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Commit b274b48f3ef6e43e3831e8793c697a9573a607af

Authored by Trond Myklebust
1 parent e9cc6c234b
Exists in master and in 7 other branches imx_3.0.35_4.1.0, imx_3.10.17_1.0.1_ga, imx_3.10.53_1.1.0_ga, imx_3.14.28_1.0.0_ga, smarc-imx_3.10.53_1.1.0_ga, smarc-imx_3.14.28_1.0.0_ga, smarc-l5.0.0_1.0.0-ga

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>

Showing 1 changed file with 0 additions and 2 deletions Inline Diff

1 /* 1 /*
2 * fs/nfs/nfs4renewd.c 2 * fs/nfs/nfs4renewd.c
3 * 3 *
4 * Copyright (c) 2002 The Regents of the University of Michigan. 4 * Copyright (c) 2002 The Regents of the University of Michigan.
5 * All rights reserved. 5 * All rights reserved.
6 * 6 *
7 * Kendrick Smith <kmsmith@umich.edu> 7 * Kendrick Smith <kmsmith@umich.edu>
8 * 8 *
9 * Redistribution and use in source and binary forms, with or without 9 * Redistribution and use in source and binary forms, with or without
10 * modification, are permitted provided that the following conditions 10 * modification, are permitted provided that the following conditions
11 * are met: 11 * are met:
12 * 12 *
13 * 1. Redistributions of source code must retain the above copyright 13 * 1. Redistributions of source code must retain the above copyright
14 * notice, this list of conditions and the following disclaimer. 14 * notice, this list of conditions and the following disclaimer.
15 * 2. Redistributions in binary form must reproduce the above copyright 15 * 2. Redistributions in binary form must reproduce the above copyright
16 * notice, this list of conditions and the following disclaimer in the 16 * notice, this list of conditions and the following disclaimer in the
17 * documentation and/or other materials provided with the distribution. 17 * documentation and/or other materials provided with the distribution.
18 * 3. Neither the name of the University nor the names of its 18 * 3. Neither the name of the University nor the names of its
19 * contributors may be used to endorse or promote products derived 19 * contributors may be used to endorse or promote products derived
20 * from this software without specific prior written permission. 20 * from this software without specific prior written permission.
21 * 21 *
22 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED 22 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED
23 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF 23 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
24 * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE 24 * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
25 * DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 25 * DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
26 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 26 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
27 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 27 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
28 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR 28 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
29 * BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF 29 * BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
30 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING 30 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
31 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS 31 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
32 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 32 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
33 * 33 *
34 * Implementation of the NFSv4 "renew daemon", which wakes up periodically to 34 * Implementation of the NFSv4 "renew daemon", which wakes up periodically to
35 * send a RENEW, to keep state alive on the server. The daemon is implemented 35 * send a RENEW, to keep state alive on the server. The daemon is implemented
36 * as an rpc_task, not a real kernel thread, so it always runs in rpciod's 36 * as an rpc_task, not a real kernel thread, so it always runs in rpciod's
37 * context. There is one renewd per nfs_server. 37 * context. There is one renewd per nfs_server.
38 * 38 *
39 * TODO: If the send queue gets backlogged (e.g., if the server goes down), 39 * TODO: If the send queue gets backlogged (e.g., if the server goes down),
40 * we will keep filling the queue with periodic RENEW requests. We need a 40 * we will keep filling the queue with periodic RENEW requests. We need a
41 * mechanism for ensuring that if renewd successfully sends off a request, 41 * mechanism for ensuring that if renewd successfully sends off a request,
42 * then it only wakes up when the request is finished. Maybe use the 42 * then it only wakes up when the request is finished. Maybe use the
43 * child task framework of the RPC layer? 43 * child task framework of the RPC layer?
44 */ 44 */
45 45
46 #include <linux/mm.h> 46 #include <linux/mm.h>
47 #include <linux/pagemap.h> 47 #include <linux/pagemap.h>
48 #include <linux/sunrpc/sched.h> 48 #include <linux/sunrpc/sched.h>
49 #include <linux/sunrpc/clnt.h> 49 #include <linux/sunrpc/clnt.h>
50 50
51 #include <linux/nfs.h> 51 #include <linux/nfs.h>
52 #include <linux/nfs4.h> 52 #include <linux/nfs4.h>
53 #include <linux/nfs_fs.h> 53 #include <linux/nfs_fs.h>
54 #include "nfs4_fs.h" 54 #include "nfs4_fs.h"
55 #include "delegation.h" 55 #include "delegation.h"
56 56
57 #define NFSDBG_FACILITY NFSDBG_PROC 57 #define NFSDBG_FACILITY NFSDBG_PROC
58 58
59 void 59 void
60 nfs4_renew_state(struct work_struct *work) 60 nfs4_renew_state(struct work_struct *work)
61 { 61 {
62 struct nfs_client *clp = 62 struct nfs_client *clp =
63 container_of(work, struct nfs_client, cl_renewd.work); 63 container_of(work, struct nfs_client, cl_renewd.work);
64 struct rpc_cred *cred; 64 struct rpc_cred *cred;
65 long lease, timeout; 65 long lease, timeout;
66 unsigned long last, now; 66 unsigned long last, now;
67 67
68 down_read(&clp->cl_sem); 68 down_read(&clp->cl_sem);
69 dprintk("%s: start\n", __FUNCTION__); 69 dprintk("%s: start\n", __FUNCTION__);
70 /* Are there any active superblocks? */ 70 /* Are there any active superblocks? */
71 if (list_empty(&clp->cl_superblocks)) 71 if (list_empty(&clp->cl_superblocks))
72 goto out; 72 goto out;
73 spin_lock(&clp->cl_lock); 73 spin_lock(&clp->cl_lock);
74 lease = clp->cl_lease_time; 74 lease = clp->cl_lease_time;
75 last = clp->cl_last_renewal; 75 last = clp->cl_last_renewal;
76 now = jiffies; 76 now = jiffies;
77 timeout = (2 * lease) / 3 + (long)last - (long)now; 77 timeout = (2 * lease) / 3 + (long)last - (long)now;
78 /* Are we close to a lease timeout? */ 78 /* Are we close to a lease timeout? */
79 if (time_after(now, last + lease/3)) { 79 if (time_after(now, last + lease/3)) {
80 cred = nfs4_get_renew_cred(clp); 80 cred = nfs4_get_renew_cred(clp);
81 if (cred == NULL) { 81 if (cred == NULL) {
82 set_bit(NFS4CLNT_LEASE_EXPIRED, &clp->cl_state); 82 set_bit(NFS4CLNT_LEASE_EXPIRED, &clp->cl_state);
83 spin_unlock(&clp->cl_lock); 83 spin_unlock(&clp->cl_lock);
84 nfs_expire_all_delegations(clp); 84 nfs_expire_all_delegations(clp);
85 goto out; 85 goto out;
86 } 86 }
87 spin_unlock(&clp->cl_lock); 87 spin_unlock(&clp->cl_lock);
88 /* Queue an asynchronous RENEW. */ 88 /* Queue an asynchronous RENEW. */
89 nfs4_proc_async_renew(clp, cred); 89 nfs4_proc_async_renew(clp, cred);
90 put_rpccred(cred); 90 put_rpccred(cred);
91 timeout = (2 * lease) / 3; 91 timeout = (2 * lease) / 3;
92 spin_lock(&clp->cl_lock); 92 spin_lock(&clp->cl_lock);
93 } else 93 } else
94 dprintk("%s: failed to call renewd. Reason: lease not expired \n", 94 dprintk("%s: failed to call renewd. Reason: lease not expired \n",
95 __FUNCTION__); 95 __FUNCTION__);
96 if (timeout < 5 * HZ) /* safeguard */ 96 if (timeout < 5 * HZ) /* safeguard */
97 timeout = 5 * HZ; 97 timeout = 5 * HZ;
98 dprintk("%s: requeueing work. Lease period = %ld\n", 98 dprintk("%s: requeueing work. Lease period = %ld\n",
99 __FUNCTION__, (timeout + HZ - 1) / HZ); 99 __FUNCTION__, (timeout + HZ - 1) / HZ);
100 cancel_delayed_work(&clp->cl_renewd); 100 cancel_delayed_work(&clp->cl_renewd);
101 schedule_delayed_work(&clp->cl_renewd, timeout); 101 schedule_delayed_work(&clp->cl_renewd, timeout);
102 spin_unlock(&clp->cl_lock); 102 spin_unlock(&clp->cl_lock);
103 out: 103 out:
104 up_read(&clp->cl_sem); 104 up_read(&clp->cl_sem);
105 dprintk("%s: done\n", __FUNCTION__); 105 dprintk("%s: done\n", __FUNCTION__);
106 } 106 }
107 107
108 /* Must be called with clp->cl_sem locked for writes */ 108 /* Must be called with clp->cl_sem locked for writes */
109 void 109 void
110 nfs4_schedule_state_renewal(struct nfs_client *clp) 110 nfs4_schedule_state_renewal(struct nfs_client *clp)
111 { 111 {
112 long timeout; 112 long timeout;
113 113
114 spin_lock(&clp->cl_lock); 114 spin_lock(&clp->cl_lock);
115 timeout = (2 * clp->cl_lease_time) / 3 + (long)clp->cl_last_renewal 115 timeout = (2 * clp->cl_lease_time) / 3 + (long)clp->cl_last_renewal
116 - (long)jiffies; 116 - (long)jiffies;
117 if (timeout < 5 * HZ) 117 if (timeout < 5 * HZ)
118 timeout = 5 * HZ; 118 timeout = 5 * HZ;
119 dprintk("%s: requeueing work. Lease period = %ld\n", 119 dprintk("%s: requeueing work. Lease period = %ld\n",
120 __FUNCTION__, (timeout + HZ - 1) / HZ); 120 __FUNCTION__, (timeout + HZ - 1) / HZ);
121 cancel_delayed_work(&clp->cl_renewd); 121 cancel_delayed_work(&clp->cl_renewd);
122 schedule_delayed_work(&clp->cl_renewd, timeout); 122 schedule_delayed_work(&clp->cl_renewd, timeout);
123 set_bit(NFS_CS_RENEWD, &clp->cl_res_state); 123 set_bit(NFS_CS_RENEWD, &clp->cl_res_state);
124 spin_unlock(&clp->cl_lock); 124 spin_unlock(&clp->cl_lock);
125 } 125 }
126 126
127 void 127 void
128 nfs4_renewd_prepare_shutdown(struct nfs_server *server) 128 nfs4_renewd_prepare_shutdown(struct nfs_server *server)
129 { 129 {
130 cancel_delayed_work(&server->nfs_client->cl_renewd); 130 cancel_delayed_work(&server->nfs_client->cl_renewd);
131 } 131 }
132 132
133 void 133 void
134 nfs4_kill_renewd(struct nfs_client *clp) 134 nfs4_kill_renewd(struct nfs_client *clp)
135 { 135 {
136 down_read(&clp->cl_sem);
137 cancel_delayed_work_sync(&clp->cl_renewd); 136 cancel_delayed_work_sync(&clp->cl_renewd);
138 up_read(&clp->cl_sem);
139 } 137 }
140 138
141 /* 139 /*
142 * Local variables: 140 * Local variables:
143 * c-basic-offset: 8 141 * c-basic-offset: 8
144 * End: 142 * End:
145 */ 143 */
146 144