ipc: call idr_find() without locking in ipc_lock() (983bfb7d) · Commits · 戴 / test

Call idr_find() locklessly from ipc_lock(), since the idr tree is now RCU protected. Signed-off-by:

Nadia Derbey <Nadia.Derbey@bull.net> Acked-by:

"Paul E. McKenney" <paulmck@us.ibm.com> Cc: Manfred Spraul <manfred@colorfullife.com> Cc: Jim Houston <jim.houston@comcast.net> Cc: Pierre Peiffer <peifferp@gmail.com> Acked-by:

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/util.c

+0 −9

Original line number	Diff line number	Diff line
		@@ -688,10 +688,6 @@ void ipc64_perm_to_ipc_perm (struct ipc64_perm in, struct ipc_perm out)
		* Look for an id in the ipc ids idr and lock the associated ipc object.
		*
		* The ipc object is locked on exit.
		*
		* This is the routine that should be called when the rw_mutex is not already
		* held, i.e. idr tree not protected: it protects the idr tree in read mode
		* during the idr_find().
		*/

		struct kern_ipc_perm ipc_lock(struct ipc_ids ids, int id)
		@@ -699,18 +695,13 @@ struct kern_ipc_perm ipc_lock(struct ipc_ids ids, int id)
		struct kern_ipc_perm *out;
		int lid = ipcid_to_idx(id);

		down_read(&ids->rw_mutex);

		rcu_read_lock();
		out = idr_find(&ids->ipcs_idr, lid);
		if (out == NULL) {
		rcu_read_unlock();
		up_read(&ids->rw_mutex);
		return ERR_PTR(-EINVAL);
		}

		up_read(&ids->rw_mutex);

		spin_lock(&out->lock);

		/* ipc_rmid() may have already freed the ID while ipc_lock

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