From mboxrd@z Thu Jan 1 00:00:00 1970 From: Peter Zijlstra Subject: Re: [PATCH] netdev: Fix sleeping inside wait event Date: Wed, 29 Oct 2014 18:31:10 +0100 Message-ID: <20141029173110.GE15602@worktop.programming.kicks-ass.net> References: <20141028142541.GA19097@wfg-t540p.sh.intel.com> <20141029161657.GF3337@twins.programming.kicks-ass.net> <20141029171345.GO12706@worktop.programming.kicks-ass.net> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Fengguang Wu , LKP , LKML , "oleg@redhat.com" , "Eric W. Biederman" , David Miller , Linux Kernel Network Developers To: Cong Wang Return-path: Content-Disposition: inline In-Reply-To: <20141029171345.GO12706@worktop.programming.kicks-ass.net> Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org On Wed, Oct 29, 2014 at 06:13:45PM +0100, Peter Zijlstra wrote: > On Wed, Oct 29, 2014 at 09:29:55AM -0700, Cong Wang wrote: > > While you are on it, please fix rtnl_lock_unregistering_all() too? > > Ah, that's hidden someplace else, sure I can do that. Thanks for > pointing it out. Here goes.. --- Subject: netdev: Fix sleeping inside wait event From: Peter Zijlstra Date: Wed Oct 29 17:04:56 CET 2014 rtnl_lock_unregistering*() take rtnl_lock() -- a mutex -- inside a wait loop. The wait loop relies on current->state to function, but so does mutex_lock(), nesting them makes for the inner to destroy the outer state. Fix this using the new wait_woken() bits. Cc: David Miller Cc: Oleg Nesterov Cc: Eric Biederman Reported-by: Fengguang Wu Signed-off-by: Peter Zijlstra (Intel) --- net/core/dev.c | 10 +++++----- net/core/rtnetlink.c | 10 +++++----- 2 files changed, 10 insertions(+), 10 deletions(-) --- a/net/core/dev.c +++ b/net/core/dev.c @@ -7196,11 +7196,10 @@ static void __net_exit rtnl_lock_unregis */ struct net *net; bool unregistering; - DEFINE_WAIT(wait); + DEFINE_WAIT_FUNC(wait, woken_wake_function); + add_wait_queue(&netdev_unregistering_wq, &wait); for (;;) { - prepare_to_wait(&netdev_unregistering_wq, &wait, - TASK_UNINTERRUPTIBLE); unregistering = false; rtnl_lock(); list_for_each_entry(net, net_list, exit_list) { @@ -7212,9 +7211,10 @@ static void __net_exit rtnl_lock_unregis if (!unregistering) break; __rtnl_unlock(); - schedule(); + + wait_woken(&wait, TASK_UNINTERRUPTIBLE, MAX_SCHEDULE_TIMEOUT); } - finish_wait(&netdev_unregistering_wq, &wait); + remove_wait_queue(&netdev_unregistering_wq, &wait); } static void __net_exit default_device_exit_batch(struct list_head *net_list) --- a/net/core/rtnetlink.c +++ b/net/core/rtnetlink.c @@ -365,11 +365,10 @@ static void rtnl_lock_unregistering_all( { struct net *net; bool unregistering; - DEFINE_WAIT(wait); + DEFINE_WAIT_FUNC(wait, woken_wake_function); + add_wait_queue(&netdev_unregistering_wq, &wait); for (;;) { - prepare_to_wait(&netdev_unregistering_wq, &wait, - TASK_UNINTERRUPTIBLE); unregistering = false; rtnl_lock(); for_each_net(net) { @@ -381,9 +380,10 @@ static void rtnl_lock_unregistering_all( if (!unregistering) break; __rtnl_unlock(); - schedule(); + + wait_woken(&wait, TASK_UNINTERRUPTIBLE, MAX_SCHEDULE_TIMEOUT); } - finish_wait(&netdev_unregistering_wq, &wait); + remove_wait_queue(&netdev_unregistering_wq, &wait); } /**