diff options
Diffstat (limited to 'ipc/sem.c')
| -rw-r--r-- | ipc/sem.c | 32 |
1 files changed, 21 insertions, 11 deletions
diff --git a/ipc/sem.c b/ipc/sem.c index 51352e1bfff..41088899783 100644 --- a/ipc/sem.c +++ b/ipc/sem.c @@ -154,12 +154,15 @@ static int sysvipc_sem_proc_show(struct seq_file *s, void *it); #define SEMOPM_FAST 64 /* ~ 372 bytes on stack */ /* - * linked list protection: + * Locking: * sem_undo.id_next, + * sem_array.complex_count, * sem_array.pending{_alter,_cont}, - * sem_array.sem_undo: sem_lock() for read/write + * sem_array.sem_undo: global sem_lock() for read/write * sem_undo.proc_next: only "current" is allowed to read/write that field. * + * sem_array.sem_base[i].pending_{const,alter}: + * global or semaphore sem_lock() for read/write */ #define sc_semmsl sem_ctls[0] @@ -536,12 +539,19 @@ SYSCALL_DEFINE3(semget, key_t, key, int, nsems, int, semflg) return ipcget(ns, &sem_ids(ns), &sem_ops, &sem_params); } -/* - * Determine whether a sequence of semaphore operations would succeed - * all at once. Return 0 if yes, 1 if need to sleep, else return error code. +/** perform_atomic_semop - Perform (if possible) a semaphore operation + * @sma: semaphore array + * @sops: array with operations that should be checked + * @nsems: number of sops + * @un: undo array + * @pid: pid that did the change + * + * Returns 0 if the operation was possible. + * Returns 1 if the operation is impossible, the caller must sleep. + * Negative values are error codes. */ -static int try_atomic_semop (struct sem_array * sma, struct sembuf * sops, +static int perform_atomic_semop(struct sem_array *sma, struct sembuf *sops, int nsops, struct sem_undo *un, int pid) { int result, sem_op; @@ -724,8 +734,8 @@ static int wake_const_ops(struct sem_array *sma, int semnum, q = container_of(walk, struct sem_queue, list); walk = walk->next; - error = try_atomic_semop(sma, q->sops, q->nsops, - q->undo, q->pid); + error = perform_atomic_semop(sma, q->sops, q->nsops, + q->undo, q->pid); if (error <= 0) { /* operation completed, remove from queue & wakeup */ @@ -838,7 +848,7 @@ again: if (semnum != -1 && sma->sem_base[semnum].semval == 0) break; - error = try_atomic_semop(sma, q->sops, q->nsops, + error = perform_atomic_semop(sma, q->sops, q->nsops, q->undo, q->pid); /* Does q->sleeper still need to sleep? */ @@ -1686,7 +1696,6 @@ static int get_queue_result(struct sem_queue *q) return error; } - SYSCALL_DEFINE4(semtimedop, int, semid, struct sembuf __user *, tsops, unsigned, nsops, const struct timespec __user *, timeout) { @@ -1784,7 +1793,8 @@ SYSCALL_DEFINE4(semtimedop, int, semid, struct sembuf __user *, tsops, if (un && un->semid == -1) goto out_unlock_free; - error = try_atomic_semop (sma, sops, nsops, un, task_tgid_vnr(current)); + error = perform_atomic_semop(sma, sops, nsops, un, + task_tgid_vnr(current)); if (error <= 0) { if (alter && error == 0) do_smart_update(sma, sops, nsops, 1, &tasks); |