I think this makes sem_init(pshared) work.
I have a test program from Lauri Tirkkonen and if I've understood it
correctly, it works now.
The essence of the diff is that we must eliminate the indirection so that
the application can properly allocate (mmap) the semaphore into shared memory.
There's two variations of the semaphore code (futex and compat). I tested the
compat on amd64, and think it works. The futex version also seems to work,
although I'm not sure how...
Index: rthread.h
===================================================================
RCS file: /home/cvs/src/lib/librthread/rthread.h,v
retrieving revision 1.64
diff -u -p -r1.64 rthread.h
--- rthread.h 13 Feb 2019 13:22:14 -0000 1.64
+++ rthread.h 8 Jul 2020 08:51:08 -0000
@@ -79,8 +79,8 @@ struct pthread_spinlock {
(((size) + (_thread_pagesize - 1)) & ~(_thread_pagesize - 1))
__BEGIN_HIDDEN_DECLS
-int _sem_wait(sem_t, int, const struct timespec *, int *);
-int _sem_post(sem_t);
+int _sem_wait(sem_t *, int, const struct timespec *, int *);
+int _sem_post(sem_t *);
void _rthread_init(void);
struct stack *_rthread_alloc_stack(pthread_t);
Index: rthread_sem.c
===================================================================
RCS file: /home/cvs/src/lib/librthread/rthread_sem.c,v
retrieving revision 1.32
diff -u -p -r1.32 rthread_sem.c
--- rthread_sem.c 6 Apr 2020 00:01:08 -0000 1.32
+++ rthread_sem.c 8 Jul 2020 08:58:07 -0000
@@ -55,7 +55,7 @@
* Internal implementation of semaphores
*/
int
-_sem_wait(sem_t sem, int can_eintr, const struct timespec *abstime,
+_sem_wait(sem_t *sem, int can_eintr, const struct timespec *abstime,
int *delayed_cancel)
{
unsigned int val;
@@ -86,7 +86,7 @@ _sem_wait(sem_t sem, int can_eintr, cons
/* always increment count */
int
-_sem_post(sem_t sem)
+_sem_post(sem_t *sem)
{
membar_exit_before_atomic();
atomic_inc_int(&sem->value);
@@ -98,70 +98,29 @@ _sem_post(sem_t sem)
* exported semaphores
*/
int
-sem_init(sem_t *semp, int pshared, unsigned int value)
+sem_init(sem_t *sem, int pshared, unsigned int value)
{
- sem_t sem;
if (value > SEM_VALUE_MAX) {
errno = EINVAL;
return (-1);
}
- if (pshared) {
- errno = EPERM;
- return (-1);
-#ifdef notyet
- char name[SEM_RANDOM_NAME_LEN];
- sem_t *sempshared;
- int i;
-
- for (;;) {
- for (i = 0; i < SEM_RANDOM_NAME_LEN - 1; i++)
- name[i] = arc4random_uniform(255) + 1;
- name[SEM_RANDOM_NAME_LEN - 1] = '\0';
- sempshared = sem_open(name, O_CREAT | O_EXCL, 0, value);
- if (sempshared != SEM_FAILED)
- break;
- if (errno == EEXIST)
- continue;
- if (errno != EPERM)
- errno = ENOSPC;
- return (-1);
- }
-
- /* unnamed semaphore should not be opened twice */
- if (sem_unlink(name) == -1) {
- sem_close(sempshared);
- errno = ENOSPC;
- return (-1);
- }
-
- *semp = *sempshared;
- free(sempshared);
- return (0);
-#endif
- }
-
- sem = calloc(1, sizeof(*sem));
- if (!sem) {
- errno = ENOSPC;
- return (-1);
- }
+ memset(sem, 0, sizeof(*sem));
sem->value = value;
- *semp = sem;
+ sem->shared = pshared;
return (0);
}
int
-sem_destroy(sem_t *semp)
+sem_destroy(sem_t *sem)
{
- sem_t sem;
if (!_threads_ready) /* for SEM_MMAP_SIZE */
_rthread_init();
- if (!semp || !(sem = *semp)) {
+ if (!sem) {
errno = EINVAL;
return (-1);
}
@@ -174,21 +133,19 @@ sem_destroy(sem_t *semp)
return (-1);
}
- *semp = NULL;
if (sem->shared)
munmap(sem, SEM_MMAP_SIZE);
else
- free(sem);
+ memset(sem, 0, sizeof(*sem));
return (0);
}
int
-sem_getvalue(sem_t *semp, int *sval)
+sem_getvalue(sem_t *sem, int *sval)
{
- sem_t sem;
- if (!semp || !(sem = *semp)) {
+ if (!sem) {
errno = EINVAL;
return (-1);
}
@@ -199,11 +156,10 @@ sem_getvalue(sem_t *semp, int *sval)
}
int
-sem_post(sem_t *semp)
+sem_post(sem_t *sem)
{
- sem_t sem;
- if (!semp || !(sem = *semp)) {
+ if (!sem) {
errno = EINVAL;
return (-1);
}
@@ -214,11 +170,10 @@ sem_post(sem_t *semp)
}
int
-sem_wait(sem_t *semp)
+sem_wait(sem_t *sem)
{
struct tib *tib = TIB_GET();
pthread_t self;
- sem_t sem;
int error;
PREP_CANCEL_POINT(tib);
@@ -226,7 +181,7 @@ sem_wait(sem_t *semp)
_rthread_init();
self = tib->tib_thread;
- if (!semp || !(sem = *semp)) {
+ if (!sem) {
errno = EINVAL;
return (-1);
}
@@ -246,15 +201,14 @@ sem_wait(sem_t *semp)
}
int
-sem_timedwait(sem_t *semp, const struct timespec *abstime)
+sem_timedwait(sem_t *sem, const struct timespec *abstime)
{
struct tib *tib = TIB_GET();
pthread_t self;
- sem_t sem;
int error;
PREP_CANCEL_POINT(tib);
- if (!semp || !(sem = *semp) || abstime == NULL ||
+ if (!sem || abstime == NULL ||
abstime->tv_nsec < 0 || abstime->tv_nsec >= 1000000000) {
errno = EINVAL;
return (-1);
@@ -279,12 +233,11 @@ sem_timedwait(sem_t *semp, const struct
}
int
-sem_trywait(sem_t *semp)
+sem_trywait(sem_t *sem)
{
- sem_t sem;
unsigned int val;
- if (!semp || !(sem = *semp)) {
+ if (!sem) {
errno = EINVAL;
return (-1);
}
@@ -316,7 +269,7 @@ sem_open(const char *name, int oflag, ..
{
char sempath[SEM_PATH_SIZE];
struct stat sb;
- sem_t sem, *semp;
+ sem_t *sem;
unsigned int value = 0;
int created = 0, fd;
@@ -382,34 +335,24 @@ sem_open(const char *name, int oflag, ..
errno = EINVAL;
return (SEM_FAILED);
}
- semp = malloc(sizeof(*semp));
- if (!semp) {
- munmap(sem, SEM_MMAP_SIZE);
- errno = ENOSPC;
- return (SEM_FAILED);
- }
if (created) {
sem->value = value;
sem->shared = 1;
}
- *semp = sem;
- return (semp);
+ return (sem);
}
int
-sem_close(sem_t *semp)
+sem_close(sem_t *sem)
{
- sem_t sem;
- if (!semp || !(sem = *semp) || !sem->shared) {
+ if (!sem) {
errno = EINVAL;
return (-1);
}
- *semp = NULL;
munmap(sem, SEM_MMAP_SIZE);
- free(semp);
return (0);
}
Index: rthread_sem_compat.c
===================================================================
RCS file: /home/cvs/src/lib/librthread/rthread_sem_compat.c,v
retrieving revision 1.1
diff -u -p -r1.1 rthread_sem_compat.c
--- rthread_sem_compat.c 8 Jun 2018 13:53:01 -0000 1.1
+++ rthread_sem_compat.c 8 Jul 2020 09:04:22 -0000
@@ -53,7 +53,7 @@
* Internal implementation of semaphores
*/
int
-_sem_wait(sem_t sem, int can_eintr, const struct timespec *abstime,
+_sem_wait(sem_t *sem, int can_eintr, const struct timespec *abstime,
int *delayed_cancel)
{
void *ident = (void *)&sem->waitcount;
@@ -87,7 +87,7 @@ _sem_wait(sem_t sem, int can_eintr, cons
/* always increment count */
int
-_sem_post(sem_t sem)
+_sem_post(sem_t *sem)
{
void *ident = (void *)&sem->waitcount;
int rv = 0;
@@ -109,71 +109,31 @@ _sem_post(sem_t sem)
* exported semaphores
*/
int
-sem_init(sem_t *semp, int pshared, unsigned int value)
+sem_init(sem_t *sem, int pshared, unsigned int value)
{
- sem_t sem;
if (value > SEM_VALUE_MAX) {
errno = EINVAL;
return (-1);
}
- if (pshared) {
- errno = EPERM;
- return (-1);
-#ifdef notyet
- char name[SEM_RANDOM_NAME_LEN];
- sem_t *sempshared;
- int i;
-
- for (;;) {
- for (i = 0; i < SEM_RANDOM_NAME_LEN - 1; i++)
- name[i] = arc4random_uniform(255) + 1;
- name[SEM_RANDOM_NAME_LEN - 1] = '\0';
- sempshared = sem_open(name, O_CREAT | O_EXCL, 0, value);
- if (sempshared != SEM_FAILED)
- break;
- if (errno == EEXIST)
- continue;
- if (errno != EPERM)
- errno = ENOSPC;
- return (-1);
- }
-
- /* unnamed semaphore should not be opened twice */
- if (sem_unlink(name) == -1) {
- sem_close(sempshared);
- errno = ENOSPC;
- return (-1);
- }
- *semp = *sempshared;
- free(sempshared);
- return (0);
-#endif
- }
-
- sem = calloc(1, sizeof(*sem));
- if (!sem) {
- errno = ENOSPC;
- return (-1);
- }
+ memset(sem, 0, sizeof(*sem));
sem->lock = _SPINLOCK_UNLOCKED;
sem->value = value;
- *semp = sem;
+ sem->shared = pshared;
return (0);
}
int
-sem_destroy(sem_t *semp)
+sem_destroy(sem_t *sem)
{
- sem_t sem;
if (!_threads_ready) /* for SEM_MMAP_SIZE */
_rthread_init();
- if (!semp || !(sem = *semp)) {
+ if (!sem) {
errno = EINVAL;
return (-1);
}
@@ -186,21 +146,17 @@ sem_destroy(sem_t *semp)
return (-1);
}
- *semp = NULL;
if (sem->shared)
munmap(sem, SEM_MMAP_SIZE);
- else
- free(sem);
return (0);
}
int
-sem_getvalue(sem_t *semp, int *sval)
+sem_getvalue(sem_t *sem, int *sval)
{
- sem_t sem;
- if (!semp || !(sem = *semp)) {
+ if (!sem) {
errno = EINVAL;
return (-1);
}
@@ -213,11 +169,10 @@ sem_getvalue(sem_t *semp, int *sval)
}
int
-sem_post(sem_t *semp)
+sem_post(sem_t *sem)
{
- sem_t sem;
- if (!semp || !(sem = *semp)) {
+ if (!sem) {
errno = EINVAL;
return (-1);
}
@@ -228,11 +183,10 @@ sem_post(sem_t *semp)
}
int
-sem_wait(sem_t *semp)
+sem_wait(sem_t *sem)
{
struct tib *tib = TIB_GET();
pthread_t self;
- sem_t sem;
int r;
PREP_CANCEL_POINT(tib);
@@ -240,7 +194,7 @@ sem_wait(sem_t *semp)
_rthread_init();
self = tib->tib_thread;
- if (!semp || !(sem = *semp)) {
+ if (!sem) {
errno = EINVAL;
return (-1);
}
@@ -258,15 +212,14 @@ sem_wait(sem_t *semp)
}
int
-sem_timedwait(sem_t *semp, const struct timespec *abstime)
+sem_timedwait(sem_t *sem, const struct timespec *abstime)
{
struct tib *tib = TIB_GET();
pthread_t self;
- sem_t sem;
int r;
PREP_CANCEL_POINT(tib);
- if (!semp || !(sem = *semp) || abstime == NULL ||
+ if (!sem || abstime == NULL ||
abstime->tv_nsec < 0 || abstime->tv_nsec >= 1000000000) {
errno = EINVAL;
return (-1);
@@ -289,12 +242,11 @@ sem_timedwait(sem_t *semp, const struct
}
int
-sem_trywait(sem_t *semp)
+sem_trywait(sem_t *sem)
{
- sem_t sem;
int r;
- if (!semp || !(sem = *semp)) {
+ if (!sem) {
errno = EINVAL;
return (-1);
}
@@ -330,7 +282,7 @@ sem_open(const char *name, int oflag, ..
{
char sempath[SEM_PATH_SIZE];
struct stat sb;
- sem_t sem, *semp;
+ sem_t *sem;
unsigned int value = 0;
int created = 0, fd;
@@ -396,35 +348,25 @@ sem_open(const char *name, int oflag, ..
errno = EINVAL;
return (SEM_FAILED);
}
- semp = malloc(sizeof(*semp));
- if (!semp) {
- munmap(sem, SEM_MMAP_SIZE);
- errno = ENOSPC;
- return (SEM_FAILED);
- }
if (created) {
sem->lock = _SPINLOCK_UNLOCKED;
sem->value = value;
sem->shared = 1;
}
- *semp = sem;
- return (semp);
+ return (sem);
}
int
-sem_close(sem_t *semp)
+sem_close(sem_t *sem)
{
- sem_t sem;
- if (!semp || !(sem = *semp) || !sem->shared) {
+ if (!sem || !sem->shared) {
errno = EINVAL;
return (-1);
}
- *semp = NULL;
munmap(sem, SEM_MMAP_SIZE);
- free(semp);
return (0);
}
