From: Nadia Derbey Call idr_find() locklessly from ipc_lock(), since the idr tree is now RCU protected. Signed-off-by: Nadia Derbey Cc: "Paul E. McKenney" Cc: Manfred Spraul Cc: Jim Houston Cc: Pierre Peiffer Signed-off-by: Andrew Morton --- ipc/util.c | 9 --------- 1 file changed, 9 deletions(-) diff -puN ipc/util.c~ipc-call-idr_find-without-locking-in-ipc_lock ipc/util.c --- a/ipc/util.c~ipc-call-idr_find-without-locking-in-ipc_lock +++ a/ipc/util.c @@ -688,10 +688,6 @@ void ipc64_perm_to_ipc_perm (struct ipc6 * 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 ip 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 _