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LibPthread: Support process-shared semaphores

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This commit is contained in:
Idan Horowitz 2022-07-14 03:07:06 +03:00 committed by Andreas Kling
parent 3f838768d9
commit 35789f56a5
Notes: sideshowbarker 2024-07-17 08:42:17 +09:00 
Author: https://github.com/IdanHo
Commit: https://github.com/SerenityOS/serenity/commit/35789f56a5
Pull-request: https://github.com/SerenityOS/serenity/pull/14578
2 changed files with 8 additions and 9 deletions
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15
Userland/Libraries/LibC/semaphore.cpp
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@ -40,13 +40,8 @@ int sem_unlink(char const*)
}
// https://pubs.opengroup.org/onlinepubs/9699919799/functions/sem_init.html
int sem_init(sem_t* sem, int shared, unsigned int value)
int sem_init(sem_t* sem, int process_shared, unsigned int value)
{
if (shared) {
errno = ENOSYS;
return -1;
}
if (value > SEM_VALUE_MAX) {
errno = EINVAL;
return -1;
@ -54,6 +49,7 @@ int sem_init(sem_t* sem, int shared, unsigned int value)
sem->magic = SEM_MAGIC;
sem->value = value;
sem->flags = process_shared ? SEM_FLAG_PROCESS_SHARED : 0;
return 0;
}
@ -102,7 +98,7 @@ int sem_post(sem_t* sem)
// Check if another sem_post() call has handled it already.
if (!(value & POST_WAKES)) [[likely]]
return 0;
int rc = futex_wake(&sem->value, 1, false);
int rc = futex_wake(&sem->value, 1, sem->flags & SEM_FLAG_PROCESS_SHARED);
VERIFY(rc >= 0);
return 0;
}
@ -153,6 +149,7 @@ int sem_timedwait(sem_t* sem, const struct timespec* abstime)
u32 value = AK::atomic_load(&sem->value, AK::memory_order_relaxed);
bool responsible_for_waking = false;
bool process_shared = sem->flags & SEM_FLAG_PROCESS_SHARED;
while (true) {
u32 count = value & ~POST_WAKES;
@ -179,7 +176,7 @@ int sem_timedwait(sem_t* sem, const struct timespec* abstime)
// Re-evaluate.
continue;
if (going_to_wake) [[unlikely]] {
int rc = futex_wake(&sem->value, count - 1, false);
int rc = futex_wake(&sem->value, count - 1, process_shared);
VERIFY(rc >= 0);
}
return 0;
@ -196,7 +193,7 @@ int sem_timedwait(sem_t* sem, const struct timespec* abstime)
}
// At this point, we're committed to sleeping.
responsible_for_waking = true;
futex_wait(&sem->value, value, abstime, CLOCK_REALTIME, false);
futex_wait(&sem->value, value, abstime, CLOCK_REALTIME, process_shared);
// This is the state we will probably see upon being waked:
value = 1;
}

2
Userland/Libraries/LibC/semaphore.h
View File

@ -13,9 +13,11 @@
__BEGIN_DECLS
#define SEM_FLAG_PROCESS_SHARED (1 << 0)
typedef struct {
uint32_t magic;
uint32_t value;
uint8_t flags;
} sem_t;
int sem_close(sem_t*);