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Commit 79ccf0f8 authored by Davidlohr Bueso's avatar Davidlohr Bueso Committed by Linus Torvalds
Browse files

ipc,shm: shorten critical region in shmctl_down 



Instead of holding the ipc lock for the entire function, use the
ipcctl_pre_down_nolock and only acquire the lock for specific commands:
RMID and SET.

Signed-off-by: default avatarDavidlohr Bueso <davidlohr.bueso@hp.com>
Tested-by: default avatarSedat Dilek <sedat.dilek@gmail.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Manfred Spraul <manfred@colorfullife.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 8b8d52ac

ipc/shm.c

+6 −4
Original line number Diff line number Diff line
@@ -780,11 +780,10 @@ static int shmctl_down(struct ipc_namespace *ns, int shmid, int cmd, 
	down_write(&shm_ids(ns).rw_mutex);

	rcu_read_lock();



	ipcp = ipcctl_pre_down(ns, &shm_ids(ns), shmid, cmd,

	ipcp = ipcctl_pre_down_nolock(ns, &shm_ids(ns), shmid, cmd,

				      &shmid64.shm_perm, 0);

	if (IS_ERR(ipcp)) {

		err = PTR_ERR(ipcp);

		/* the ipc lock is not held upon failure */

		goto out_unlock1;

	}
@@ -792,14 +791,16 @@ static int shmctl_down(struct ipc_namespace *ns, int shmid, int cmd, 


	err = security_shm_shmctl(shp, cmd);

	if (err)

		goto out_unlock0;

		goto out_unlock1;



	switch (cmd) {

	case IPC_RMID:

		ipc_lock_object(&shp->shm_perm);

		/* do_shm_rmid unlocks the ipc object and rcu */

		do_shm_rmid(ns, ipcp);

		goto out_up;

	case IPC_SET:

		ipc_lock_object(&shp->shm_perm);

		err = ipc_update_perm(&shmid64.shm_perm, ipcp);

		if (err)

			goto out_unlock0;
@@ -807,6 +808,7 @@ static int shmctl_down(struct ipc_namespace *ns, int shmid, int cmd, 
		break;

	default:

		err = -EINVAL;

		goto out_unlock1;

	}



out_unlock0: