1 files changed, 11 insertions, 0 deletions

diff --git a/ipc/sem.c b/ipc/sem.c
index 7eb6f049dd7c..82518d6a96a3 100644
--- a/ipc/sem.c
+++ b/ipc/sem.c
@@ -474,6 +474,17 @@ again:
                 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;
+
                 error = try_atomic_semop(sma, q->sops, q->nsops,
                                          q->undo, q->pid);