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LibC: Add futex_wait() and futex_wake() helpers

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These are convinient wrappers over the most used futex operations.
futex_wait() also does some smarts for timeout and clock handling.

Use the new futex_wait() instead of a similar private helper in
LibPthread.
This commit is contained in:
Sergey Bugaev 2021-07-05 14:24:40 +03:00 • committed by Andreas Kling
parent a482a3e609
commit 8fee93d868
2 changed files with 26 additions and 15 deletions
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22
Userland/Libraries/LibC/serenity.h
View file

@ -7,7 +7,9 @@
#pragma once #pragma once
#include <stdio.h> #include <stdio.h>
#include <sys/cdefs.h>
#include <sys/types.h> #include <sys/types.h>
#include <time.h>
#include <unistd.h> #include <unistd.h>
__BEGIN_DECLS __BEGIN_DECLS
@ -70,6 +72,26 @@ int profiling_free_buffer(pid_t);
int futex(uint32_t* userspace_address, int futex_op, uint32_t value, const struct timespec* timeout, uint32_t* userspace_address2, uint32_t value3); int futex(uint32_t* userspace_address, int futex_op, uint32_t value, const struct timespec* timeout, uint32_t* userspace_address2, uint32_t value3);
static ALWAYS_INLINE int futex_wait(uint32_t* userspace_address, uint32_t value, const struct timespec* abstime, int clockid)
{
int op;
if (abstime) {
// NOTE: FUTEX_WAIT takes a relative timeout, so use FUTEX_WAIT_BITSET instead!
op = FUTEX_WAIT_BITSET | FUTEX_PRIVATE_FLAG;
if (clockid == CLOCK_REALTIME || clockid == CLOCK_REALTIME_COARSE)
op |= FUTEX_CLOCK_REALTIME;
} else {
op = FUTEX_WAIT;
}
return futex(userspace_address, op, value, abstime, nullptr, FUTEX_BITSET_MATCH_ANY);
}
static ALWAYS_INLINE int futex_wake(uint32_t* userspace_address, uint32_t count)
{
return futex(userspace_address, FUTEX_WAKE, count, NULL, NULL, 0);
}
#define PURGE_ALL_VOLATILE 0x1 #define PURGE_ALL_VOLATILE 0x1
#define PURGE_ALL_CLEAN_INODE 0x2 #define PURGE_ALL_CLEAN_INODE 0x2

19
Userland/Libraries/LibPthread/pthread.cpp
View file

@ -458,27 +458,16 @@ int pthread_cond_destroy(pthread_cond_t*)
return 0; return 0;
} }
static int futex_wait(uint32_t& futex_addr, uint32_t value, const struct timespec* abstime)
{
int saved_errno = errno;
// NOTE: FUTEX_WAIT takes a relative timeout, so use FUTEX_WAIT_BITSET instead!
int rc = futex(&futex_addr, FUTEX_WAIT_BITSET | FUTEX_CLOCK_REALTIME, value, abstime, nullptr, FUTEX_BITSET_MATCH_ANY);
if (rc < 0 && errno == EAGAIN) {
// If we didn't wait, that's not an error
errno = saved_errno;
rc = 0;
}
return rc;
}
static int cond_wait(pthread_cond_t* cond, pthread_mutex_t* mutex, const struct timespec* abstime) static int cond_wait(pthread_cond_t* cond, pthread_mutex_t* mutex, const struct timespec* abstime)
{ {
u32 value = cond->value; u32 value = cond->value;
cond->previous = value; cond->previous = value;
pthread_mutex_unlock(mutex); pthread_mutex_unlock(mutex);
int rc = futex_wait(cond->value, value, abstime); int rc = futex_wait(&cond->value, value, abstime, cond->clockid);
pthread_mutex_lock(mutex); pthread_mutex_lock(mutex);
return rc; if (rc < 0 && errno != EAGAIN)
return errno;
return 0;
} }
int pthread_cond_wait(pthread_cond_t* cond, pthread_mutex_t* mutex) int pthread_cond_wait(pthread_cond_t* cond, pthread_mutex_t* mutex)