thodg/libgit2/src/util/thread.h

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• Hash : c3b7ace9
  Author :
  Date : 2021-11-14T16:43:53
  

  refactor: make util an object library Instead of simply including the utility files directly, make them a cmake object library for easy reusability between other projects within libgit2. Now the top-level `src` is responsible for platform selection, while the next-level `libgit2` and `util` configurations are responsible for identifying what objects they include.

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• src/util/thread.h

• /*
   * Copyright (C) the libgit2 contributors. All rights reserved.
   *
   * This file is part of libgit2, distributed under the GNU GPL v2 with
   * a Linking Exception. For full terms see the included COPYING file.
   */
  #ifndef INCLUDE_thread_h__
  #define INCLUDE_thread_h__
  
  #if defined(GIT_THREADS)
  
  #if defined(__clang__)
  
  # if (__clang_major__ < 3 || (__clang_major__ == 3 && __clang_minor__ < 1))
  #  error Atomic primitives do not exist on this version of clang; configure libgit2 with -DUSE_THREADS=OFF
  # else
  #  define GIT_BUILTIN_ATOMIC
  # endif
  
  #elif defined(__GNUC__)
  
  # if (__GNUC__ < 4 || (__GNUC__ == 4 && __GNUC_MINOR__ < 1))
  #  error Atomic primitives do not exist on this version of gcc; configure libgit2 with -DUSE_THREADS=OFF
  # elif (__GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 7))
  #  define GIT_BUILTIN_ATOMIC
  # else
  #  define GIT_BUILTIN_SYNC
  # endif
  
  #endif
  
  #endif /* GIT_THREADS */
  
  /* Common operations even if threading has been disabled */
  typedef struct {
  #if defined(GIT_WIN32)
  	volatile long val;
  #else
  	volatile int val;
  #endif
  } git_atomic32;
  
  #ifdef GIT_ARCH_64
  
  typedef struct {
  #if defined(GIT_WIN32)
  	volatile __int64 val;
  #else
  	volatile int64_t val;
  #endif
  } git_atomic64;
  
  typedef git_atomic64 git_atomic_ssize;
  
  #define git_atomic_ssize_set git_atomic64_set
  #define git_atomic_ssize_add git_atomic64_add
  #define git_atomic_ssize_get git_atomic64_get
  
  #else
  
  typedef git_atomic32 git_atomic_ssize;
  
  #define git_atomic_ssize_set git_atomic32_set
  #define git_atomic_ssize_add git_atomic32_add
  #define git_atomic_ssize_get git_atomic32_get
  
  #endif
  
  #ifdef GIT_THREADS
  
  #ifdef GIT_WIN32
  #   include "win32/thread.h"
  #else
  #   include "unix/pthread.h"
  #endif
  
  /*
   * Atomically sets the contents of *a to be val.
   */
  GIT_INLINE(void) git_atomic32_set(git_atomic32 *a, int val)
  {
  #if defined(GIT_WIN32)
  	InterlockedExchange(&a->val, (LONG)val);
  #elif defined(GIT_BUILTIN_ATOMIC)
  	__atomic_store_n(&a->val, val, __ATOMIC_SEQ_CST);
  #elif defined(GIT_BUILTIN_SYNC)
  	__sync_lock_test_and_set(&a->val, val);
  #else
  #	error "Unsupported architecture for atomic operations"
  #endif
  }
  
  /*
   * Atomically increments the contents of *a by 1, and stores the result back into *a.
   * @return the result of the operation.
   */
  GIT_INLINE(int) git_atomic32_inc(git_atomic32 *a)
  {
  #if defined(GIT_WIN32)
  	return InterlockedIncrement(&a->val);
  #elif defined(GIT_BUILTIN_ATOMIC)
  	return __atomic_add_fetch(&a->val, 1, __ATOMIC_SEQ_CST);
  #elif defined(GIT_BUILTIN_SYNC)
  	return __sync_add_and_fetch(&a->val, 1);
  #else
  #	error "Unsupported architecture for atomic operations"
  #endif
  }
  
  /*
   * Atomically adds the contents of *a and addend, and stores the result back into *a.
   * @return the result of the operation.
   */
  GIT_INLINE(int) git_atomic32_add(git_atomic32 *a, int32_t addend)
  {
  #if defined(GIT_WIN32)
  	return InterlockedAdd(&a->val, addend);
  #elif defined(GIT_BUILTIN_ATOMIC)
  	return __atomic_add_fetch(&a->val, addend, __ATOMIC_SEQ_CST);
  #elif defined(GIT_BUILTIN_SYNC)
  	return __sync_add_and_fetch(&a->val, addend);
  #else
  #	error "Unsupported architecture for atomic operations"
  #endif
  }
  
  /*
   * Atomically decrements the contents of *a by 1, and stores the result back into *a.
   * @return the result of the operation.
   */
  GIT_INLINE(int) git_atomic32_dec(git_atomic32 *a)
  {
  #if defined(GIT_WIN32)
  	return InterlockedDecrement(&a->val);
  #elif defined(GIT_BUILTIN_ATOMIC)
  	return __atomic_sub_fetch(&a->val, 1, __ATOMIC_SEQ_CST);
  #elif defined(GIT_BUILTIN_SYNC)
  	return __sync_sub_and_fetch(&a->val, 1);
  #else
  #	error "Unsupported architecture for atomic operations"
  #endif
  }
  
  /*
   * Atomically gets the contents of *a.
   * @return the contents of *a.
   */
  GIT_INLINE(int) git_atomic32_get(git_atomic32 *a)
  {
  #if defined(GIT_WIN32)
  	return (int)InterlockedCompareExchange(&a->val, 0, 0);
  #elif defined(GIT_BUILTIN_ATOMIC)
  	return __atomic_load_n(&a->val, __ATOMIC_SEQ_CST);
  #elif defined(GIT_BUILTIN_SYNC)
  	return __sync_val_compare_and_swap(&a->val, 0, 0);
  #else
  #	error "Unsupported architecture for atomic operations"
  #endif
  }
  
  GIT_INLINE(void *) git_atomic__compare_and_swap(
  	void * volatile *ptr, void *oldval, void *newval)
  {
  #if defined(GIT_WIN32)
  	return InterlockedCompareExchangePointer((volatile PVOID *)ptr, newval, oldval);
  #elif defined(GIT_BUILTIN_ATOMIC)
  	void *foundval = oldval;
  	__atomic_compare_exchange(ptr, &foundval, &newval, false, __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST);
  	return foundval;
  #elif defined(GIT_BUILTIN_SYNC)
  	return __sync_val_compare_and_swap(ptr, oldval, newval);
  #else
  #	error "Unsupported architecture for atomic operations"
  #endif
  }
  
  GIT_INLINE(volatile void *) git_atomic__swap(
  	void * volatile *ptr, void *newval)
  {
  #if defined(GIT_WIN32)
  	return InterlockedExchangePointer(ptr, newval);
  #elif defined(GIT_BUILTIN_ATOMIC)
  	void * foundval = NULL;
  	__atomic_exchange(ptr, &newval, &foundval, __ATOMIC_SEQ_CST);
  	return foundval;
  #elif defined(GIT_BUILTIN_SYNC)
  	return (volatile void *)__sync_lock_test_and_set(ptr, newval);
  #else
  #	error "Unsupported architecture for atomic operations"
  #endif
  }
  
  GIT_INLINE(volatile void *) git_atomic__load(void * volatile *ptr)
  {
  #if defined(GIT_WIN32)
  	void *newval = NULL, *oldval = NULL;
  	return (volatile void *)InterlockedCompareExchangePointer((volatile PVOID *)ptr, newval, oldval);
  #elif defined(GIT_BUILTIN_ATOMIC)
  	return (volatile void *)__atomic_load_n(ptr, __ATOMIC_SEQ_CST);
  #elif defined(GIT_BUILTIN_SYNC)
  	return (volatile void *)__sync_val_compare_and_swap(ptr, 0, 0);
  #else
  #	error "Unsupported architecture for atomic operations"
  #endif
  }
  
  #ifdef GIT_ARCH_64
  
  /*
   * Atomically adds the contents of *a and addend, and stores the result back into *a.
   * @return the result of the operation.
   */
  GIT_INLINE(int64_t) git_atomic64_add(git_atomic64 *a, int64_t addend)
  {
  #if defined(GIT_WIN32)
  	return InterlockedAdd64(&a->val, addend);
  #elif defined(GIT_BUILTIN_ATOMIC)
  	return __atomic_add_fetch(&a->val, addend, __ATOMIC_SEQ_CST);
  #elif defined(GIT_BUILTIN_SYNC)
  	return __sync_add_and_fetch(&a->val, addend);
  #else
  #	error "Unsupported architecture for atomic operations"
  #endif
  }
  
  /*
   * Atomically sets the contents of *a to be val.
   */
  GIT_INLINE(void) git_atomic64_set(git_atomic64 *a, int64_t val)
  {
  #if defined(GIT_WIN32)
  	InterlockedExchange64(&a->val, val);
  #elif defined(GIT_BUILTIN_ATOMIC)
  	__atomic_store_n(&a->val, val, __ATOMIC_SEQ_CST);
  #elif defined(GIT_BUILTIN_SYNC)
  	__sync_lock_test_and_set(&a->val, val);
  #else
  #	error "Unsupported architecture for atomic operations"
  #endif
  }
  
  /*
   * Atomically gets the contents of *a.
   * @return the contents of *a.
   */
  GIT_INLINE(int64_t) git_atomic64_get(git_atomic64 *a)
  {
  #if defined(GIT_WIN32)
  	return (int64_t)InterlockedCompareExchange64(&a->val, 0, 0);
  #elif defined(GIT_BUILTIN_ATOMIC)
  	return __atomic_load_n(&a->val, __ATOMIC_SEQ_CST);
  #elif defined(GIT_BUILTIN_SYNC)
  	return __sync_val_compare_and_swap(&a->val, 0, 0);
  #else
  #	error "Unsupported architecture for atomic operations"
  #endif
  }
  
  #endif
  
  #else
  
  #define git_threads_global_init git__noop
  
  #define git_thread unsigned int
  #define git_thread_create(thread, start_routine, arg) git__noop()
  #define git_thread_join(id, status) git__noop()
  
  /* Pthreads Mutex */
  #define git_mutex unsigned int
  #define git_mutex_init(a)	git__noop()
  #define git_mutex_init(a)	git__noop()
  #define git_mutex_lock(a)	git__noop()
  #define git_mutex_unlock(a)	git__noop()
  #define git_mutex_free(a)	git__noop()
  
  /* Pthreads condition vars */
  #define git_cond unsigned int
  #define git_cond_init(c)	git__noop()
  #define git_cond_free(c)	git__noop()
  #define git_cond_wait(c, l)	git__noop()
  #define git_cond_signal(c)	git__noop()
  #define git_cond_broadcast(c)	git__noop()
  
  /* Pthreads rwlock */
  #define git_rwlock unsigned int
  #define git_rwlock_init(a)	git__noop()
  #define git_rwlock_rdlock(a)	git__noop()
  #define git_rwlock_rdunlock(a)	git__noop()
  #define git_rwlock_wrlock(a)	git__noop()
  #define git_rwlock_wrunlock(a)	git__noop()
  #define git_rwlock_free(a)	git__noop()
  #define GIT_RWLOCK_STATIC_INIT	0
  
  
  GIT_INLINE(void) git_atomic32_set(git_atomic32 *a, int val)
  {
  	a->val = val;
  }
  
  GIT_INLINE(int) git_atomic32_inc(git_atomic32 *a)
  {
  	return ++a->val;
  }
  
  GIT_INLINE(int) git_atomic32_add(git_atomic32 *a, int32_t addend)
  {
  	a->val += addend;
  	return a->val;
  }
  
  GIT_INLINE(int) git_atomic32_dec(git_atomic32 *a)
  {
  	return --a->val;
  }
  
  GIT_INLINE(int) git_atomic32_get(git_atomic32 *a)
  {
  	return (int)a->val;
  }
  
  GIT_INLINE(void *) git_atomic__compare_and_swap(
  	void * volatile *ptr, void *oldval, void *newval)
  {
  	void *foundval = *ptr;
  	if (foundval == oldval)
  		*ptr = newval;
  	return foundval;
  }
  
  GIT_INLINE(volatile void *) git_atomic__swap(
  	void * volatile *ptr, void *newval)
  {
  	volatile void *old = *ptr;
  	*ptr = newval;
  	return old;
  }
  
  GIT_INLINE(volatile void *) git_atomic__load(void * volatile *ptr)
  {
  	return *ptr;
  }
  
  #ifdef GIT_ARCH_64
  
  GIT_INLINE(int64_t) git_atomic64_add(git_atomic64 *a, int64_t addend)
  {
  	a->val += addend;
  	return a->val;
  }
  
  GIT_INLINE(void) git_atomic64_set(git_atomic64 *a, int64_t val)
  {
  	a->val = val;
  }
  
  GIT_INLINE(int64_t) git_atomic64_get(git_atomic64 *a)
  {
  	return (int64_t)a->val;
  }
  
  #endif
  
  #endif
  
  /*
   * Atomically replace the contents of *ptr (if they are equal to oldval) with
   * newval. ptr must point to a pointer or a value that is the same size as a
   * pointer. This is semantically compatible with:
   *
   *   #define git_atomic_compare_and_swap(ptr, oldval, newval) \
   *   ({                                                       \
   *       void *foundval = *ptr;                               \
   *       if (foundval == oldval)                              \
   *           *ptr = newval;                                   \
   *       foundval;                                            \
   *   })
   *
   * @return the original contents of *ptr.
   */
  #define git_atomic_compare_and_swap(ptr, oldval, newval) \
  	git_atomic__compare_and_swap((void * volatile *)ptr, oldval, newval)
  
  /*
   * Atomically replace the contents of v with newval. v must be the same size as
   * a pointer. This is semantically compatible with:
   *
   *   #define git_atomic_swap(v, newval) \
   *   ({                                 \
   *       volatile void *old = v;        \
   *       v = newval;                    \
   *       old;                           \
   *   })
   *
   * @return the original contents of v.
   */
  #define git_atomic_swap(v, newval) \
  	(void *)git_atomic__swap((void * volatile *)&(v), newval)
  
  /*
   * Atomically reads the contents of v. v must be the same size as a pointer.
   * This is semantically compatible with:
   *
   *   #define git_atomic_load(v) v
   *
   * @return the contents of v.
   */
  #define git_atomic_load(v) \
  	(void *)git_atomic__load((void * volatile *)&(v))
  
  #if defined(GIT_THREADS)
  
  # if defined(GIT_WIN32)
  #  define GIT_MEMORY_BARRIER MemoryBarrier()
  # elif defined(GIT_BUILTIN_ATOMIC)
  #  define GIT_MEMORY_BARRIER __atomic_thread_fence(__ATOMIC_SEQ_CST)
  # elif defined(GIT_BUILTIN_SYNC)
  #  define GIT_MEMORY_BARRIER __sync_synchronize()
  # endif
  
  #else
  
  # define GIT_MEMORY_BARRIER /* noop */
  
  #endif
  
  /* Thread-local data */
  
  #if !defined(GIT_THREADS)
  # define git_tlsdata_key int
  #elif defined(GIT_WIN32)
  # define git_tlsdata_key DWORD
  #elif defined(_POSIX_THREADS)
  # define git_tlsdata_key pthread_key_t
  #else
  # error unknown threading model
  #endif
  
  /**
   * Create a thread-local data key.  The destroy function will be
   * called upon thread exit.  On some platforms, it may be called
   * when all threads have deleted their keys.
   *
   * Note that the tlsdata functions do not set an error message on
   * failure; this is because the error handling in libgit2 is itself
   * handled by thread-local data storage.
   *
   * @param key the tlsdata key
   * @param destroy_fn function pointer called upon thread exit
   * @return 0 on success, non-zero on failure
   */
  int git_tlsdata_init(git_tlsdata_key *key, void (GIT_SYSTEM_CALL *destroy_fn)(void *));
  
  /**
   * Set a the thread-local value for the given key.
   *
   * @param key the tlsdata key to store data on
   * @param value the pointer to store
   * @return 0 on success, non-zero on failure
   */
  int git_tlsdata_set(git_tlsdata_key key, void *value);
  
  /**
   * Get the thread-local value for the given key.
   *
   * @param key the tlsdata key to retrieve the value of
   * @return the pointer stored with git_tlsdata_set
   */
  void *git_tlsdata_get(git_tlsdata_key key);
  
  /**
   * Delete the given thread-local key.
   *
   * @param key the tlsdata key to dispose
   * @return 0 on success, non-zero on failure
   */
  int git_tlsdata_dispose(git_tlsdata_key key);
  
  #endif
  

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