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IPC/semaphores: move the rwmutex handling inside semctl_down

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semctl_down is called with the rwmutex (the one which protects the list of
ipcs) taken in write mode.

This patch moves this rwmutex taken in write-mode inside semctl_down.

This has the advantages of reducing a little bit the window during which this
rwmutex is taken, clarifying sys_semctl, and finally of having a coherent
behaviour with [shm|msg]ctl_down

Signed-off-by: Pierre Peiffer <pierre.peiffer@bull.net>
Acked-by: Serge Hallyn <serue@us.ibm.com>
Cc: Nadia Derbey <Nadia.Derbey@bull.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Pierre Peiffer 2008-04-29 01:00:49 -07:00 committed by Linus Torvalds
parent a0d092fc2d
commit 522bb2a2b4
1 changed files with 13 additions and 11 deletions
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24
ipc/sem.c
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@ -875,6 +875,11 @@ static inline unsigned long copy_semid_from_user(struct sem_setbuf *out, void __
}
}
/*
* This function handles some semctl commands which require the rw_mutex
* to be held in write mode.
* NOTE: no locks must be held, the rw_mutex is taken inside this function.
*/
static int semctl_down(struct ipc_namespace *ns, int semid, int semnum,
int cmd, int version, union semun arg)
{
@ -887,9 +892,12 @@ static int semctl_down(struct ipc_namespace *ns, int semid, int semnum,
if(copy_semid_from_user (&setbuf, arg.buf, version))
return -EFAULT;
}
down_write(&sem_ids(ns).rw_mutex);
sma = sem_lock_check_down(ns, semid);
if (IS_ERR(sma))
return PTR_ERR(sma);
if (IS_ERR(sma)) {
err = PTR_ERR(sma);
goto out_up;
}
ipcp = &sma->sem_perm;
@ -915,26 +923,22 @@ static int semctl_down(struct ipc_namespace *ns, int semid, int semnum,
switch(cmd){
case IPC_RMID:
freeary(ns, ipcp);
err = 0;
break;
goto out_up;
case IPC_SET:
ipcp->uid = setbuf.uid;
ipcp->gid = setbuf.gid;
ipcp->mode = (ipcp->mode & ~S_IRWXUGO)
| (setbuf.mode & S_IRWXUGO);
sma->sem_ctime = get_seconds();
sem_unlock(sma);
err = 0;
break;
default:
sem_unlock(sma);
err = -EINVAL;
break;
}
return err;
out_unlock:
sem_unlock(sma);
out_up:
up_write(&sem_ids(ns).rw_mutex);
return err;
}
@ -968,9 +972,7 @@ asmlinkage long sys_semctl (int semid, int semnum, int cmd, union semun arg)
return err;
case IPC_RMID:
case IPC_SET:
down_write(&sem_ids(ns).rw_mutex);
err = semctl_down(ns,semid,semnum,cmd,version,arg);
up_write(&sem_ids(ns).rw_mutex);
return err;
default:
return -EINVAL;