From 150a6b478982475c60fa25b7060ab990ece5483d Mon Sep 17 00:00:00 2001 From: Nathaniel Wesley Filardo Date: Wed, 21 May 2014 14:58:26 +0100 Subject: [PATCH] AFS: Fix kafs module unloading At present, it is not possible to successfully unload the kafs module if there are outstanding async outgoing calls (those made with afs_make_call()). This appears to be due to the changes introduced by: commit 059499453a9abd1857d442b44da8b4c126dc72a8 Author: Tejun Heo Date: Fri Mar 7 10:24:50 2014 -0500 Subject: afs: don't use PREPARE_WORK which didn't go far enough. The problem is due to: (1) The aforementioned commit introduced a separate handler function pointer in the call, call->async_workfn, in addition to the original workqueue item, call->async_work, for asynchronous operations because workqueues subsystem cannot handle the workqueue item pointer being changed whilst the item is queued or being processed. (2) afs_async_workfn() was introduced in that commit to be the callback for call->async_work. Its sole purpose is to run whatever call->async_workfn points to. (3) call->async_workfn is only used from afs_async_workfn(), which is only set on async_work by afs_collect_incoming_call() - ie. for incoming calls. (4) call->async_workfn is *not* set by afs_make_call() when outgoing calls are made, and call->async_work is set afs_process_async_call() - and not afs_async_workfn(). (5) afs_process_async_call() now changes call->async_workfn rather than call->async_work to point to afs_delete_async_call() to clean up, but this is only effective for incoming calls because call->async_work does not point to afs_async_workfn() for outgoing calls. (6) Because, for incoming calls, call->async_work remains pointing to afs_process_async_call() this results in an infinite loop. Instead, make the workqueue uniformly vector through call->async_workfn, via afs_async_workfn() and simply initialise call->async_workfn to point to afs_process_async_call() in afs_make_call(). Signed-off-by: Nathaniel Wesley Filardo Signed-off-by: David Howells Reviewed-by: Tejun Heo --- fs/afs/rxrpc.c | 17 +++++++++-------- 1 file changed, 9 insertions(+), 8 deletions(-) diff --git a/fs/afs/rxrpc.c b/fs/afs/rxrpc.c index 1a1110b..5a05014 100644 --- a/fs/afs/rxrpc.c +++ b/fs/afs/rxrpc.c @@ -58,6 +58,13 @@ static void afs_collect_incoming_call(struct work_struct *); static struct sk_buff_head afs_incoming_calls; static DECLARE_WORK(afs_collect_incoming_call_work, afs_collect_incoming_call); +static void afs_async_workfn(struct work_struct *work) +{ + struct afs_call *call = container_of(work, struct afs_call, async_work); + + call->async_workfn(work); +} + /* * open an RxRPC socket and bind it to be a server for callback notifications * - the socket is left in blocking mode and non-blocking ops use MSG_DONTWAIT @@ -348,7 +355,8 @@ int afs_make_call(struct in_addr *addr, struct afs_call *call, gfp_t gfp, atomic_read(&afs_outstanding_calls)); call->wait_mode = wait_mode; - INIT_WORK(&call->async_work, afs_process_async_call); + call->async_workfn = afs_process_async_call; + INIT_WORK(&call->async_work, afs_async_workfn); memset(&srx, 0, sizeof(srx)); srx.srx_family = AF_RXRPC; @@ -672,13 +680,6 @@ void afs_transfer_reply(struct afs_call *call, struct sk_buff *skb) call->reply_size += len; } -static void afs_async_workfn(struct work_struct *work) -{ - struct afs_call *call = container_of(work, struct afs_call, async_work); - - call->async_workfn(work); -} - /* * accept the backlog of incoming calls */ -- 2.7.4