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runtime/cgo: reduce runtime init done check using atomic

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Every call from C to Go does acquire a mutex to check whether Go runtime
has been fully initialized. This often does not matter, because the lock
is held only briefly. However, with code that does a lot of parallel
calls from C to Go could cause heavy contention on the mutex.

Since this is an initialization guard, we can double check with atomic
operation to provide a fast path in case the initialization is done.
With this CL, program in #60961 reduces from ~2.7s to ~1.8s.

Fixes #60961

Change-Id: Iba4cabbee3c9bc646e70ef7eb074212ba63fdc04
Reviewed-on: https://go-review.googlesource.com/c/go/+/505455
Reviewed-by: Heschi Kreinick <heschi@google.com>
Auto-Submit: Cuong Manh Le <cuong.manhle.vn@gmail.com>
Run-TryBot: Ian Lance Taylor <iant@google.com>
Auto-Submit: Ian Lance Taylor <iant@google.com>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Cuong Manh Le <cuong.manhle.vn@gmail.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
This commit is contained in:
Cuong Manh Le 2023-06-23 13:20:33 +07:00 committed by Gopher Robot
parent d1612071d9
commit b104a0ef32
1 changed files with 31 additions and 31 deletions
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62
src/runtime/cgo/gcc_libinit.c
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@ -41,30 +41,37 @@ x_cgo_sys_thread_create(void* (*func)(void*), void* arg) {
uintptr_t
_cgo_wait_runtime_init_done(void) {
void (*pfn)(struct context_arg*);
pfn = __atomic_load_n(&cgo_context_function, __ATOMIC_CONSUME);
pthread_mutex_lock(&runtime_init_mu);
while (runtime_init_done == 0) {
pthread_cond_wait(&runtime_init_cond, &runtime_init_mu);
int done = 2;
if (__atomic_load_n(&runtime_init_done, __ATOMIC_CONSUME) != done) {
pthread_mutex_lock(&runtime_init_mu);
while (__atomic_load_n(&runtime_init_done, __ATOMIC_CONSUME) == 0) {
pthread_cond_wait(&runtime_init_cond, &runtime_init_mu);
}
// The key and x_cgo_pthread_key_created are for the whole program,
// whereas the specific and destructor is per thread.
if (x_cgo_pthread_key_created == 0 && pthread_key_create(&pthread_g, pthread_key_destructor) == 0) {
x_cgo_pthread_key_created = 1;
}
// TODO(iant): For the case of a new C thread calling into Go, such
// as when using -buildmode=c-archive, we know that Go runtime
// initialization is complete but we do not know that all Go init
// functions have been run. We should not fetch cgo_context_function
// until they have been, because that is where a call to
// SetCgoTraceback is likely to occur. We are going to wait for Go
// initialization to be complete anyhow, later, by waiting for
// main_init_done to be closed in cgocallbackg1. We should wait here
// instead. See also issue #15943.
pfn = __atomic_load_n(&cgo_context_function, __ATOMIC_CONSUME);
__atomic_store_n(&runtime_init_done, done, __ATOMIC_RELEASE);
pthread_mutex_unlock(&runtime_init_mu);
}
// The key and x_cgo_pthread_key_created are for the whole program,
// whereas the specific and destructor is per thread.
if (x_cgo_pthread_key_created == 0 && pthread_key_create(&pthread_g, pthread_key_destructor) == 0) {
x_cgo_pthread_key_created = 1;
}
// TODO(iant): For the case of a new C thread calling into Go, such
// as when using -buildmode=c-archive, we know that Go runtime
// initialization is complete but we do not know that all Go init
// functions have been run. We should not fetch cgo_context_function
// until they have been, because that is where a call to
// SetCgoTraceback is likely to occur. We are going to wait for Go
// initialization to be complete anyhow, later, by waiting for
// main_init_done to be closed in cgocallbackg1. We should wait here
// instead. See also issue #15943.
pfn = cgo_context_function;
pthread_mutex_unlock(&runtime_init_mu);
if (pfn != nil) {
struct context_arg arg;
@ -88,7 +95,7 @@ void x_cgo_bindm(void* g) {
void
x_cgo_notify_runtime_init_done(void* dummy __attribute__ ((unused))) {
pthread_mutex_lock(&runtime_init_mu);
runtime_init_done = 1;
__atomic_store_n(&runtime_init_done, 1, __ATOMIC_RELEASE);
pthread_cond_broadcast(&runtime_init_cond);
pthread_mutex_unlock(&runtime_init_mu);
}
@ -96,19 +103,12 @@ x_cgo_notify_runtime_init_done(void* dummy __attribute__ ((unused))) {
// Sets the context function to call to record the traceback context
// when calling a Go function from C code. Called from runtime.SetCgoTraceback.
void x_cgo_set_context_function(void (*context)(struct context_arg*)) {
pthread_mutex_lock(&runtime_init_mu);
cgo_context_function = context;
pthread_mutex_unlock(&runtime_init_mu);
__atomic_store_n(&cgo_context_function, context, __ATOMIC_RELEASE);
}
// Gets the context function.
void (*(_cgo_get_context_function(void)))(struct context_arg*) {
void (*ret)(struct context_arg*);
pthread_mutex_lock(&runtime_init_mu);
ret = cgo_context_function;
pthread_mutex_unlock(&runtime_init_mu);
return ret;
return __atomic_load_n(&cgo_context_function, __ATOMIC_CONSUME);
}
// _cgo_try_pthread_create retries pthread_create if it fails with