From mboxrd@z Thu Jan 1 00:00:00 1970 From: Trond Myklebust Subject: Re: [PATCH] RPC: killing RPC tasks races fixed Date: Thu, 17 Mar 2011 09:01:44 -0400 Message-ID: <1300366904.9654.13.camel@lade.trondhjem.org> References: <20110317121638.15035.39410.stgit@localhost6.localdomain6> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8BIT Cc: linux-nfs-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, xemul-bzQdu9zFT3WakBO8gow8eQ@public.gmane.org, neilb-l3A5Bk7waGM@public.gmane.org, netdev-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, bfields-uC3wQj2KruNg9hUCZPvPmw@public.gmane.org, davem-fT/PcQaiUtIeIZ0/mPfg9Q@public.gmane.org, skinsbursky-GEFAQzZX7r8dnm+yROfE0A@public.gmane.org To: Stanislav Kinsbursky Return-path: In-Reply-To: <20110317121638.15035.39410.stgit-bi+AKbBUZKagILUCTcTcHdKyNwTtLsGr@public.gmane.org> Sender: linux-nfs-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: netdev.vger.kernel.org On Thu, 2011-03-17 at 15:16 +0300, Stanislav Kinsbursky wrote: > task->tk_waitqueue must be checked for NULL before trying to wake up task in > rpc_killall_tasks() because it can be NULL. > > Here is an example: > > CPU 0 CPU 1 CPU 2 > -------------------- --------------------- -------------------------- > nfs4_run_open_task > rpc_run_task > rpc_execute > rpc_set_active > rpc_make_runnable > (waiting) > rpc_async_schedule > nfs4_open_prepare > nfs_wait_on_sequence > nfs_umount_begin > rpc_killall_tasks > rpc_wake_up_task > rpc_wake_up_queued_task > spin_lock(tk_waitqueue == NULL) > BUG() > rpc_sleep_on > spin_lock(&q->lock) > __rpc_sleep_on > task->tk_waitqueue = q > > Signed-off-by: Stanislav Kinsbursky > > --- > net/sunrpc/clnt.c | 4 +++- > 1 files changed, 3 insertions(+), 1 deletions(-) > > diff --git a/net/sunrpc/clnt.c b/net/sunrpc/clnt.c > index 57d344c..24039fe 100644 > --- a/net/sunrpc/clnt.c > +++ b/net/sunrpc/clnt.c > @@ -436,7 +436,9 @@ void rpc_killall_tasks(struct rpc_clnt *clnt) > if (!(rovr->tk_flags & RPC_TASK_KILLED)) { > rovr->tk_flags |= RPC_TASK_KILLED; > rpc_exit(rovr, -EIO); > - rpc_wake_up_queued_task(rovr->tk_waitqueue, rovr); > + if (rovr->tk_waitqueue) > + rpc_wake_up_queued_task(rovr->tk_waitqueue, > + rovr); Testing for RPC_IS_QUEUED(rovr) would be better, since that would optimise away the call to rpc_wake_up_queued_task() altogether for those tasks that aren't queued. > } > } > spin_unlock(&clnt->cl_lock); > -- Trond Myklebust Linux NFS client maintainer NetApp Trond.Myklebust-HgOvQuBEEgTQT0dZR+AlfA@public.gmane.org www.netapp.com -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html