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Added semaphore with futex (hopefully fast)

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This commit is contained in:
Lemaitre 2021-10-05 23:46:03 +02:00
parent cf598d09e4
commit 446ad21138
13 changed files with 200 additions and 13 deletions
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10
examples/thread.c
View file

@ -12,9 +12,14 @@
#include "libc/thread/self.h"
#include "libc/thread/detach.h"
#include "libc/thread/join.h"
#include "libc/thread/nativesem.h"
#include "libc/time/time.h"
cthread_native_sem_t semaphore;
int worker(void* arg) {
cthread_native_sem_signal(&semaphore);
cthread_t self = cthread_self();
int tid = self->tid;
sleep(1);
@ -25,9 +30,12 @@ int worker(void* arg) {
}
int main() {
cthread_native_sem_init(&semaphore, 0);
cthread_t thread;
int rc = cthread_create(&thread, NULL, &worker, NULL);
if (rc == 0) {
cthread_native_sem_wait(&semaphore, 0, 0, NULL);
//printf("thread created: %p\n", thread);
sleep(1);
#if 1
@ -36,6 +44,8 @@ int main() {
rc = cthread_detach(thread);
sleep(2);
#endif
cthread_native_sem_signal(&semaphore);
cthread_native_sem_wait(&semaphore, 0, 0, NULL);
//printf("thread joined: %p -> %d\n", thread, rc);
} else {
printf("ERROR: thread could not be started: %d\n", rc);

12
libc/sysv/consts.sh
View file

@ -1928,13 +1928,13 @@ syscon misc DAY_5 0x02000b 11 11 10 10 0
syscon misc DAY_6 0x02000c 12 12 11 11 0
syscon misc DAY_7 0x02000d 13 13 12 12 0
syscon misc FUTEX_PRIVATE_FLAG 0 0 0 0x80 0x80 0
syscon misc FUTEX_REQUEUE 0 0 0 3 3 0
syscon misc FUTEX_REQUEUE_PRIVATE 0 0 0 131 131 0
syscon misc FUTEX_PRIVATE_FLAG 128 0 0 0x80 0x80 0
syscon misc FUTEX_REQUEUE 3 0 0 3 3 0
syscon misc FUTEX_REQUEUE_PRIVATE 131 0 0 131 131 0
syscon misc FUTEX_WAIT 0 0 0 1 1 0
syscon misc FUTEX_WAIT_PRIVATE 0 0 0 129 129 0
syscon misc FUTEX_WAKE 0 0 0 2 2 0
syscon misc FUTEX_WAKE_PRIVATE 0 0 0 130 130 0
syscon misc FUTEX_WAIT_PRIVATE 128 0 0 129 129 0
syscon misc FUTEX_WAKE 1 0 0 2 2 0
syscon misc FUTEX_WAKE_PRIVATE 129 0 0 130 130 0
syscon misc HOST_NOT_FOUND 1 1 1 1 1 0x2af9 # unix consensus
syscon misc HOST_NAME_MAX 0x40 0 0 255 255 0

2
libc/sysv/consts/FUTEX_PRIVATE_FLAG.S
View file

@ -1,2 +1,2 @@
#include "libc/sysv/consts/syscon.internal.h"
.syscon misc,FUTEX_PRIVATE_FLAG,0,0,0,0x80,0x80,0
.syscon misc,FUTEX_PRIVATE_FLAG,128,0,0,0x80,0x80,0

2
libc/sysv/consts/FUTEX_REQUEUE.S
View file

@ -1,2 +1,2 @@
#include "libc/sysv/consts/syscon.internal.h"
.syscon misc,FUTEX_REQUEUE,0,0,0,3,3,0
.syscon misc,FUTEX_REQUEUE,3,0,0,3,3,0

2
libc/sysv/consts/FUTEX_REQUEUE_PRIVATE.S
View file

@ -1,2 +1,2 @@
#include "libc/sysv/consts/syscon.internal.h"
.syscon misc,FUTEX_REQUEUE_PRIVATE,0,0,0,131,131,0
.syscon misc,FUTEX_REQUEUE_PRIVATE,131,0,0,131,131,0

2
libc/sysv/consts/FUTEX_WAIT_PRIVATE.S
View file

@ -1,2 +1,2 @@
#include "libc/sysv/consts/syscon.internal.h"
.syscon misc,FUTEX_WAIT_PRIVATE,0,0,0,129,129,0
.syscon misc,FUTEX_WAIT_PRIVATE,128,0,0,129,129,0

2
libc/sysv/consts/FUTEX_WAKE.S
View file

@ -1,2 +1,2 @@
#include "libc/sysv/consts/syscon.internal.h"
.syscon misc,FUTEX_WAKE,0,0,0,2,2,0
.syscon misc,FUTEX_WAKE,1,0,0,2,2,0

2
libc/sysv/consts/FUTEX_WAKE_PRIVATE.S
View file

@ -1,2 +1,2 @@
#include "libc/sysv/consts/syscon.internal.h"
.syscon misc,FUTEX_WAKE_PRIVATE,0,0,0,130,130,0
.syscon misc,FUTEX_WAKE_PRIVATE,129,0,0,130,130,0

1
libc/thread/join.h
View file

@ -13,4 +13,3 @@ int cthread_join(cthread_t, int*);
COSMOPOLITAN_C_END_
#endif /* !(__ASSEMBLER__ + __LINKER__ + 0) */
#endif /* COSMOPOLITAN_LIBC_THREAD_JOIN_H_ */

112
libc/thread/nativesem.c Normal file
View file

@ -0,0 +1,112 @@
/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8 :vi│
╞══════════════════════════════════════════════════════════════════════════════╡
│ Copyright 2020 Justine Alexandra Roberts Tunney │
│ │
│ Permission to use, copy, modify, and/or distribute this software for │
│ any purpose with or without fee is hereby granted, provided that the │
│ above copyright notice and this permission notice appear in all copies. │
│ │
│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL │
│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED │
│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE │
│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL │
│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR │
│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER │
│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR │
│ PERFORMANCE OF THIS SOFTWARE. │
╚─────────────────────────────────────────────────────────────────────────────*/
#include "libc/thread/nativesem.h"
#include "libc/thread/yield.h"
#include "libc/sysv/consts/nr.h"
#include "libc/sysv/consts/futex.h"
#include "libc/bits/atomic.h"
#define CTHREAD_THREAD_VAL_BITS 32
int cthread_native_sem_init(cthread_native_sem_t* sem, int count) {
sem->linux.count = count;
return 0;
}
int cthread_native_sem_destroy(cthread_native_sem_t* sem) {
(void)sem;
return 0;
}
int cthread_native_sem_signal(cthread_native_sem_t* sem) {
uint64_t count;
asm volatile("lock xadd\t%1, %0" : "+m"(sem->linux.count), "=r"(count) : "1"(1) : "cc");
if ((count >> CTHREAD_THREAD_VAL_BITS)) {
int flags = FUTEX_WAKE;
// WARNING: an offset of 4 bytes would be required on little-endian archs
void* wait_address = &sem->linux.count;
asm volatile (
"syscall"
:
: "a"(__NR_futex), "D"(wait_address), "S"(flags), "d"(1)
: "rcx", "r11", "cc", "memory"
);
}
return 0;
}
int cthread_native_sem_wait_slow(cthread_native_sem_t* sem, const struct timespec* timeout) {
uint64_t count;
// record current thread as waiter
asm volatile("lock xadd\t%1, %0" : "+m"(sem->linux.count), "=r"(count) : "1"((uint64_t)1 << CTHREAD_THREAD_VAL_BITS) : "cc");
for (;;) {
// try to acquire the semaphore, as well as remove itself from waiters
if ((uint32_t)count > 0 && atomic_compare_exchange_weak(&sem->linux.count, count, count - 1 - ((uint64_t)1 << CTHREAD_THREAD_VAL_BITS))) break;
int flags = FUTEX_WAIT;
register struct timespec* timeout_ asm("r10") = timeout;
// WARNING: an offset of 4 bytes would be required on little-endian archs
void* wait_address = &sem->linux.count;
asm volatile (
"syscall"
:
: "a"(__NR_futex), "D"(wait_address), "S"(flags), "d"(count), "r"(timeout_)
: "rcx", "r11", "cc", "memory"
);
count = atomic_load(&sem->linux.count);
}
return 0;
}
int cthread_native_sem_wait_spin_yield(cthread_native_sem_t* sem, uint64_t count, int yield, const struct timespec* timeout) {
// spin on yield
while (yield-- > 0) {
if ((count >> CTHREAD_THREAD_VAL_BITS) != 0) break; // a thread is already waiting in queue
if ((uint32_t)count > 0 && atomic_compare_exchange_weak(&sem->linux.count, count, count-1)) return 0;
cthread_yield();
}
return cthread_native_sem_wait_slow(sem, timeout);
}
int cthread_native_sem_wait_spin(cthread_native_sem_t* sem, uint64_t count, int spin, int yield, const struct timespec* timeout) {
// spin on pause
while (spin-- > 0) {
if ((count >> CTHREAD_THREAD_VAL_BITS) != 0) break;
if ((uint32_t)count > 0 && atomic_compare_exchange_weak(&sem->linux.count, count, count-1)) return 0;
asm volatile ("pause");
}
return cthread_native_sem_wait_spin_yield(sem, count, yield, timeout);
}
int cthread_native_sem_wait(cthread_native_sem_t* sem, int spin, int yield, const struct timespec* timeout) {
uint64_t count = atomic_load(&sem->linux.count);
// uncontended
if ((count >> 32) == 0 && (uint32_t)count > 0 && atomic_compare_exchange_weak(&sem->linux.count, count, count-1)) return 0;
return cthread_native_sem_wait_spin(sem, count, spin, yield, timeout);
}

28
libc/thread/nativesem.h Normal file
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@ -0,0 +1,28 @@
#ifndef COSMOPOLITAN_LIBC_THREAD_NATIVESEM_H_
#define COSMOPOLITAN_LIBC_THREAD_NATIVESEM_H_
#if !(__ASSEMBLER__ + __LINKER__ + 0)
COSMOPOLITAN_C_START_
/**
* @fileoverview native semaphore for implementation details
*/
typedef union cthread_native_sem_t {
struct {
uint64_t count;
} linux;
} cthread_native_sem_t;
struct timespec;
int cthread_native_sem_init(cthread_native_sem_t*, int);
int cthread_native_sem_destroy(cthread_native_sem_t*);
int cthread_native_sem_wait(cthread_native_sem_t*, int, int, const struct timespec*);
int cthread_native_sem_signal(cthread_native_sem_t*);
COSMOPOLITAN_C_END_
#endif /* !(__ASSEMBLER__ + __LINKER__ + 0) */
#endif /* COSMOPOLITAN_LIBC_THREAD_SELF_H_ */

24
libc/thread/yield.c Normal file
View file

@ -0,0 +1,24 @@
/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8 :vi│
╞══════════════════════════════════════════════════════════════════════════════╡
│ Copyright 2020 Justine Alexandra Roberts Tunney │
│ │
│ Permission to use, copy, modify, and/or distribute this software for │
│ any purpose with or without fee is hereby granted, provided that the │
│ above copyright notice and this permission notice appear in all copies. │
│ │
│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL │
│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED │
│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE │
│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL │
│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR │
│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER │
│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR │
│ PERFORMANCE OF THIS SOFTWARE. │
╚─────────────────────────────────────────────────────────────────────────────*/
#include "libc/thread/yield.h"
#include "libc/calls/calls.h"
int cthread_yield(void) {
return sched_yield();
}

14
libc/thread/yield.h Normal file
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@ -0,0 +1,14 @@
#ifndef COSMOPOLITAN_LIBC_THREAD_YIELD_H_
#define COSMOPOLITAN_LIBC_THREAD_YIELD_H_
#if !(__ASSEMBLER__ + __LINKER__ + 0)
COSMOPOLITAN_C_START_
/**
* @fileoverview yield thread to OS scheduler
*/
int cthread_yield(void);
COSMOPOLITAN_C_END_
#endif /* !(__ASSEMBLER__ + __LINKER__ + 0) */
#endif /* COSMOPOLITAN_LIBC_THREAD_YIELD_H_ */