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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> |
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| .. | ||
| auth.h | ||
| auth_gss.h | ||
| bc_xprt.h | ||
| cache.h | ||
| clnt.h | ||
| debug.h | ||
| gss_api.h | ||
| gss_asn1.h | ||
| gss_err.h | ||
| gss_krb5.h | ||
| Kbuild | ||
| metrics.h | ||
| msg_prot.h | ||
| rpc_pipe_fs.h | ||
| rpc_rdma.h | ||
| sched.h | ||
| stats.h | ||
| svc.h | ||
| svc_rdma.h | ||
| svc_xprt.h | ||
| svcauth.h | ||
| svcauth_gss.h | ||
| svcsock.h | ||
| timer.h | ||
| types.h | ||
| xdr.h | ||
| xprt.h | ||
| xprtrdma.h | ||
| xprtsock.h | ||