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LibC+LibPthread: Implement pthread_atfork()

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This required a bit of rearchitecture, as pthread_atfork() required a
mutex, and duplicating a mutex impl for it was silly.
As such, this patch moves some standalone bits of pthread into LibC and
uses those to implement atfork().
It should be noted that for programs that don't use atfork(), this
mechanism only costs two atomic loads (as opposed to the normal mutex
lock+unlock) :^)
This commit is contained in:
AnotherTest 2021-02-14 18:34:18 +03:30 • committed by Andreas Kling
parent 8e074f8665
commit bb777459a0
6 changed files with 231 additions and 37 deletions
Download patch file Download diff file Expand all files Collapse all files

41
Userland/Libraries/LibPthread/pthread.cpp
View file

@ -30,6 +30,7 @@
#include <AK/StdLibExtras.h>
#include <Kernel/API/Syscall.h>
#include <LibSystem/syscall.h>
#include <bits/pthread_integration.h>
#include <limits.h>
#include <pthread.h>
#include <serenity.h>
@ -110,7 +111,7 @@ static int create_thread(pthread_t* thread, void* (*entry)(void*), void* argumen
int pthread_self()
{
return gettid();
return __pthread_self();
}
int pthread_create(pthread_t* thread, pthread_attr_t* attributes, void* (*start_routine)(void*), void* argument_to_start_routine)
@ -172,11 +173,7 @@ int pthread_sigmask(int how, const sigset_t* set, sigset_t* old_set)
int pthread_mutex_init(pthread_mutex_t* mutex, const pthread_mutexattr_t* attributes)
{
mutex->lock = 0;
mutex->owner = 0;
mutex->level = 0;
mutex->type = attributes ? attributes->type : PTHREAD_MUTEX_NORMAL;
return 0;
return __pthread_mutex_init(mutex, attributes);
}
int pthread_mutex_destroy(pthread_mutex_t*)
@ -186,22 +183,7 @@ int pthread_mutex_destroy(pthread_mutex_t*)
int pthread_mutex_lock(pthread_mutex_t* mutex)
{
auto& atomic = reinterpret_cast<Atomic<u32>&>(mutex->lock);
pthread_t this_thread = pthread_self();
for (;;) {
u32 expected = false;
if (!atomic.compare_exchange_strong(expected, true, AK::memory_order_acq_rel)) {
if (mutex->type == PTHREAD_MUTEX_RECURSIVE && mutex->owner == this_thread) {
mutex->level++;
return 0;
}
sched_yield();
continue;
}
mutex->owner = this_thread;
mutex->level = 0;
return 0;
}
return __pthread_mutex_lock(mutex);
}
int pthread_mutex_trylock(pthread_mutex_t* mutex)
@ -222,13 +204,7 @@ int pthread_mutex_trylock(pthread_mutex_t* mutex)
int pthread_mutex_unlock(pthread_mutex_t* mutex)
{
if (mutex->type == PTHREAD_MUTEX_RECURSIVE && mutex->level > 0) {
mutex->level--;
return 0;
}
mutex->owner = 0;
mutex->lock = 0;
return 0;
return __pthread_mutex_unlock(mutex);
}
int pthread_mutexattr_init(pthread_mutexattr_t* attr)
@ -922,9 +898,12 @@ int pthread_rwlockattr_setpshared(pthread_rwlockattr_t*, int)
ASSERT_NOT_REACHED();
}
int pthread_atfork(void (*)(void), void (*)(void), void (*)(void))
int pthread_atfork(void (*prepare)(void), void (*parent)(void), void (*child)(void))
{
ASSERT_NOT_REACHED();
__pthread_fork_atfork_register_prepare(prepare);
__pthread_fork_atfork_register_parent(parent);
__pthread_fork_atfork_register_child(child);
return 0;
}
} // extern "C"

11
Userland/Libraries/LibPthread/pthread.h
View file

@ -26,6 +26,7 @@
#pragma once
#include <bits/pthread_integration.h>
#include <sched.h>
#include <stdint.h>
#include <sys/cdefs.h>
@ -75,13 +76,11 @@ int pthread_setspecific(pthread_key_t key, const void* value);
int pthread_getschedparam(pthread_t thread, int* policy, struct sched_param* param);
int pthread_setschedparam(pthread_t thread, int policy, const struct sched_param* param);
#define PTHREAD_MUTEX_NORMAL 0
#define PTHREAD_MUTEX_RECURSIVE 1
#define PTHREAD_MUTEX_NORMAL __PTHREAD_MUTEX_NORMAL
#define PTHREAD_MUTEX_RECURSIVE __PTHREAD_MUTEX_RECURSIVE
#define PTHREAD_MUTEX_DEFAULT PTHREAD_MUTEX_NORMAL
#define PTHREAD_MUTEX_INITIALIZER \
{ \
0, 0, 0, PTHREAD_MUTEX_DEFAULT \
}
#define PTHREAD_MUTEX_INITIALIZER __PTHREAD_MUTEX_INITIALIZER
#define PTHREAD_COND_INITIALIZER \
{ \
0, 0, CLOCK_MONOTONIC_COARSE \