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Commit c6567ed1 authored by Trond Myklebust's avatar Trond Myklebust
Browse files

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: default avatarTrond 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
parent e25fbe38

net/sunrpc/sched.c

+23 −4
Original line number Diff line number Diff line
@@ -934,16 +934,35 @@ struct rpc_task *rpc_new_task(const struct rpc_task_setup *setup_data) 
	return task;

}



/*

 * rpc_free_task - release rpc task and perform cleanups

 *

 * Note that we free up the rpc_task _after_ rpc_release_calldata()

 * in order to work around a workqueue dependency issue.

 *

 * Tejun Heo states:

 * "Workqueue currently considers two work items to be the same if they're

 * on the same address and won't execute them concurrently - ie. it

 * makes a work item which is queued again while being executed wait

 * for the previous execution to complete.

 *

 * If a work function frees the work item, and then waits for an event

 * which should be performed by another work item and *that* work item

 * recycles the freed work item, it can create a false dependency loop.

 * There really is no reliable way to detect this short of verifying

 * every memory free."

 *

 */

static void rpc_free_task(struct rpc_task *task)

{

	const struct rpc_call_ops *tk_ops = task->tk_ops;

	void *calldata = task->tk_calldata;

	unsigned short tk_flags = task->tk_flags;



	rpc_release_calldata(task->tk_ops, task->tk_calldata);



	if (task->tk_flags & RPC_TASK_DYNAMIC) {

	if (tk_flags & RPC_TASK_DYNAMIC) {

		dprintk("RPC: %5u freeing task\n", task->tk_pid);

		mempool_free(task, rpc_task_mempool);

	}

	rpc_release_calldata(tk_ops, calldata);

}



static void rpc_async_release(struct work_struct *work)