diff options
Diffstat (limited to 'ipc')
| -rw-r--r-- | ipc/msg.c | 1 | ||||
| -rw-r--r-- | ipc/sem.c | 214 | ||||
| -rw-r--r-- | ipc/shm.c | 1 |
3 files changed, 147 insertions, 69 deletions
@@ -125,6 +125,7 @@ void msg_init_ns(struct ipc_namespace *ns) void msg_exit_ns(struct ipc_namespace *ns) { free_ipcs(ns, &msg_ids(ns), freeque); + idr_destroy(&ns->ids[IPC_MSG_IDS].ipcs_idr); } #endif @@ -129,6 +129,7 @@ void sem_init_ns(struct ipc_namespace *ns) void sem_exit_ns(struct ipc_namespace *ns) { free_ipcs(ns, &sem_ids(ns), freeary); + idr_destroy(&ns->ids[IPC_SEM_IDS].ipcs_idr); } #endif @@ -240,6 +241,7 @@ static int newary(struct ipc_namespace *ns, struct ipc_params *params) key_t key = params->key; int nsems = params->u.nsems; int semflg = params->flg; + int i; if (!nsems) return -EINVAL; @@ -272,6 +274,11 @@ static int newary(struct ipc_namespace *ns, struct ipc_params *params) ns->used_sems += nsems; sma->sem_base = (struct sem *) &sma[1]; + + for (i = 0; i < nsems; i++) + INIT_LIST_HEAD(&sma->sem_base[i].sem_pending); + + sma->complex_count = 0; INIT_LIST_HEAD(&sma->sem_pending); INIT_LIST_HEAD(&sma->list_id); sma->sem_nsems = nsems; @@ -397,63 +404,109 @@ undo: return result; } -/* Go through the pending queue for the indicated semaphore - * looking for tasks that can be completed. +/* + * Wake up a process waiting on the sem queue with a given error. + * The queue is invalid (may not be accessed) after the function returns. */ -static void update_queue (struct sem_array * sma) +static void wake_up_sem_queue(struct sem_queue *q, int error) { - int error; - struct sem_queue * q; + /* + * Hold preempt off so that we don't get preempted and have the + * wakee busy-wait until we're scheduled back on. We're holding + * locks here so it may not strictly be needed, however if the + * locks become preemptible then this prevents such a problem. + */ + preempt_disable(); + q->status = IN_WAKEUP; + wake_up_process(q->sleeper); + /* hands-off: q can disappear immediately after writing q->status. */ + smp_wmb(); + q->status = error; + preempt_enable(); +} + +static void unlink_queue(struct sem_array *sma, struct sem_queue *q) +{ + list_del(&q->list); + if (q->nsops == 1) + list_del(&q->simple_list); + else + sma->complex_count--; +} + + +/** + * update_queue(sma, semnum): Look for tasks that can be completed. + * @sma: semaphore array. + * @semnum: semaphore that was modified. + * + * update_queue must be called after a semaphore in a semaphore array + * was modified. If multiple semaphore were modified, then @semnum + * must be set to -1. + */ +static void update_queue(struct sem_array *sma, int semnum) +{ + struct sem_queue *q; + struct list_head *walk; + struct list_head *pending_list; + int offset; + + /* if there are complex operations around, then knowing the semaphore + * that was modified doesn't help us. Assume that multiple semaphores + * were modified. + */ + if (sma->complex_count) + semnum = -1; + + if (semnum == -1) { + pending_list = &sma->sem_pending; + offset = offsetof(struct sem_queue, list); + } else { + pending_list = &sma->sem_base[semnum].sem_pending; + offset = offsetof(struct sem_queue, simple_list); + } + +again: + walk = pending_list->next; + while (walk != pending_list) { + int error, alter; + + q = (struct sem_queue *)((char *)walk - offset); + walk = walk->next; + + /* If we are scanning the single sop, per-semaphore list of + * one semaphore and that semaphore is 0, then it is not + * necessary to scan the "alter" entries: simple increments + * that affect only one entry succeed immediately and cannot + * be in the per semaphore pending queue, and decrements + * cannot be successful if the value is already 0. + */ + if (semnum != -1 && sma->sem_base[semnum].semval == 0 && + q->alter) + break; - q = list_entry(sma->sem_pending.next, struct sem_queue, list); - while (&q->list != &sma->sem_pending) { error = try_atomic_semop(sma, q->sops, q->nsops, q->undo, q->pid); /* Does q->sleeper still need to sleep? */ - if (error <= 0) { - struct sem_queue *n; - - /* - * Continue scanning. The next operation - * that must be checked depends on the type of the - * completed operation: - * - if the operation modified the array, then - * restart from the head of the queue and - * check for threads that might be waiting - * for semaphore values to become 0. - * - if the operation didn't modify the array, - * then just continue. - * The order of list_del() and reading ->next - * is crucial: In the former case, the list_del() - * must be done first [because we might be the - * first entry in ->sem_pending], in the latter - * case the list_del() must be done last - * [because the list is invalid after the list_del()] - */ - if (q->alter) { - list_del(&q->list); - n = list_entry(sma->sem_pending.next, - struct sem_queue, list); - } else { - n = list_entry(q->list.next, struct sem_queue, - list); - list_del(&q->list); - } - - /* wake up the waiting thread */ - q->status = IN_WAKEUP; + if (error > 0) + continue; - wake_up_process(q->sleeper); - /* hands-off: q will disappear immediately after - * writing q->status. - */ - smp_wmb(); - q->status = error; - q = n; - } else { - q = list_entry(q->list.next, struct sem_queue, list); - } + unlink_queue(sma, q); + + /* + * The next operation that must be checked depends on the type + * of the completed operation: + * - if the operation modified the array, then restart from the + * head of the queue and check for threads that might be + * waiting for the new semaphore values. + * - if the operation didn't modify the array, then just + * continue. + */ + alter = q->alter; + wake_up_sem_queue(q, error); + if (alter && !error) + goto again; } } @@ -533,12 +586,8 @@ static void freeary(struct ipc_namespace *ns, struct kern_ipc_perm *ipcp) /* Wake up all pending processes and let them fail with EIDRM. */ list_for_each_entry_safe(q, tq, &sma->sem_pending, list) { - list_del(&q->list); - - q->status = IN_WAKEUP; - wake_up_process(q->sleeper); /* doesn't sleep */ - smp_wmb(); - q->status = -EIDRM; /* hands-off q */ + unlink_queue(sma, q); + wake_up_sem_queue(q, -EIDRM); } /* Remove the semaphore set from the IDR */ @@ -575,7 +624,7 @@ static unsigned long copy_semid_to_user(void __user *buf, struct semid64_ds *in, static int semctl_nolock(struct ipc_namespace *ns, int semid, int cmd, int version, union semun arg) { - int err = -EINVAL; + int err; struct sem_array *sma; switch(cmd) { @@ -652,7 +701,6 @@ static int semctl_nolock(struct ipc_namespace *ns, int semid, default: return -EINVAL; } - return err; out_unlock: sem_unlock(sma); return err; @@ -759,7 +807,7 @@ static int semctl_main(struct ipc_namespace *ns, int semid, int semnum, } sma->sem_ctime = get_seconds(); /* maybe some queued-up processes were waiting for this */ - update_queue(sma); + update_queue(sma, -1); err = 0; goto out_unlock; } @@ -801,7 +849,7 @@ static int semctl_main(struct ipc_namespace *ns, int semid, int semnum, curr->sempid = task_tgid_vnr(current); sma->sem_ctime = get_seconds(); /* maybe some queued-up processes were waiting for this */ - update_queue(sma); + update_queue(sma, semnum); err = 0; goto out_unlock; } @@ -961,17 +1009,31 @@ static inline int get_undo_list(struct sem_undo_list **undo_listp) return 0; } -static struct sem_undo *lookup_undo(struct sem_undo_list *ulp, int semid) +static struct sem_undo *__lookup_undo(struct sem_undo_list *ulp, int semid) { - struct sem_undo *walk; + struct sem_undo *un; - list_for_each_entry_rcu(walk, &ulp->list_proc, list_proc) { - if (walk->semid == semid) - return walk; + list_for_each_entry_rcu(un, &ulp->list_proc, list_proc) { + if (un->semid == semid) + return un; } return NULL; } +static struct sem_undo *lookup_undo(struct sem_undo_list *ulp, int semid) +{ + struct sem_undo *un; + + assert_spin_locked(&ulp->lock); + + un = __lookup_undo(ulp, semid); + if (un) { + list_del_rcu(&un->list_proc); + list_add_rcu(&un->list_proc, &ulp->list_proc); + } + return un; +} + /** * find_alloc_undo - Lookup (and if not present create) undo array * @ns: namespace @@ -1163,7 +1225,8 @@ SYSCALL_DEFINE4(semtimedop, int, semid, struct sembuf __user *, tsops, error = try_atomic_semop (sma, sops, nsops, un, task_tgid_vnr(current)); if (error <= 0) { if (alter && error == 0) - update_queue (sma); + update_queue(sma, (nsops == 1) ? sops[0].sem_num : -1); + goto out_unlock_free; } @@ -1181,6 +1244,19 @@ SYSCALL_DEFINE4(semtimedop, int, semid, struct sembuf __user *, tsops, else list_add(&queue.list, &sma->sem_pending); + if (nsops == 1) { + struct sem *curr; + curr = &sma->sem_base[sops->sem_num]; + + if (alter) + list_add_tail(&queue.simple_list, &curr->sem_pending); + else + list_add(&queue.simple_list, &curr->sem_pending); + } else { + INIT_LIST_HEAD(&queue.simple_list); + sma->complex_count++; + } + queue.status = -EINTR; queue.sleeper = current; current->state = TASK_INTERRUPTIBLE; @@ -1222,7 +1298,7 @@ SYSCALL_DEFINE4(semtimedop, int, semid, struct sembuf __user *, tsops, */ if (timeout && jiffies_left == 0) error = -EAGAIN; - list_del(&queue.list); + unlink_queue(sma, &queue); out_unlock_free: sem_unlock(sma); @@ -1307,7 +1383,7 @@ void exit_sem(struct task_struct *tsk) if (IS_ERR(sma)) continue; - un = lookup_undo(ulp, semid); + un = __lookup_undo(ulp, semid); if (un == NULL) { /* exit_sem raced with IPC_RMID+semget() that created * exactly the same semid. Nothing to do. @@ -1351,7 +1427,7 @@ void exit_sem(struct task_struct *tsk) } sma->sem_otime = get_seconds(); /* maybe some queued-up processes were waiting for this */ - update_queue(sma); + update_queue(sma, -1); sem_unlock(sma); call_rcu(&un->rcu, free_un); @@ -1365,7 +1441,7 @@ static int sysvipc_sem_proc_show(struct seq_file *s, void *it) struct sem_array *sma = it; return seq_printf(s, - "%10d %10d %4o %10lu %5u %5u %5u %5u %10lu %10lu\n", + "%10d %10d %4o %10u %5u %5u %5u %5u %10lu %10lu\n", sma->sem_perm.key, sma->sem_perm.id, sma->sem_perm.mode, @@ -100,6 +100,7 @@ static void do_shm_rmid(struct ipc_namespace *ns, struct kern_ipc_perm *ipcp) void shm_exit_ns(struct ipc_namespace *ns) { free_ipcs(ns, &shm_ids(ns), do_shm_rmid); + idr_destroy(&ns->ids[IPC_SHM_IDS].ipcs_idr); } #endif |
