()). Transitions from non-null to - // null must occur after the wait is finished (state = kAvailable in - // Mutex::Block() and CondVar::WaitCommon()). This field may be - // changed only by the thread that describes this PerThreadSynch. A - // special case is Fer(), which calls Enqueue() on another thread, - // but with an identical SynchWaitParams pointer, thus leaving the - // pointer unchanged. - SynchWaitParams *waitp; - - bool suppress_fatal_errors; // If true, try to proceed even in the face of - // broken invariants. This is used within fatal - // signal handlers to improve the chances of - // debug logging information being output - // successfully. - - intptr_t readers; // Number of readers in mutex. - int priority; // Priority of thread (updated every so often). - - // When priority will next be read (cycles). - int64_t next_priority_read_cycles; + bool wake; // This thread is to be woken from a Mutex. + // If "x" is on a waiter list for a mutex, "x->cond_waiter" is true iff the + // waiter is waiting on the mutex as part of a CV Wait or Mutex Await. + // + // The value of "x->cond_waiter" is meaningless if "x" is not on a + // Mutex waiter list. + bool cond_waiter; + bool maybe_unlocking; // Valid at head of Mutex waiter queue; + // true if UnlockSlow could be searching + // for a waiter to wake. Used for an optimization + // in Enqueue(). true is always a valid value. + // Can be reset to false when the unlocker or any + // writer releases the lock, or a reader fully + // releases the lock. It may not be set to false + // by a reader that decrements the count to + // non-zero. protected by mutex spinlock + bool suppress_fatal_errors; // If true, try to proceed even in the face + // of broken invariants. This is used within + // fatal signal handlers to improve the + // chances of debug logging information being + // output successfully. + int priority; // Priority of thread (updated every so often). // State values: // kAvailable: This PerThreadSynch is available. @@ -105,36 +104,37 @@ struct PerThreadSynch { // // Transitions from kAvailable to kQueued require no barrier, they // are externally ordered by the Mutex. - enum State { - kAvailable, - kQueued - }; + enum State { kAvailable, kQueued }; std::atomic<State> state; - bool maybe_unlocking; // Valid at head of Mutex waiter queue; - // true if UnlockSlow could be searching - // for a waiter to wake. Used for an optimization - // in Enqueue(). true is always a valid value. - // Can be reset to false when the unlocker or any - // writer releases the lock, or a reader fully releases - // the lock. It may not be set to false by a reader - // that decrements the count to non-zero. - // protected by mutex spinlock + // The wait parameters of the current wait. waitp is null if the + // thread is not waiting. Transitions from null to non-null must + // occur before the enqueue commit point (state = kQueued in + // Enqueue() and CondVarEnqueue()). Transitions from non-null to + // null must occur after the wait is finished (state = kAvailable in + // Mutex::Block() and CondVar::WaitCommon()). This field may be + // changed only by the thread that describes this PerThreadSynch. A + // special case is Fer(), which calls Enqueue() on another thread, + // but with an identical SynchWaitParams pointer, thus leaving the + // pointer unchanged. + SynchWaitParams* waitp; - bool wake; // This thread is to be woken from a Mutex. + intptr_t readers; // Number of readers in mutex. - // If "x" is on a waiter list for a mutex, "x->cond_waiter" is true iff the - // waiter is waiting on the mutex as part of a CV Wait or Mutex Await. - // - // The value of "x->cond_waiter" is meaningless if "x" is not on a - // Mutex waiter list. - bool cond_waiter; + // When priority will next be read (cycles). + int64_t next_priority_read_cycles; // Locks held; used during deadlock detection. // Allocated in Synch_GetAllLocks() and freed in ReclaimThreadIdentity(). - SynchLocksHeld *all_locks; + SynchLocksHeld* all_locks; }; +// The instances of this class are allocated in NewThreadIdentity() with an +// alignment of PerThreadSynch::kAlignment. +// +// NOTE: The layout of fields in this structure is critical, please do not +// add, remove, or modify the field placements without fully auditing the +// layout. struct ThreadIdentity { // Must be the first member. The Mutex implementation requires that // the PerThreadSynch object associated with each thread is @@ -144,7 +144,7 @@ struct ThreadIdentity { // Private: Reserved for absl::synchronization_internal::Waiter. struct WaiterState { - char data[128]; + alignas(void*) char data[256]; } waiter_state; // Used by PerThreadSem::{Get,Set}ThreadBlockedCounter(). @@ -167,7 +167,10 @@ struct ThreadIdentity { // // Does not malloc(*), and is async-signal safe. // [*] Technically pthread_setspecific() does malloc on first use; however this -// is handled internally within tcmalloc's initialization already. +// is handled internally within tcmalloc's initialization already. Note that +// darwin does *not* use tcmalloc, so this can catch you if using MallocHooks +// on Apple platforms. Whatever function is calling your MallocHooks will need +// to watch for recursion on Apple platforms. // // New ThreadIdentity objects can be constructed and associated with a thread // by calling GetOrCreateCurrentThreadIdentity() in per-thread-sem.h. @@ -189,29 +192,31 @@ void ClearCurrentThreadIdentity(); // May be chosen at compile time via: -DABSL_FORCE_THREAD_IDENTITY_MODE=<mode // index> #ifdef ABSL_THREAD_IDENTITY_MODE_USE_POSIX_SETSPECIFIC -#error ABSL_THREAD_IDENTITY_MODE_USE_POSIX_SETSPECIFIC cannot be direcly set +#error ABSL_THREAD_IDENTITY_MODE_USE_POSIX_SETSPECIFIC cannot be directly set #else #define ABSL_THREAD_IDENTITY_MODE_USE_POSIX_SETSPECIFIC 0 #endif #ifdef ABSL_THREAD_IDENTITY_MODE_USE_TLS -#error ABSL_THREAD_IDENTITY_MODE_USE_TLS cannot be direcly set +#error ABSL_THREAD_IDENTITY_MODE_USE_TLS cannot be directly set #else #define ABSL_THREAD_IDENTITY_MODE_USE_TLS 1 #endif #ifdef ABSL_THREAD_IDENTITY_MODE_USE_CPP11 -#error ABSL_THREAD_IDENTITY_MODE_USE_CPP11 cannot be direcly set +#error ABSL_THREAD_IDENTITY_MODE_USE_CPP11 cannot be directly set #else #define ABSL_THREAD_IDENTITY_MODE_USE_CPP11 2 #endif #ifdef ABSL_THREAD_IDENTITY_MODE -#error ABSL_THREAD_IDENTITY_MODE cannot be direcly set +#error ABSL_THREAD_IDENTITY_MODE cannot be directly set #elif defined(ABSL_FORCE_THREAD_IDENTITY_MODE) #define ABSL_THREAD_IDENTITY_MODE ABSL_FORCE_THREAD_IDENTITY_MODE #elif defined(_WIN32) && !defined(__MINGW32__) #define ABSL_THREAD_IDENTITY_MODE ABSL_THREAD_IDENTITY_MODE_USE_CPP11 +#elif defined(__APPLE__) && defined(ABSL_HAVE_THREAD_LOCAL) +#define ABSL_THREAD_IDENTITY_MODE ABSL_THREAD_IDENTITY_MODE_USE_CPP11 #elif ABSL_PER_THREAD_TLS && defined(__GOOGLE_GRTE_VERSION__) && \ (__GOOGLE_GRTE_VERSION__ >= 20140228L) // Support for async-safe TLS was specifically added in GRTEv4. It's not @@ -235,13 +240,18 @@ ABSL_CONST_INIT extern thread_local ThreadIdentity* thread_identity_ptr; #error Thread-local storage not detected on this platform #endif -// thread_local variables cannot be in headers exposed by DLLs. However, it is -// important for performance reasons in general that -// `CurrentThreadIdentityIfPresent` be inlined. This is not possible across a -// DLL boundary so, with DLLs, we opt to have the function not be inlined. Note +// thread_local variables cannot be in headers exposed by DLLs or in certain +// build configurations on Apple platforms. However, it is important for +// performance reasons in general that `CurrentThreadIdentityIfPresent` be +// inlined. In the other cases we opt to have the function not be inlined. Note // that `CurrentThreadIdentityIfPresent` is declared above so we can exclude -// this entire inline definition when compiling as a DLL. -#if !defined(ABSL_BUILD_DLL) && !defined(ABSL_CONSUME_DLL) +// this entire inline definition. +#if !defined(__APPLE__) && !defined(ABSL_BUILD_DLL) && \ + !defined(ABSL_CONSUME_DLL) +#define ABSL_INTERNAL_INLINE_CURRENT_THREAD_IDENTITY_IF_PRESENT 1 +#endif + +#ifdef ABSL_INTERNAL_INLINE_CURRENT_THREAD_IDENTITY_IF_PRESENT inline ThreadIdentity* CurrentThreadIdentityIfPresent() { return thread_identity_ptr; } |