From 39539495acb24abfb4dee551e3e9f2e696be7abf Mon Sep 17 00:00:00 2001 From: =?utf8?q?Nguy=E1=BB=85n=20Th=C3=A1i=20Ng=E1=BB=8Dc=20Duy?= Date: Tue, 25 Mar 2014 20:41:41 +0700 Subject: [PATCH] index-pack: work around thread-unsafe pread() MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit Multi-threaing of index-pack was disabled with c0f8654 (index-pack: Disable threading on cygwin - 2012-06-26), because pread() implementations for Cygwin and MSYS were not thread safe. Recent Cygwin does offer usable pread() and we enabled multi-threading with 103d530f (Cygwin 1.7 has thread-safe pread, 2013-07-19). Work around this problem on platforms with a thread-unsafe pread() emulation by opening one file handle per thread; it would prevent parallel pread() on different file handles from stepping on each other. Also remove NO_THREAD_SAFE_PREAD that was introduced in c0f8654 because it's no longer used anywhere. This workaround is unconditional, even for platforms with thread-safe pread() because the overhead is small (a couple file handles more) and not worth fragmenting the code. Signed-off-by: Nguyễn Thái Ngọc Duy Tested-by: Johannes Sixt Signed-off-by: Junio C Hamano --- Makefile | 7 ------- builtin/index-pack.c | 27 +++++++++++++++++---------- config.mak.uname | 1 - 3 files changed, 17 insertions(+), 18 deletions(-) diff --git a/Makefile b/Makefile index dddaf4f287..00a70840eb 100644 --- a/Makefile +++ b/Makefile @@ -191,9 +191,6 @@ all:: # Define NO_STRUCT_ITIMERVAL if you don't have struct itimerval # This also implies NO_SETITIMER # -# Define NO_THREAD_SAFE_PREAD if your pread() implementation is not -# thread-safe. (e.g. compat/pread.c or cygwin) -# # Define NO_FAST_WORKING_DIRECTORY if accessing objects in pack files is # generally faster on your platform than accessing the working directory. # @@ -1341,10 +1338,6 @@ endif ifdef NO_PREAD COMPAT_CFLAGS += -DNO_PREAD COMPAT_OBJS += compat/pread.o - NO_THREAD_SAFE_PREAD = YesPlease -endif -ifdef NO_THREAD_SAFE_PREAD - BASIC_CFLAGS += -DNO_THREAD_SAFE_PREAD endif ifdef NO_FAST_WORKING_DIRECTORY BASIC_CFLAGS += -DNO_FAST_WORKING_DIRECTORY diff --git a/builtin/index-pack.c b/builtin/index-pack.c index 2f37a38fbc..ed489bbe9a 100644 --- a/builtin/index-pack.c +++ b/builtin/index-pack.c @@ -40,17 +40,13 @@ struct base_data { int ofs_first, ofs_last; }; -#if !defined(NO_PTHREADS) && defined(NO_THREAD_SAFE_PREAD) -/* pread() emulation is not thread-safe. Disable threading. */ -#define NO_PTHREADS -#endif - struct thread_local { #ifndef NO_PTHREADS pthread_t thread; #endif struct base_data *base_cache; size_t base_cache_used; + int pack_fd; }; /* @@ -91,7 +87,8 @@ static off_t consumed_bytes; static unsigned deepest_delta; static git_SHA_CTX input_ctx; static uint32_t input_crc32; -static int input_fd, output_fd, pack_fd; +static int input_fd, output_fd; +static const char *curr_pack; #ifndef NO_PTHREADS @@ -134,6 +131,7 @@ static inline void unlock_mutex(pthread_mutex_t *mutex) */ static void init_thread(void) { + int i; init_recursive_mutex(&read_mutex); pthread_mutex_init(&counter_mutex, NULL); pthread_mutex_init(&work_mutex, NULL); @@ -141,11 +139,18 @@ static void init_thread(void) pthread_mutex_init(&deepest_delta_mutex, NULL); pthread_key_create(&key, NULL); thread_data = xcalloc(nr_threads, sizeof(*thread_data)); + for (i = 0; i < nr_threads; i++) { + thread_data[i].pack_fd = open(curr_pack, O_RDONLY); + if (thread_data[i].pack_fd == -1) + die_errno(_("unable to open %s"), curr_pack); + } + threads_active = 1; } static void cleanup_thread(void) { + int i; if (!threads_active) return; threads_active = 0; @@ -154,6 +159,8 @@ static void cleanup_thread(void) pthread_mutex_destroy(&work_mutex); if (show_stat) pthread_mutex_destroy(&deepest_delta_mutex); + for (i = 0; i < nr_threads; i++) + close(thread_data[i].pack_fd); pthread_key_delete(key); free(thread_data); } @@ -288,13 +295,13 @@ static const char *open_pack_file(const char *pack_name) output_fd = open(pack_name, O_CREAT|O_EXCL|O_RDWR, 0600); if (output_fd < 0) die_errno(_("unable to create '%s'"), pack_name); - pack_fd = output_fd; + nothread_data.pack_fd = output_fd; } else { input_fd = open(pack_name, O_RDONLY); if (input_fd < 0) die_errno(_("cannot open packfile '%s'"), pack_name); output_fd = -1; - pack_fd = input_fd; + nothread_data.pack_fd = input_fd; } git_SHA1_Init(&input_ctx); return pack_name; @@ -542,7 +549,7 @@ static void *unpack_data(struct object_entry *obj, do { ssize_t n = (len < 64*1024) ? len : 64*1024; - n = pread(pack_fd, inbuf, n, from); + n = pread(get_thread_data()->pack_fd, inbuf, n, from); if (n < 0) die_errno(_("cannot pread pack file")); if (!n) @@ -1490,7 +1497,7 @@ static void show_pack_info(int stat_only) int cmd_index_pack(int argc, const char **argv, const char *prefix) { int i, fix_thin_pack = 0, verify = 0, stat_only = 0; - const char *curr_pack, *curr_index; + const char *curr_index; const char *index_name = NULL, *pack_name = NULL; const char *keep_name = NULL, *keep_msg = NULL; char *index_name_buf = NULL, *keep_name_buf = NULL; diff --git a/config.mak.uname b/config.mak.uname index 7d31fad241..db5c249b4c 100644 --- a/config.mak.uname +++ b/config.mak.uname @@ -158,7 +158,6 @@ ifeq ($(uname_O),Cygwin) NO_SYMLINK_HEAD = YesPlease NO_IPV6 = YesPlease OLD_ICONV = UnfortunatelyYes - NO_THREAD_SAFE_PREAD = YesPlease # There are conflicting reports about this. # On some boxes NO_MMAP is needed, and not so elsewhere. # Try commenting this out if you suspect MMAP is more efficient -- 2.11.4.GIT