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-rw-r--r--ipc/sem.c51
1 files changed, 40 insertions, 11 deletions
diff --git a/ipc/sem.c b/ipc/sem.c
index 4252a8eb77e..7eb6f049dd7 100644
--- a/ipc/sem.c
+++ b/ipc/sem.c
@@ -434,17 +434,45 @@ static void unlink_queue(struct sem_array *sma, struct sem_queue *q)
sma->complex_count--;
}
-/* Go through the pending queue for the indicated semaphore
- * looking for tasks that can be completed.
+
+/**
+ * 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)
+static void update_queue(struct sem_array *sma, int semnum)
{
- struct sem_queue *q, *tq;
+ 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:
- list_for_each_entry_safe(q, tq, &sma->sem_pending, list) {
- int error;
- int alter;
+ walk = pending_list->next;
+ while (walk != pending_list) {
+ int error, alter;
+
+ q = (struct sem_queue *)((char *)walk - offset);
+ walk = walk->next;
error = try_atomic_semop(sma, q->sops, q->nsops,
q->undo, q->pid);
@@ -769,7 +797,7 @@ 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;
}
@@ -811,7 +839,7 @@ 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;
}
@@ -1187,7 +1215,8 @@ 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;
}
@@ -1388,7 +1417,7 @@ 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);