Revert barrier-based LSan threading race workaround

The extra "barrier" approach was too much code whose sole purpose
was to work around a race that is not even ours (i.e. in LSan's
teardown code).

In preparation for queuing a solution taking a much-less-invasive
approach, let's revert them.

Author: gitster

Makefile

@@ -141,10 +141,6 @@ include shared.mak
 #
 # Define NO_PTHREADS if you do not have or do not want to use Pthreads.
 #
-# Define THREAD_BARRIER_PTHREAD if your system has pthread_barrier_t. Barrier
-# support is optional and is only helpful when building with SANITIZE=leak, as
-# it is used to eliminate some races in the leak-checker.
-#
 # Define NO_PREAD if you have a problem with pread() system call (e.g.
 # cygwin1.dll before v1.5.22).
 #
@@ -2083,9 +2079,6 @@ ifdef NO_PTHREADS
 else
 	BASIC_CFLAGS += $(PTHREAD_CFLAGS)
 	EXTLIBS += $(PTHREAD_LIBS)
-	ifdef THREAD_BARRIER_PTHREAD
-		BASIC_CFLAGS += -DTHREAD_BARRIER_PTHREAD
-	endif
 endif
 
 ifdef HAVE_PATHS_H

builtin/grep.c

@@ -101,9 +101,6 @@ static pthread_cond_t cond_write;
 /* Signalled when we are finished with everything. */
 static pthread_cond_t cond_result;
 
-/* Synchronize the start of all threads */
-static maybe_thread_barrier_t start_barrier;
-
 static int skip_first_line;
 
 static void add_work(struct grep_opt *opt, struct grep_source *gs)
@@ -201,8 +198,6 @@ static void *run(void *arg)
 	int hit = 0;
 	struct grep_opt *opt = arg;
 
-	maybe_thread_barrier_wait(&start_barrier);
-
 	while (1) {
 		struct work_item *w = get_work();
 		if (!w)
@@ -234,7 +229,6 @@ static void start_threads(struct grep_opt *opt)
 	pthread_cond_init(&cond_add, NULL);
 	pthread_cond_init(&cond_write, NULL);
 	pthread_cond_init(&cond_result, NULL);
-	maybe_thread_barrier_init(&start_barrier, NULL, num_threads + 1);
 	grep_use_locks = 1;
 	enable_obj_read_lock();
 
@@ -254,7 +248,6 @@ static void start_threads(struct grep_opt *opt)
 			die(_("grep: failed to create thread: %s"),
 			    strerror(err));
 	}
-	maybe_thread_barrier_wait(&start_barrier);
 }
 
 static int wait_all(void)
@@ -291,7 +284,6 @@ static int wait_all(void)
 	pthread_cond_destroy(&cond_add);
 	pthread_cond_destroy(&cond_write);
 	pthread_cond_destroy(&cond_result);
-	maybe_thread_barrier_destroy(&start_barrier);
 	grep_use_locks = 0;
 	disable_obj_read_lock();
 

builtin/index-pack.c

@@ -185,8 +185,6 @@ static pthread_mutex_t deepest_delta_mutex;
 
 static pthread_key_t key;
 
-static maybe_thread_barrier_t start_barrier;
-
 static inline void lock_mutex(pthread_mutex_t *mutex)
 {
 	if (threads_active)
@@ -211,7 +209,6 @@ static void init_thread(void)
 	if (show_stat)
 		pthread_mutex_init(&deepest_delta_mutex, NULL);
 	pthread_key_create(&key, NULL);
-	maybe_thread_barrier_init(&start_barrier, NULL, nr_threads);
 	CALLOC_ARRAY(thread_data, nr_threads);
 	for (i = 0; i < nr_threads; i++) {
 		thread_data[i].pack_fd = xopen(curr_pack, O_RDONLY);
@@ -234,7 +231,6 @@ static void cleanup_thread(void)
 	for (i = 0; i < nr_threads; i++)
 		close(thread_data[i].pack_fd);
 	pthread_key_delete(key);
-	maybe_thread_barrier_destroy(&start_barrier);
 	free(thread_data);
 }
 
@@ -1104,8 +1100,6 @@ static int compare_ref_delta_entry(const void *a, const void *b)
 
 static void *threaded_second_pass(void *data)
 {
-	if (threads_active)
-		maybe_thread_barrier_wait(&start_barrier);
 	if (data)
 		set_thread_data(data);
 	for (;;) {

ci/lib.sh

@@ -385,7 +385,6 @@ linux-musl)
 	;;
 linux-leaks|linux-reftable-leaks)
 	export SANITIZE=leak
-	export THREAD_BARRIER_PTHREAD=1
 	;;
 linux-asan-ubsan)
 	export SANITIZE=address,undefined

thread-utils.h

@@ -53,22 +53,5 @@ int dummy_pthread_init(void *);
 int online_cpus(void);
 int init_recursive_mutex(pthread_mutex_t*);
 
-#ifdef THREAD_BARRIER_PTHREAD
-#define maybe_thread_barrier_t pthread_barrier_t
-#define maybe_thread_barrier_init pthread_barrier_init
-#define maybe_thread_barrier_wait pthread_barrier_wait
-#define maybe_thread_barrier_destroy pthread_barrier_destroy
-#else
-#define maybe_thread_barrier_t int
-static inline int maybe_thread_barrier_init(maybe_thread_barrier_t *b UNUSED,
-					    void *attr UNUSED,
-					    unsigned nr UNUSED)
-{
-	errno = ENOSYS;
-	return -1;
-}
-#define maybe_thread_barrier_wait(barrier)
-#define maybe_thread_barrier_destroy(barrier)
-#endif
 
 #endif /* THREAD_COMPAT_H */