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Trond Myklebust bf294b41ce SUNRPC: Close a race in __rpc_wait_for_completion_task() ... Although they run as rpciod background tasks, under normal operation (i.e. no SIGKILL), functions like nfs_sillyrename(), nfs4_proc_unlck() and nfs4_do_close() want to be fully synchronous. This means that when we exit, we want all references to the rpc_task to be gone, and we want any dentry references etc. held by that task to be released. For this reason these functions call __rpc_wait_for_completion_task(), followed by rpc_put_task() in the expectation that the latter will be releasing the last reference to the rpc_task, and thus ensuring that the callback_ops->rpc_release() has been called synchronously. This patch fixes a race which exists due to the fact that rpciod calls rpc_complete_task() (in order to wake up the callers of __rpc_wait_for_completion_task()) and then subsequently calls rpc_put_task() without ensuring that these two steps are done atomically. In order to avoid adding new spin locks, the patch uses the existing waitqueue spin lock to order the rpc_task reference count releases between the waiting process and rpciod. The common case where nobody is waiting for completion is optimised for by checking if the RPC_TASK_ASYNC flag is cleared and/or if the rpc_task reference count is 1: in those cases we drop trying to grab the spin lock, and immediately free up the rpc_task. Those few processes that need to put the rpc_task from inside an asynchronous context and that do not care about ordering are given a new helper: rpc_put_task_async(). Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>		14 years ago
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Kbuild	…
auth.h	…
auth_gss.h	…
bc_xprt.h	NFS do not find client in NFSv4 pg_authenticate	14 years ago
cache.h	Merge branch 'for-2.6.38' of git://linux-nfs.org/~bfields/linux	14 years ago
clnt.h	…
debug.h	…
gss_api.h	…
gss_asn1.h	…
gss_err.h	…
gss_krb5.h	…
metrics.h	…
msg_prot.h	…
rpc_pipe_fs.h	…
rpc_rdma.h	…
sched.h	SUNRPC: Close a race in __rpc_wait_for_completion_task()	14 years ago
stats.h	…
svc.h	Merge branch 'for-2.6.38' of git://linux-nfs.org/~bfields/linux	14 years ago
svc_rdma.h	…
svc_xprt.h	NFS do not find client in NFSv4 pg_authenticate	14 years ago
svcauth.h	…
svcauth_gss.h	…
svcsock.h	rpc: move sk_bc_xprt to svc_xprt	14 years ago
timer.h	…
types.h	…
xdr.h	Merge branch 'bugfixes' into nfs-for-2.6.38	14 years ago
xprt.h	rpc: allow xprt_class->setup to return a preexisting xprt	14 years ago
xprtrdma.h	…
xprtsock.h	…