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Date: Fri, 30 May 2008 01:29:04 -0700
From: "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To: Nadia.Derbey@...l.net
Cc: manfred@...orfullife.com, lnxninja@...ux.vnet.ibm.com,
linux-kernel@...r.kernel.org, efault@....de,
akpm@...ux-foundation.org
Subject: Re: [PATCH 9/9] Get rid of ipc_lock_down()
On Wed, May 07, 2008 at 01:36:02PM +0200, Nadia.Derbey@...l.net wrote:
> [PATCH 09/09]
>
> This patch removes the ipc_lock_down() routines: they used to call idr_find()
> locklessly (given that the ipc ids lock was already held), so they are not
> needed anymore.
Acked-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
> Signed-off-by: Nadia Derbey <Nadia.Derbey@...l.net>
>
> ---
> ipc/shm.c | 21 +++------------------
> ipc/util.c | 52 +---------------------------------------------------
> ipc/util.h | 6 ------
> 3 files changed, 4 insertions(+), 75 deletions(-)
>
> Index: linux-2.6.25-mm1/ipc/util.c
> ===================================================================
> --- linux-2.6.25-mm1.orig/ipc/util.c 2008-05-07 09:56:20.000000000 +0200
> +++ linux-2.6.25-mm1/ipc/util.c 2008-05-07 09:58:32.000000000 +0200
> @@ -716,56 +716,6 @@ struct kern_ipc_perm *ipc_lock(struct ip
> return out;
> }
>
> -/**
> - * ipc_lock_down - Lock an ipc structure with rw_sem held
> - * @ids: IPC identifier set
> - * @id: ipc id to look for
> - *
> - * 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 already
> - * held, i.e. idr tree protected.
> - */
> -
> -struct kern_ipc_perm *ipc_lock_down(struct ipc_ids *ids, int id)
> -{
> - struct kern_ipc_perm *out;
> - int lid = ipcid_to_idx(id);
> -
> - rcu_read_lock();
> - out = idr_find(&ids->ipcs_idr, lid);
> - if (out == NULL) {
> - rcu_read_unlock();
> - return ERR_PTR(-EINVAL);
> - }
> -
> - spin_lock(&out->lock);
> -
> - /*
> - * No need to verify that the structure is still valid since the
> - * rw_mutex is held.
> - */
> - return out;
> -}
> -
> -struct kern_ipc_perm *ipc_lock_check_down(struct ipc_ids *ids, int id)
> -{
> - struct kern_ipc_perm *out;
> -
> - out = ipc_lock_down(ids, id);
> - if (IS_ERR(out))
> - return out;
> -
> - if (ipc_checkid(out, id)) {
> - ipc_unlock(out);
> - return ERR_PTR(-EIDRM);
> - }
> -
> - return out;
> -}
> -
> struct kern_ipc_perm *ipc_lock_check(struct ipc_ids *ids, int id)
> {
> struct kern_ipc_perm *out;
> @@ -837,7 +787,7 @@ struct kern_ipc_perm *ipcctl_pre_down(st
> int err;
>
> down_write(&ids->rw_mutex);
> - ipcp = ipc_lock_check_down(ids, id);
> + ipcp = ipc_lock_check(ids, id);
> if (IS_ERR(ipcp)) {
> err = PTR_ERR(ipcp);
> goto out_up;
> Index: linux-2.6.25-mm1/ipc/util.h
> ===================================================================
> --- linux-2.6.25-mm1.orig/ipc/util.h 2008-05-06 17:15:10.000000000 +0200
> +++ linux-2.6.25-mm1/ipc/util.h 2008-05-07 09:59:31.000000000 +0200
> @@ -102,11 +102,6 @@ void* ipc_rcu_alloc(int size);
> void ipc_rcu_getref(void *ptr);
> void ipc_rcu_putref(void *ptr);
>
> -/*
> - * ipc_lock_down: called with rw_mutex held
> - * ipc_lock: called without that lock held
> - */
> -struct kern_ipc_perm *ipc_lock_down(struct ipc_ids *, int);
> struct kern_ipc_perm *ipc_lock(struct ipc_ids *, int);
>
> void kernel_to_ipc64_perm(struct kern_ipc_perm *in, struct ipc64_perm *out);
> @@ -155,7 +150,6 @@ static inline void ipc_unlock(struct ker
> rcu_read_unlock();
> }
>
> -struct kern_ipc_perm *ipc_lock_check_down(struct ipc_ids *ids, int id);
> struct kern_ipc_perm *ipc_lock_check(struct ipc_ids *ids, int id);
> int ipcget(struct ipc_namespace *ns, struct ipc_ids *ids,
> struct ipc_ops *ops, struct ipc_params *params);
> Index: linux-2.6.25-mm1/ipc/shm.c
> ===================================================================
> --- linux-2.6.25-mm1.orig/ipc/shm.c 2008-05-06 17:15:10.000000000 +0200
> +++ linux-2.6.25-mm1/ipc/shm.c 2008-05-07 10:01:05.000000000 +0200
> @@ -112,23 +112,8 @@ void __init shm_init (void)
> }
>
> /*
> - * shm_lock_(check_)down routines are called in the paths where the rw_mutex
> - * is held to protect access to the idr tree.
> - */
> -static inline struct shmid_kernel *shm_lock_down(struct ipc_namespace *ns,
> - int id)
> -{
> - struct kern_ipc_perm *ipcp = ipc_lock_down(&shm_ids(ns), id);
> -
> - if (IS_ERR(ipcp))
> - return (struct shmid_kernel *)ipcp;
> -
> - return container_of(ipcp, struct shmid_kernel, shm_perm);
> -}
> -
> -/*
> * shm_lock_(check_) routines are called in the paths where the rw_mutex
> - * is not held.
> + * is not necessarily held.
> */
> static inline struct shmid_kernel *shm_lock(struct ipc_namespace *ns, int id)
> {
> @@ -211,7 +196,7 @@ static void shm_close(struct vm_area_str
>
> down_write(&shm_ids(ns).rw_mutex);
> /* remove from the list of attaches of the shm segment */
> - shp = shm_lock_down(ns, sfd->id);
> + shp = shm_lock(ns, sfd->id);
> BUG_ON(IS_ERR(shp));
> shp->shm_lprid = task_tgid_vnr(current);
> shp->shm_dtim = get_seconds();
> @@ -933,7 +918,7 @@ invalid:
>
> out_nattch:
> down_write(&shm_ids(ns).rw_mutex);
> - shp = shm_lock_down(ns, shmid);
> + shp = shm_lock(ns, shmid);
> BUG_ON(IS_ERR(shp));
> shp->shm_nattch--;
> if(shp->shm_nattch == 0 &&
>
> --
--
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