Messages in this thread | | | Date | Wed, 8 Aug 2007 01:37:49 +0400 | From | Oleg Nesterov <> | Subject | Re: [NFS] 2.6.23-rc1-mm2 |
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On 08/07, Trond Myklebust wrote: > > On Fri, 2007-08-03 at 21:21 +0400, Oleg Nesterov wrote: > > On 08/03, Trond Myklebust wrote: > > > I'll have a look at this. I suspect that most if not all of our calls to > > > run_workqueue()/flush_scheduled_work() can now be replaced by more > > > targeted calls to cancel_work_sync() and cancel_delayed_work_sync(). > > > > Yes, please, if possible. > > All the NFS and SUNRPC cases appear to be trivial. IOW: the only reason > for the flush_workqueue()/flush_scheduled_work() calls was to ensure > that the cancel_work()/cancel_delayed_work() calls preceding them have > completed. Nevertheless I've split the conversion into two patches, > since one touches only the NFS code, whereas the other touches the > SUNRPC client and server code. > > The two patches have been tested, and appear to work...
Great!
> void > nfs4_kill_renewd(struct nfs_client *clp) > { > down_read(&clp->cl_sem); > - cancel_delayed_work(&clp->cl_renewd); > + cancel_delayed_work_sync(&clp->cl_renewd); > up_read(&clp->cl_sem); > - flush_scheduled_work(); > }
this looks unsafe to me, the window is very small, but afaics this can deadlock if called when nfs4_renew_state() has already started, but didn't take ->cl_sem yet.
Can't we avoid taking clp->cl_sem here?
Btw, unless I missed something, the code without this patch looks incorrect too: cancel_delayed_work() can fail if the timer expired, but the ->cl_renewd didn't run yet. In that case nfs4_renew_state() can run and re-schedule itself after flush_scheduled_work() returns.
Oleg.
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