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
key_t key = params->key;
int nsems = params->u.nsems;
int semflg = params->flg;
+ int i;
if (!nsems)
return -EINVAL;
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;
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;
}
}
/* 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 */
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) {
default:
return -EINVAL;
}
- return err;
out_unlock:
sem_unlock(sma);
return err;
}
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;
}
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;
}
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
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;
}
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;
*/
if (timeout && jiffies_left == 0)
error = -EAGAIN;
- list_del(&queue.list);
+ unlink_queue(sma, &queue);
out_unlock_free:
sem_unlock(sma);
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.
}
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);
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,
projects / linux-flexiantxendom0-3.2.10.git / commitdiff