SUNRPC: Ensure that we free the rpc_task after cleanups are done
This patch ensures that we free the rpc_task after the cleanup callbacks are done in order to avoid a deadlock problem that can be triggered if the callback needs to wait for another workqueue item to complete. Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com> Cc: Weston Andros Adamson <dros@netapp.com> Cc: Tejun Heo <tj@kernel.org> Cc: Bruce Fields <bfields@fieldses.org> Cc: stable@vger.kernel.org
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@ -934,16 +934,35 @@ struct rpc_task *rpc_new_task(const struct rpc_task_setup *setup_data)
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return task;
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}
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/*
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* rpc_free_task - release rpc task and perform cleanups
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*
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* Note that we free up the rpc_task _after_ rpc_release_calldata()
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* in order to work around a workqueue dependency issue.
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*
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* Tejun Heo states:
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* "Workqueue currently considers two work items to be the same if they're
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* on the same address and won't execute them concurrently - ie. it
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* makes a work item which is queued again while being executed wait
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* for the previous execution to complete.
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*
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* If a work function frees the work item, and then waits for an event
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* which should be performed by another work item and *that* work item
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* recycles the freed work item, it can create a false dependency loop.
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* There really is no reliable way to detect this short of verifying
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* every memory free."
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*
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*/
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static void rpc_free_task(struct rpc_task *task)
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{
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const struct rpc_call_ops *tk_ops = task->tk_ops;
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void *calldata = task->tk_calldata;
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unsigned short tk_flags = task->tk_flags;
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if (task->tk_flags & RPC_TASK_DYNAMIC) {
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rpc_release_calldata(task->tk_ops, task->tk_calldata);
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if (tk_flags & RPC_TASK_DYNAMIC) {
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dprintk("RPC: %5u freeing task\n", task->tk_pid);
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mempool_free(task, rpc_task_mempool);
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}
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rpc_release_calldata(tk_ops, calldata);
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}
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static void rpc_async_release(struct work_struct *work)
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