From ab465df9dda42a997f7537c875127eeb6a88158c Mon Sep 17 00:00:00 2001 From: Manfred Spraul Date: Sun, 26 May 2013 11:08:52 +0200 Subject: [PATCH] ipc/sem.c: Fix missing wakeups in do_smart_update_queue() do_smart_update_queue() is called when an operation (semop, semctl(SETVAL), semctl(SETALL), ...) modified the array. It must check which of the sleeping tasks can proceed. do_smart_update_queue() missed a few wakeups: - if a sleeping complex op was completed, then all per-semaphore queues must be scanned - not only those that were modified by *sops - if a sleeping simple op proceeded, then the global queue must be scanned again And: - the test for "|sops == NULL) before scanning the global queue is not required: If the global queue is empty, then it doesn't need to be scanned - regardless of the reason for calling do_smart_update_queue() The patch is not optimized, i.e. even completing a wait-for-zero operation causes a rescan. This is done to keep the patch as simple as possible. Signed-off-by: Manfred Spraul Acked-by: Davidlohr Bueso Cc: Rik van Riel Cc: Andrew Morton Signed-off-by: Linus Torvalds --- ipc/sem.c | 27 ++++++++++++++++++++++----- 1 file changed, 22 insertions(+), 5 deletions(-) diff --git a/ipc/sem.c b/ipc/sem.c index a7e40ed8a076..70480a3aa698 100644 --- a/ipc/sem.c +++ b/ipc/sem.c @@ -752,19 +752,29 @@ static void do_smart_update(struct sem_array *sma, struct sembuf *sops, int nsop int otime, struct list_head *pt) { int i; + int progress; - if (sma->complex_count || sops == NULL) { - if (update_queue(sma, -1, pt)) + progress = 1; +retry_global: + if (sma->complex_count) { + if (update_queue(sma, -1, pt)) { + progress = 1; otime = 1; + sops = NULL; + } } + if (!progress) + goto done; if (!sops) { /* No semops; something special is going on. */ for (i = 0; i < sma->sem_nsems; i++) { - if (update_queue(sma, i, pt)) + if (update_queue(sma, i, pt)) { otime = 1; + progress = 1; + } } - goto done; + goto done_checkretry; } /* Check the semaphores that were modified. */ @@ -772,8 +782,15 @@ static void do_smart_update(struct sem_array *sma, struct sembuf *sops, int nsop if (sops[i].sem_op > 0 || (sops[i].sem_op < 0 && sma->sem_base[sops[i].sem_num].semval == 0)) - if (update_queue(sma, sops[i].sem_num, pt)) + if (update_queue(sma, sops[i].sem_num, pt)) { otime = 1; + progress = 1; + } + } +done_checkretry: + if (progress) { + progress = 0; + goto retry_global; } done: if (otime)