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ipc,sem: fix semctl(..., GETZCNT)

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The semctl GETZCNT returns the number of semops waiting for the
specified semaphore to become zero.  After commit 9f1bc2c902
("ipc,sem: have only one list in struct sem_queue"), the semops waiting
on just one semaphore are waiting on that semaphore's list.

In order to return the correct count, we have to walk that list too, in
addition to the sem_array's list for complex operations.

This bug broke dbench; it works again with this patch applied.

Signed-off-by: Rik van Riel <riel@redhat.com>
Reported-by: Kent Overstreet <koverstreet@google.com>
Tested-by: Kent Overstreet <koverstreet@google.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Rik van Riel 2013-05-09 16:53:28 -04:00 committed by Linus Torvalds
parent 07e074503e
commit ebc2e5e6a4
1 changed files with 7 additions and 0 deletions
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7
ipc/sem.c
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@ -815,6 +815,13 @@ static int count_semzcnt (struct sem_array * sma, ushort semnum)
struct sem_queue * q;
semzcnt = 0;
list_for_each_entry(q, &sma->sem_base[semnum].sem_pending, list) {
struct sembuf * sops = q->sops;
BUG_ON(sops->sem_num != semnum);
if ((sops->sem_op == 0) && !(sops->sem_flg & IPC_NOWAIT))
semzcnt++;
}
list_for_each_entry(q, &sma->sem_pending, list) {
struct sembuf * sops = q->sops;
int nsops = q->nsops;