From: Jeff Layton Subject: Re: [2.6.26-rc4] mount.nfsv4/memory poisoning issues... Date: Tue, 10 Jun 2008 16:41:47 -0400 Message-ID: <20080610164147.671e2cc3@tleilax.poochiereds.net> References: <6278d2220806041633n3bfe3dd2ke9602697697228b@mail.gmail.com> <20080604203504.62730951@tleilax.poochiereds.net> <1213124088.20459.16.camel@localhost> <20080610151357.150b6f69@tleilax.poochiereds.net> <1213127909.20459.48.camel@localhost> <20080610161352.4e588653@tleilax.poochiereds.net> <1213130012.20459.58.camel@localhost> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Cc: nfsv4@linux-nfs.org, linux-nfs@vger.kernel.org, Daniel J Blueman , Linux Kernel To: Trond Myklebust Return-path: In-Reply-To: <1213130012.20459.58.camel@localhost> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: nfsv4-bounces@linux-nfs.org Errors-To: nfsv4-bounces@linux-nfs.org List-ID: On Tue, 10 Jun 2008 16:33:32 -0400 Trond Myklebust wrote: > On Tue, 2008-06-10 at 16:13 -0400, Jeff Layton wrote: > > > We can't call nfs_callback_down() until after nfs_callback_up() > > returns, so we're guaranteed to have "task" set to a valid task > > (presuming that nfs_callback_up() doesn't return error). We also can't > > return from nfs_callback_down() until after the nfs_callback_svc() has > > exited. kthread_stop() will block until it does. > > The code I'm alluding to is in kthread(): > > /* OK, tell user we're spawned, wait for stop or wakeup */ > __set_current_state(TASK_UNINTERRUPTIBLE); > complete(&create->started); > schedule(); > > if (!kthread_should_stop()) > ret = threadfn(data); > > schedule() is called _after_ the complete() call, and _before_ we > execute threadfn() a.k.a. nfs_callback_svc(). If nfs_alloc_client() has > time to call nfs_callback_down() before the above thread gets scheduled > back in, then threadfn() doesn't get called at all, since > kthread_should_stop() is true. > That makes total sense. Thanks for clearing it up. Cheers, -- Jeff Layton