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TLS: Thread Local Storage #82

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Merged
merged 1 commit into from
Jun 21, 2016
Merged

TLS: Thread Local Storage #82

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21 changes: 21 additions & 0 deletions configure.ac
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Original file line number Diff line number Diff line change
Expand Up @@ -108,6 +108,27 @@ AC_ARG_WITH([swift-toolchain],
AM_CONDITIONAL(HAVE_SWIFT, $have_swift)
AC_SUBST([SWIFTC])

#
# Enable __thread based TSD on platforms where it is efficient
# Allow override based on command line argument to configure
#
AC_CANONICAL_TARGET
AC_ARG_ENABLE([thread-local-storage],
[AS_HELP_STRING([--enable-thread-local-storage],
[Enable usage of thread local storage via __thread])],,
[case $target_os in
linux*)
enable_thread_local_storage=yes
;;
*)
enable_thread_local_storage=no
esac]
)
AS_IF([test "x$enable_thread_local_storage" = "xyes"],
[AC_DEFINE(DISPATCH_USE_THREAD_LOCAL_STORAGE, 1,
[Enable usage of thread local storage via __thread])]
)

AC_USE_SYSTEM_EXTENSIONS
AM_INIT_AUTOMAKE([foreign no-dependencies subdir-objects])
LT_INIT([disable-static])
Expand Down
11 changes: 5 additions & 6 deletions src/init.c
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Expand Up @@ -67,7 +67,10 @@ void *(*_dispatch_begin_NSAutoReleasePool)(void);
void (*_dispatch_end_NSAutoReleasePool)(void *);
#endif

#if !DISPATCH_USE_DIRECT_TSD
#if DISPATCH_USE_THREAD_LOCAL_STORAGE
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make that

-#if !DISPATCH_USE_DIRECT_TSD
+#if DISPATCH_USE_THREAD_LOCAL_STORAGE
+__thread struct dispatch_tsd __dispatch_tsd;
+pthread_key_t __dispatch_tsd_key;
+-#elif !DISPATCH_USE_DIRECT_TSD

instead of linux_sbuts.c

__thread struct dispatch_tsd __dispatch_tsd;
pthread_key_t __dispatch_tsd_key;
#elif !DISPATCH_USE_DIRECT_TSD
pthread_key_t dispatch_queue_key;
pthread_key_t dispatch_frame_key;
pthread_key_t dispatch_cache_key;
Expand All @@ -82,7 +85,7 @@ pthread_key_t dispatch_bcounter_key;
pthread_key_t dispatch_sema4_key;
pthread_key_t dispatch_voucher_key;
pthread_key_t dispatch_deferred_items_key;
#endif // !DISPATCH_USE_DIRECT_TSD
#endif // !DISPATCH_USE_DIRECT_TSD && !DISPATCH_USE_THREAD_LOCAL_STORAGE

#if VOUCHER_USE_MACH_VOUCHER
dispatch_once_t _voucher_task_mach_voucher_pred;
Expand Down Expand Up @@ -184,10 +187,6 @@ const struct dispatch_tsd_indexes_s dispatch_tsd_indexes = {
.dti_voucher_index = dispatch_voucher_key,
.dti_qos_class_index = dispatch_priority_key,
};
#else // DISPATCH_USE_DIRECT_TSD
#ifndef __LINUX_PORT_HDD__
#error Not implemented on this platform
#endif
#endif // DISPATCH_USE_DIRECT_TSD

// 6618342 Contact the team that owns the Instrument DTrace probe before
Expand Down
57 changes: 57 additions & 0 deletions src/queue.c
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Expand Up @@ -894,6 +894,9 @@ libdispatch_init(void)
#endif
#endif

#if DISPATCH_USE_THREAD_LOCAL_STORAGE
_dispatch_thread_key_create(&__dispatch_tsd_key, _libdispatch_tsd_cleanup);
#else
_dispatch_thread_key_create(&dispatch_queue_key, _dispatch_queue_cleanup);
_dispatch_thread_key_create(&dispatch_deferred_items_key,
_dispatch_deferred_items_cleanup);
Expand All @@ -913,6 +916,7 @@ libdispatch_init(void)
_dispatch_thread_semaphore_dispose);
}
#endif
#endif

#if DISPATCH_USE_RESOLVERS // rdar://problem/8541707
_dispatch_main_q.do_targetq = &_dispatch_root_queues[
Expand Down Expand Up @@ -967,6 +971,59 @@ _dispatch_get_mach_host_port(void)
}
#endif

#if DISPATCH_USE_THREAD_LOCAL_STORAGE
#include <unistd.h>
#include <sys/syscall.h>

#ifdef SYS_gettid
DISPATCH_ALWAYS_INLINE
static inline pid_t
gettid(void)
{
return (pid_t) syscall(SYS_gettid);
}
#else
#error "SYS_gettid unavailable on this system"
#endif

#define _tsd_call_cleanup(k, f) do { \
if ((f) && tsd->k) ((void(*)(void*))(f))(tsd->k); \
} while (0)

void
_libdispatch_tsd_cleanup(void *ctx)
{
struct dispatch_tsd *tsd = (struct dispatch_tsd*) ctx;

_tsd_call_cleanup(dispatch_queue_key, _dispatch_queue_cleanup);
_tsd_call_cleanup(dispatch_frame_key, _dispatch_frame_cleanup);
_tsd_call_cleanup(dispatch_cache_key, _dispatch_cache_cleanup);
_tsd_call_cleanup(dispatch_context_key, _dispatch_context_cleanup);
_tsd_call_cleanup(dispatch_pthread_root_queue_observer_hooks_key,
NULL);
_tsd_call_cleanup(dispatch_defaultpriority_key, NULL);
#if DISPATCH_PERF_MON && !DISPATCH_INTROSPECTION
_tsd_call_cleanup(dispatch_bcounter_key, NULL);
#endif
#if DISPATCH_LOCK_USE_SEMAPHORE_FALLBACK
_tsd_call_cleanup(dispatch_sema4_key, _dispatch_thread_semaphore_dispose);
#endif
_tsd_call_cleanup(dispatch_priority_key, NULL);
_tsd_call_cleanup(dispatch_voucher_key, _voucher_thread_cleanup);
_tsd_call_cleanup(dispatch_deferred_items_key,
_dispatch_deferred_items_cleanup);
tsd->tid = 0;
}

DISPATCH_NOINLINE
void
libdispatch_tsd_init(void)
{
pthread_setspecific(__dispatch_tsd_key, &__dispatch_tsd);
__dispatch_tsd.tid = gettid();
}
#endif

DISPATCH_EXPORT DISPATCH_NOTHROW
void
dispatch_atfork_child(void)
Expand Down
1 change: 1 addition & 0 deletions src/shims/linux_stubs.c
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Expand Up @@ -57,3 +57,4 @@ unsigned short dispatch_callout__return_semaphore;
unsigned short dispatch_queue__push_semaphore;
void (*_dispatch_block_special_invoke)(void*);
struct dispatch_queue_attr_s _dispatch_queue_attr_concurrent;

3 changes: 2 additions & 1 deletion src/shims/lock.h
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Expand Up @@ -98,7 +98,8 @@ typedef pid_t dispatch_lock_owner;
#define DLOCK_OWNER_MASK ((dispatch_lock)FUTEX_TID_MASK)
#define DLOCK_WAITERS_BIT ((dispatch_lock)FUTEX_WAITERS)
#define DLOCK_FAILED_TRYLOCK_BIT ((dispatch_lock)FUTEX_OWNER_DIED)
#define _dispatch_tid_self() syscall(SYS_gettid) /* FIXME: should be cached in TSD instead of doing syscall each time */
#define _dispatch_tid_self() \
((dispatch_lock_owner)(_dispatch_get_tsd_base()->tid))

DISPATCH_ALWAYS_INLINE
static inline bool
Expand Down
75 changes: 73 additions & 2 deletions src/shims/tsd.h
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Expand Up @@ -92,10 +92,76 @@ _dispatch_thread_key_create(const unsigned long *k, void (*d)(void *))
if (!*k || !d) return;
dispatch_assert_zero(pthread_key_init_np((int)*k, d));
}
#elif DISPATCH_USE_THREAD_LOCAL_STORAGE

DISPATCH_TSD_INLINE
static inline void
_dispatch_thread_key_create(pthread_key_t *k, void (*d)(void *))
{
dispatch_assert_zero(pthread_key_create(k, d));
}

struct dispatch_tsd {
pid_t tid;
void *dispatch_queue_key;
void *dispatch_frame_key;
void *dispatch_cache_key;
void *dispatch_context_key;
void *dispatch_pthread_root_queue_observer_hooks_key;
void *dispatch_defaultpriority_key;
#if DISPATCH_INTROSPECTION
void *dispatch_introspection_key;
#elif DISPATCH_PERF_MON
void *dispatch_bcounter_key;
#endif
#if DISPATCH_LOCK_USE_SEMAPHORE_FALLBACK
void *dispatch_sema4_key;
#endif
void *dispatch_priority_key;
void *dispatch_voucher_key;
void *dispatch_deferred_items_key;
};

extern __thread struct dispatch_tsd __dispatch_tsd;
extern pthread_key_t __dispatch_tsd_key;
extern void libdispatch_tsd_init(void);
extern void _libdispatch_tsd_cleanup(void *ctx);

DISPATCH_ALWAYS_INLINE
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you should also add DISPATCH_PURE here, which can help have the compiler hoist the lazy init to the top.

static inline struct dispatch_tsd *
_dispatch_get_tsd_base(void)
{
if (unlikely(__dispatch_tsd.tid == 0)) {
libdispatch_tsd_init();
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Adding a OS_COMPILER_CAN_ASSUME(__dispatch_tsd.tid != 0) may help clang to also not call that lazy init several times for the cases when several TSD accesses are performed

}
OS_COMPILER_CAN_ASSUME(__dispatch_tsd.tid != 0);
return &__dispatch_tsd;
}

#define _dispatch_thread_getspecific(key) \
(_dispatch_get_tsd_base()->key)
#define _dispatch_thread_setspecific(key, value) \
(void)(_dispatch_get_tsd_base()->key = (value))

#define _dispatch_thread_getspecific_pair(k1, p1, k2, p2) \
( *(p1) = _dispatch_thread_getspecific(k1), \
*(p2) = _dispatch_thread_getspecific(k2) )

#define _dispatch_thread_getspecific_packed_pair(k1, k2, p) \
( (p)[0] = _dispatch_thread_getspecific(k1), \
(p)[1] = _dispatch_thread_getspecific(k2) )

#define _dispatch_thread_setspecific_pair(k1, p1, k2, p2) \
( _dispatch_thread_setspecific(k1,p1), \
_dispatch_thread_setspecific(k2,p2) )

#define _dispatch_thread_setspecific_packed_pair(k1, k2, p) \
( _dispatch_thread_setspecific(k1,(p)[0]), \
_dispatch_thread_setspecific(k2,(p)[1]) )

#else
extern pthread_key_t dispatch_queue_key;
extern pthread_key_t dispatch_frame_key;
extern pthread_key_t dispatch_sema4_key;
extern pthread_key_t dispatch_cache_key;
extern pthread_key_t dispatch_context_key;
extern pthread_key_t dispatch_pthread_root_queue_observer_hooks_key;
Expand All @@ -105,7 +171,8 @@ extern pthread_key_t dispatch_introspection_key;
#elif DISPATCH_PERF_MON
extern pthread_key_t dispatch_bcounter_key;
#endif
extern pthread_key_t dispatch_cache_key;
extern pthread_key_t dispatch_sema4_key;
extern pthread_key_t dispatch_priority_key;
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eeew thanks

extern pthread_key_t dispatch_voucher_key;
extern pthread_key_t dispatch_deferred_items_key;

Expand All @@ -117,6 +184,7 @@ _dispatch_thread_key_create(pthread_key_t *k, void (*d)(void *))
}
#endif

#ifndef DISPATCH_USE_THREAD_LOCAL_STORAGE
DISPATCH_TSD_INLINE
static inline void
_dispatch_thread_setspecific(pthread_key_t k, void *v)
Expand Down Expand Up @@ -210,6 +278,7 @@ _dispatch_thread_setspecific_packed_pair(pthread_key_t k1, pthread_key_t k2,
_dispatch_thread_setspecific(k1, p[0]);
_dispatch_thread_setspecific(k2, p[1]);
}
#endif

#if TARGET_OS_WIN32
#define _dispatch_thread_self() ((uintptr_t)GetCurrentThreadId())
Expand All @@ -228,6 +297,8 @@ _dispatch_thread_setspecific_packed_pair(pthread_key_t k1, pthread_key_t k2,
#if DISPATCH_USE_DIRECT_TSD
#define _dispatch_thread_port() ((mach_port_t)(uintptr_t)\
_dispatch_thread_getspecific(_PTHREAD_TSD_SLOT_MACH_THREAD_SELF))
#elif DISPATCH_USE_THREAD_LOCAL_STORAGE
#define _dispatch_thread_port() ((mach_port_t)(_dispatch_get_tsd_base()->tid))
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I really don't like this name, _dispatch_thread_port() is a mach concept, so we should ban the use of this on the linux port, and instead have _dispatch_tid_self() in lock.h expand to (_dispatch_get_tsd_base()->tid).

and if there are calls to _dispatch_thread_port() in non mach code, we should most likely port them to _dispatch_tid_self() or guard the code with a #if HAVE_MACH

IOW that thing here should be in a #if HAVE_MACH this way:

#if TARGET_OS_WIN32
#define _dispatch_thread_port() ((mach_port_t)0)
#elif HAVE_MACH
#if DISPATCH_USE_DIRECT_TSD
#define _dispatch_thread_port() ((mach_port_t)(uintptr_t)\
        _dispatch_thread_getspecific(_PTHREAD_TSD_SLOT_MACH_THREAD_SELF))
#else
#define _dispatch_thread_port() pthread_mach_thread_np(_dispatch_thread_self())
#endif
#endif // HAVE_MACH

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Technically definining it for Windows is not the right way, but let's leave that part alone. it should also define _dispatch_tid_self() eventually if someone decides to re-port dispatch in the future, the same way I'm asking you to do for linux.

#else
#define _dispatch_thread_port() pthread_mach_thread_np(_dispatch_thread_self())
#endif
Expand Down