ipc: move rcu lock out of ipc_addid (dbfcd91f) · Commits · 戴 / test

This patchset continues the work that began in the sysv ipc semaphore scaling series, see https://lkml.org/lkml/2013/3/20/546 Just like semaphores used to be, sysv shared memory and msg queues also abuse the ipc lock, unnecessarily holding it for operations such as permission and security checks. This patchset mostly deals with mqueues, and while shared mem can be done in a very similar way, I want to get these patches out in the open first. It also does some pending cleanups, mostly focused on the two level locking we have in ipc code, taking care of ipc_addid() and ipcctl_pre_down_nolock() - yes there are still functions that need to be updated as well. This patch: Make all callers explicitly take and release the RCU read lock. This addresses the two level locking seen in newary(), newseg() and newqueue(). For the last two, explicitly unlock the ipc object and the rcu lock, instead of calling the custom shm_unlock and msg_unlock functions. The next patch will deal with the open coded locking for ->perm.lock Signed-off-by:

Davidlohr Bueso <davidlohr.bueso@hp.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: Rik van Riel <riel@redhat.com> Signed-off-by:

Andrew Morton <akpm@linux-foundation.org> Signed-off-by:

Linus Torvalds <torvalds@linux-foundation.org>

ipc/msg.c

+3 −4

Original line number	Diff line number	Diff line
		@@ -199,9 +199,7 @@ static int newque(struct ipc_namespace ns, struct ipc_params params)
		return retval;
		}

		/*
		* ipc_addid() locks msq
		*/
		/* ipc_addid() locks msq upon success. */
		id = ipc_addid(&msg_ids(ns), &msq->q_perm, ns->msg_ctlmni);
		if (id < 0) {
		security_msg_queue_free(msq);
		@@ -218,7 +216,8 @@ static int newque(struct ipc_namespace ns, struct ipc_params params)
		INIT_LIST_HEAD(&msq->q_receivers);
		INIT_LIST_HEAD(&msq->q_senders);

		msg_unlock(msq);
		spin_unlock(&msq->q_perm.lock);
		rcu_read_unlock();

		return msq->q_perm.id;
		}

ipc/shm.c

+4 −1

Original line number	Diff line number	Diff line
		@@ -535,6 +535,7 @@ static int newseg(struct ipc_namespace ns, struct ipc_params params)
		shp->shm_nattch = 0;
		shp->shm_file = file;
		shp->shm_creator = current;

		/*
		* shmid gets reported as "inode#" in /proc/pid/maps.
		* proc-ps tools use this. Changing this will break them.
		@@ -543,7 +544,9 @@ static int newseg(struct ipc_namespace ns, struct ipc_params params)

		ns->shm_tot += numpages;
		error = shp->shm_perm.id;
		shm_unlock(shp);

		spin_unlock(&shp->shm_perm.lock);
		rcu_read_unlock();
		return error;

		no_id:

ipc/util.c

+1 −2

Original line number	Diff line number	Diff line
		@@ -246,9 +246,8 @@ int ipc_get_maxid(struct ipc_ids *ids)
		* is returned. The 'new' entry is returned in a locked state on success.
		* On failure the entry is not locked and a negative err-code is returned.
		*
		* Called with ipc_ids.rw_mutex held as a writer.
		* Called with writer ipc_ids.rw_mutex held.
		*/

		int ipc_addid(struct ipc_ids* ids, struct kern_ipc_perm* new, int size)
		{
		kuid_t euid;

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