Hi,
BUG: atomic_dec_and_test(): -1: atomic counter underflow at:
Pid: 2827, comm: mount.nfs Not tainted 2.6.38 #1
Call Trace:
[<ffffffffa02223a0>] ? put_rpccred+0x44/0x14e [sunrpc]
[<ffffffffa021bbe9>] ? rpc_ping+0x4e/0x58 [sunrpc]
[<ffffffffa021c4a5>] ? rpc_create+0x481/0x4fc [sunrpc]
[<ffffffffa022298a>] ? rpcauth_lookup_credcache+0xab/0x22d [sunrpc]
[<ffffffffa028be8c>] ? nfs_create_rpc_client+0xa6/0xeb [nfs]
[<ffffffffa028c660>] ? nfs4_set_client+0xc2/0x1f9 [nfs]
[<ffffffffa028cd3c>] ? nfs4_create_server+0xf2/0x2a6 [nfs]
[<ffffffffa0295d07>] ? nfs4_remote_mount+0x4e/0x14a [nfs]
[<ffffffff810dd570>] ? vfs_kern_mount+0x6e/0x133
[<ffffffffa029605a>] ? nfs_do_root_mount+0x76/0x95 [nfs]
[<ffffffffa029643d>] ? nfs4_try_mount+0x56/0xaf [nfs]
[<ffffffffa0297434>] ? nfs_get_sb+0x435/0x73c [nfs]
[<ffffffff810dd59b>] ? vfs_kern_mount+0x99/0x133
[<ffffffff810dd693>] ? do_kern_mount+0x48/0xd8
[<ffffffff810f5b75>] ? do_mount+0x6da/0x741
[<ffffffff810f5c5f>] ? sys_mount+0x83/0xc0
[<ffffffff8100293b>] ? system_call_fastpath+0x16/0x1b
This is not oops, and debug code is not in vanilla. This debug code is
simple - detects atomic_dec_and_test() underflow.
Well, so, I think this is real bug of nfs codes somewhere. With some
review, the code
rpc_call_sync()
rpc_run_task
rpc_execute()
__rpc_execute()
rpc_release_task()
rpc_release_resources_task()
put_rpccred() <= release cred
rpc_put_task
rpc_do_put_task()
rpc_release_resources_task()
put_rpccred() <= release cred again
seems to be release cred unintendedly.
static void rpc_release_resources_task(struct rpc_task *task)
{
if (task->tk_rqstp)
xprt_release(task);
if (task->tk_msg.rpc_cred) {
put_rpccred(task->tk_msg.rpc_cred);
task->tk_msg.rpc_cred = NULL;
}
rpc_task_release_client(task);
}
The above change may fix the problem though, I don't know the codes what
want to do actually. And I guess this is not right fix, because the path
is looks strange - on early stage, __rpc_execute() calls
rpc_release_task() explicitly.
Thanks.
--
OGAWA Hirofumi <hirofumi@xxxxxxxxxxxxxxxxxx>
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