android_kernel_motorola_sm6225/fs/nfs/nfs4renewd.c
Trond Myklebust b274b48f3e NFSv4: Fix circular locking dependency in nfs4_kill_renewd
Erez Zadok reports:

=======================================================
[ INFO: possible circular locking dependency detected ]
2.6.24-rc6-unionfs2 #80
-------------------------------------------------------
umount.nfs4/4017 is trying to acquire lock:
 (&(&clp->cl_renewd)->work){--..}, at: [<c0223e53>]
__cancel_work_timer+0x83/0x17f

but task is already holding lock:
 (&clp->cl_sem){----}, at: [<f8879897>] nfs4_kill_renewd+0x17/0x29 [nfs]

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #1 (&clp->cl_sem){----}:
       [<c0230699>] __lock_acquire+0x9cc/0xb95
       [<c0230c39>] lock_acquire+0x5f/0x78
       [<c0397cb8>] down_read+0x3a/0x4c
       [<f88798e6>] nfs4_renew_state+0x1c/0x1b8 [nfs]
       [<c0223821>] run_workqueue+0xd9/0x1ac
       [<c0224220>] worker_thread+0x7a/0x86
       [<c0226b49>] kthread+0x3b/0x62
       [<c02033a3>] kernel_thread_helper+0x7/0x10
       [<ffffffff>] 0xffffffff

-> #0 (&(&clp->cl_renewd)->work){--..}:
       [<c0230589>] __lock_acquire+0x8bc/0xb95
       [<c0230c39>] lock_acquire+0x5f/0x78
       [<c0223e87>] __cancel_work_timer+0xb7/0x17f
       [<c0223f5a>] cancel_delayed_work_sync+0xb/0xd
       [<f887989e>] nfs4_kill_renewd+0x1e/0x29 [nfs]
       [<f885a8f6>] nfs_free_client+0x37/0x9e [nfs]
       [<f885ab20>] nfs_put_client+0x5d/0x62 [nfs]
       [<f885ab9a>] nfs_free_server+0x75/0xae [nfs]
       [<f8862672>] nfs4_kill_super+0x27/0x2b [nfs]
       [<c0258aab>] deactivate_super+0x3f/0x51
       [<c0269668>] mntput_no_expire+0x42/0x67
       [<c025d0e4>] path_release_on_umount+0x15/0x18
       [<c0269d30>] sys_umount+0x1a3/0x1cb
       [<c0269d71>] sys_oldumount+0x19/0x1b
       [<c02026ca>] sysenter_past_esp+0x5f/0xa5
       [<ffffffff>] 0xffffffff

Looking at the code, it would seem that taking the clp->cl_sem in
nfs4_kill_renewd is completely redundant, since we're already guaranteed to
have exclusive access to the nfs_client (we're shutting down).

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
2008-01-03 09:37:16 -05:00

143 lines
4.7 KiB
C

/*
* fs/nfs/nfs4renewd.c
*
* Copyright (c) 2002 The Regents of the University of Michigan.
* All rights reserved.
*
* Kendrick Smith <kmsmith@umich.edu>
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. Neither the name of the University nor the names of its
* contributors may be used to endorse or promote products derived
* from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED
* WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
* DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
* BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
* LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
* NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
* Implementation of the NFSv4 "renew daemon", which wakes up periodically to
* send a RENEW, to keep state alive on the server. The daemon is implemented
* as an rpc_task, not a real kernel thread, so it always runs in rpciod's
* context. There is one renewd per nfs_server.
*
* TODO: If the send queue gets backlogged (e.g., if the server goes down),
* we will keep filling the queue with periodic RENEW requests. We need a
* mechanism for ensuring that if renewd successfully sends off a request,
* then it only wakes up when the request is finished. Maybe use the
* child task framework of the RPC layer?
*/
#include <linux/mm.h>
#include <linux/pagemap.h>
#include <linux/sunrpc/sched.h>
#include <linux/sunrpc/clnt.h>
#include <linux/nfs.h>
#include <linux/nfs4.h>
#include <linux/nfs_fs.h>
#include "nfs4_fs.h"
#include "delegation.h"
#define NFSDBG_FACILITY NFSDBG_PROC
void
nfs4_renew_state(struct work_struct *work)
{
struct nfs_client *clp =
container_of(work, struct nfs_client, cl_renewd.work);
struct rpc_cred *cred;
long lease, timeout;
unsigned long last, now;
down_read(&clp->cl_sem);
dprintk("%s: start\n", __FUNCTION__);
/* Are there any active superblocks? */
if (list_empty(&clp->cl_superblocks))
goto out;
spin_lock(&clp->cl_lock);
lease = clp->cl_lease_time;
last = clp->cl_last_renewal;
now = jiffies;
timeout = (2 * lease) / 3 + (long)last - (long)now;
/* Are we close to a lease timeout? */
if (time_after(now, last + lease/3)) {
cred = nfs4_get_renew_cred(clp);
if (cred == NULL) {
set_bit(NFS4CLNT_LEASE_EXPIRED, &clp->cl_state);
spin_unlock(&clp->cl_lock);
nfs_expire_all_delegations(clp);
goto out;
}
spin_unlock(&clp->cl_lock);
/* Queue an asynchronous RENEW. */
nfs4_proc_async_renew(clp, cred);
put_rpccred(cred);
timeout = (2 * lease) / 3;
spin_lock(&clp->cl_lock);
} else
dprintk("%s: failed to call renewd. Reason: lease not expired \n",
__FUNCTION__);
if (timeout < 5 * HZ) /* safeguard */
timeout = 5 * HZ;
dprintk("%s: requeueing work. Lease period = %ld\n",
__FUNCTION__, (timeout + HZ - 1) / HZ);
cancel_delayed_work(&clp->cl_renewd);
schedule_delayed_work(&clp->cl_renewd, timeout);
spin_unlock(&clp->cl_lock);
out:
up_read(&clp->cl_sem);
dprintk("%s: done\n", __FUNCTION__);
}
/* Must be called with clp->cl_sem locked for writes */
void
nfs4_schedule_state_renewal(struct nfs_client *clp)
{
long timeout;
spin_lock(&clp->cl_lock);
timeout = (2 * clp->cl_lease_time) / 3 + (long)clp->cl_last_renewal
- (long)jiffies;
if (timeout < 5 * HZ)
timeout = 5 * HZ;
dprintk("%s: requeueing work. Lease period = %ld\n",
__FUNCTION__, (timeout + HZ - 1) / HZ);
cancel_delayed_work(&clp->cl_renewd);
schedule_delayed_work(&clp->cl_renewd, timeout);
set_bit(NFS_CS_RENEWD, &clp->cl_res_state);
spin_unlock(&clp->cl_lock);
}
void
nfs4_renewd_prepare_shutdown(struct nfs_server *server)
{
cancel_delayed_work(&server->nfs_client->cl_renewd);
}
void
nfs4_kill_renewd(struct nfs_client *clp)
{
cancel_delayed_work_sync(&clp->cl_renewd);
}
/*
* Local variables:
* c-basic-offset: 8
* End:
*/