From 7dc5d24be06a5ed874af035d52a083a7b61ef1bd Mon Sep 17 00:00:00 2001 From: Tejun Heo Date: Wed, 24 Sep 2008 16:22:23 -0500 Subject: [PATCH] 9p-trans_fd: fix trans_fd::p9_conn_destroy() p9_conn_destroy() first kills all current requests by calling p9_conn_cancel(), then waits for the request list to be cleared by waiting on p9_conn->equeue. After that, polling is stopped and the trans is destroyed. This sequence has a few problems. * Read and write works were never cancelled and the p9_conn can be destroyed while the works are running as r/w works remove requests from the list and dereference the p9_conn from them. * The list emptiness wait using p9_conn->equeue wouldn't trigger because p9_conn_cancel() always clears all the lists and the only way the wait can be triggered is to have another task to issue a request between the slim window between p9_conn_cancel() and the wait, which isn't safe under the current implementation with or without the wait. This patch fixes the problem by first stopping poll, which can schedule r/w works, first and cancle r/w works which guarantees that r/w works are not and will not run from that point and then calling p9_conn_cancel() and do the rest of destruction. Signed-off-by: Tejun Heo Signed-off-by: Eric Van Hensbergen --- net/9p/trans_fd.c | 24 +++++------------------- 1 file changed, 5 insertions(+), 19 deletions(-) diff --git a/net/9p/trans_fd.c b/net/9p/trans_fd.c index 6a32ffdb9429..ee0d151da31a 100644 --- a/net/9p/trans_fd.c +++ b/net/9p/trans_fd.c @@ -151,7 +151,6 @@ struct p9_mux_poll_task { * @trans: reference to transport instance for this connection * @tagpool: id accounting for transactions * @err: error state - * @equeue: event wait_q (?) * @req_list: accounting for requests which have been sent * @unsent_req_list: accounting for requests that haven't been sent * @rcall: current response &p9_fcall structure @@ -178,7 +177,6 @@ struct p9_conn { struct p9_trans *trans; struct p9_idpool *tagpool; int err; - wait_queue_head_t equeue; struct list_head req_list; struct list_head unsent_req_list; struct p9_fcall *rcall; @@ -430,7 +428,6 @@ static struct p9_conn *p9_conn_create(struct p9_trans *trans) } m->err = 0; - init_waitqueue_head(&m->equeue); INIT_LIST_HEAD(&m->req_list); INIT_LIST_HEAD(&m->unsent_req_list); m->rcall = NULL; @@ -483,18 +480,13 @@ static void p9_conn_destroy(struct p9_conn *m) { P9_DPRINTK(P9_DEBUG_MUX, "mux %p prev %p next %p\n", m, m->mux_list.prev, m->mux_list.next); - p9_conn_cancel(m, -ECONNRESET); - - if (!list_empty(&m->req_list)) { - /* wait until all processes waiting on this session exit */ - P9_DPRINTK(P9_DEBUG_MUX, - "mux %p waiting for empty request queue\n", m); - wait_event_timeout(m->equeue, (list_empty(&m->req_list)), 5000); - P9_DPRINTK(P9_DEBUG_MUX, "mux %p request queue empty: %d\n", m, - list_empty(&m->req_list)); - } p9_mux_poll_stop(m); + cancel_work_sync(&m->rq); + cancel_work_sync(&m->wq); + + p9_conn_cancel(m, -ECONNRESET); + m->trans = NULL; p9_idpool_destroy(m->tagpool); kfree(m); @@ -840,8 +832,6 @@ static void p9_read_work(struct work_struct *work) (*req->cb) (req, req->cba); else kfree(req->rcall); - - wake_up(&m->equeue); } } else { if (err >= 0 && rcall->id != P9_RFLUSH) @@ -984,8 +974,6 @@ static void p9_mux_flush_cb(struct p9_req *freq, void *a) (*req->cb) (req, req->cba); else kfree(req->rcall); - - wake_up(&m->equeue); } kfree(freq->tcall); @@ -1191,8 +1179,6 @@ void p9_conn_cancel(struct p9_conn *m, int err) else kfree(req->rcall); } - - wake_up(&m->equeue); } /** -- 2.20.1