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-rw-r--r--ipc/sem.c128
1 files changed, 88 insertions, 40 deletions
diff --git a/ipc/sem.c b/ipc/sem.c
index 4d7f88cefada..6291257ee049 100644
--- a/ipc/sem.c
+++ b/ipc/sem.c
@@ -192,6 +192,53 @@ void __init sem_init (void)
192 IPC_SEM_IDS, sysvipc_sem_proc_show); 192 IPC_SEM_IDS, sysvipc_sem_proc_show);
193} 193}
194 194
195/**
196 * unmerge_queues - unmerge queues, if possible.
197 * @sma: semaphore array
198 *
199 * The function unmerges the wait queues if complex_count is 0.
200 * It must be called prior to dropping the global semaphore array lock.
201 */
202static void unmerge_queues(struct sem_array *sma)
203{
204 struct sem_queue *q, *tq;
205
206 /* complex operations still around? */
207 if (sma->complex_count)
208 return;
209 /*
210 * We will switch back to simple mode.
211 * Move all pending operation back into the per-semaphore
212 * queues.
213 */
214 list_for_each_entry_safe(q, tq, &sma->pending_alter, list) {
215 struct sem *curr;
216 curr = &sma->sem_base[q->sops[0].sem_num];
217
218 list_add_tail(&q->list, &curr->pending_alter);
219 }
220 INIT_LIST_HEAD(&sma->pending_alter);
221}
222
223/**
224 * merge_queues - Merge single semop queues into global queue
225 * @sma: semaphore array
226 *
227 * This function merges all per-semaphore queues into the global queue.
228 * It is necessary to achieve FIFO ordering for the pending single-sop
229 * operations when a multi-semop operation must sleep.
230 * Only the alter operations must be moved, the const operations can stay.
231 */
232static void merge_queues(struct sem_array *sma)
233{
234 int i;
235 for (i = 0; i < sma->sem_nsems; i++) {
236 struct sem *sem = sma->sem_base + i;
237
238 list_splice_init(&sem->pending_alter, &sma->pending_alter);
239 }
240}
241
195/* 242/*
196 * If the request contains only one semaphore operation, and there are 243 * If the request contains only one semaphore operation, and there are
197 * no complex transactions pending, lock only the semaphore involved. 244 * no complex transactions pending, lock only the semaphore involved.
@@ -262,6 +309,7 @@ static inline int sem_lock(struct sem_array *sma, struct sembuf *sops,
262static inline void sem_unlock(struct sem_array *sma, int locknum) 309static inline void sem_unlock(struct sem_array *sma, int locknum)
263{ 310{
264 if (locknum == -1) { 311 if (locknum == -1) {
312 unmerge_queues(sma);
265 ipc_unlock_object(&sma->sem_perm); 313 ipc_unlock_object(&sma->sem_perm);
266 } else { 314 } else {
267 struct sem *sem = sma->sem_base + locknum; 315 struct sem *sem = sma->sem_base + locknum;
@@ -831,49 +879,38 @@ static void do_smart_update(struct sem_array *sma, struct sembuf *sops, int nsop
831 int otime, struct list_head *pt) 879 int otime, struct list_head *pt)
832{ 880{
833 int i; 881 int i;
834 int progress;
835 882
836 otime |= do_smart_wakeup_zero(sma, sops, nsops, pt); 883 otime |= do_smart_wakeup_zero(sma, sops, nsops, pt);
837 884
838 progress = 1; 885 if (!list_empty(&sma->pending_alter)) {
839retry_global: 886 /* semaphore array uses the global queue - just process it. */
840 if (sma->complex_count) { 887 otime |= update_queue(sma, -1, pt);
841 if (update_queue(sma, -1, pt)) { 888 } else {
842 progress = 1; 889 if (!sops) {
843 otime = 1; 890 /*
844 sops = NULL; 891 * No sops, thus the modified semaphores are not
845 } 892 * known. Check all.
846 } 893 */
847 if (!progress) 894 for (i = 0; i < sma->sem_nsems; i++)
848 goto done; 895 otime |= update_queue(sma, i, pt);
849 896 } else {
850 if (!sops) { 897 /*
851 /* No semops; something special is going on. */ 898 * Check the semaphores that were increased:
852 for (i = 0; i < sma->sem_nsems; i++) { 899 * - No complex ops, thus all sleeping ops are
853 if (update_queue(sma, i, pt)) { 900 * decrease.
854 otime = 1; 901 * - if we decreased the value, then any sleeping
855 progress = 1; 902 * semaphore ops wont be able to run: If the
903 * previous value was too small, then the new
904 * value will be too small, too.
905 */
906 for (i = 0; i < nsops; i++) {
907 if (sops[i].sem_op > 0) {
908 otime |= update_queue(sma,
909 sops[i].sem_num, pt);
910 }
856 } 911 }
857 } 912 }
858 goto done_checkretry;
859 }
860
861 /* Check the semaphores that were modified. */
862 for (i = 0; i < nsops; i++) {
863 if (sops[i].sem_op > 0 ||
864 (sops[i].sem_op < 0 &&
865 sma->sem_base[sops[i].sem_num].semval == 0))
866 if (update_queue(sma, sops[i].sem_num, pt)) {
867 otime = 1;
868 progress = 1;
869 }
870 }
871done_checkretry:
872 if (progress) {
873 progress = 0;
874 goto retry_global;
875 } 913 }
876done:
877 if (otime) 914 if (otime)
878 sma->sem_otime = get_seconds(); 915 sma->sem_otime = get_seconds();
879} 916}
@@ -1747,11 +1784,22 @@ SYSCALL_DEFINE4(semtimedop, int, semid, struct sembuf __user *, tsops,
1747 struct sem *curr; 1784 struct sem *curr;
1748 curr = &sma->sem_base[sops->sem_num]; 1785 curr = &sma->sem_base[sops->sem_num];
1749 1786
1750 if (alter) 1787 if (alter) {
1751 list_add_tail(&queue.list, &curr->pending_alter); 1788 if (sma->complex_count) {
1752 else 1789 list_add_tail(&queue.list,
1790 &sma->pending_alter);
1791 } else {
1792
1793 list_add_tail(&queue.list,
1794 &curr->pending_alter);
1795 }
1796 } else {
1753 list_add_tail(&queue.list, &curr->pending_const); 1797 list_add_tail(&queue.list, &curr->pending_const);
1798 }
1754 } else { 1799 } else {
1800 if (!sma->complex_count)
1801 merge_queues(sma);
1802
1755 if (alter) 1803 if (alter)
1756 list_add_tail(&queue.list, &sma->pending_alter); 1804 list_add_tail(&queue.list, &sma->pending_alter);
1757 else 1805 else