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SubjectRE: [PATCH 3/5] rapidio: run discovery as an asynchronous process
Date
On Wed, October 03, 2012 6:30 PM
Andrew Morton <akpm@linux-foundation.org> wrote:
>
> On Wed, 3 Oct 2012 15:18:41 -0400
> Alexandre Bounine <alexandre.bounine@idt.com> wrote:
>
> > ...
> >
> > +static void __devinit disc_work_handler(struct work_struct *_work)
> > +{
> > + struct rio_disc_work *work = container_of(_work,
> > + struct rio_disc_work, work);
>
> There's a nice simple way to avoid such ugliness:
>
> --- a/drivers/rapidio/rio.c~rapidio-run-discovery-as-an-asynchronous-
> process-fix
> +++ a/drivers/rapidio/rio.c
> @@ -1269,9 +1269,9 @@ struct rio_disc_work {
>
> static void __devinit disc_work_handler(struct work_struct *_work)
> {
> - struct rio_disc_work *work = container_of(_work,
> - struct rio_disc_work, work);
> + struct rio_disc_work *work;
>
> + work = container_of(_work, struct rio_disc_work, work);
> pr_debug("RIO: discovery work for mport %d %s\n",
> work->mport->id, work->mport->name);
> rio_disc_mport(work->mport);
> _
>

Thank you for the fix. Will avoid that ugliness in the future.

> > + pr_debug("RIO: discovery work for mport %d %s\n",
> > + work->mport->id, work->mport->name);
> > + rio_disc_mport(work->mport);
> > +
> > + kfree(work);
> > +}
> > +
> > int __devinit rio_init_mports(void)
> > {
> > struct rio_mport *port;
> > + struct rio_disc_work *work;
> > + int no_disc = 0;
> >
> > list_for_each_entry(port, &rio_mports, node) {
> > if (port->host_deviceid >= 0)
> > rio_enum_mport(port);
> > - else
> > - rio_disc_mport(port);
> > + else if (!no_disc) {
> > + if (!rio_wq) {
> > + rio_wq = alloc_workqueue("riodisc", 0, 0);
> > + if (!rio_wq) {
> > + pr_err("RIO: unable allocate rio_wq\n");
> > + no_disc = 1;
> > + continue;
> > + }
> > + }
> > +
> > + work = kzalloc(sizeof *work, GFP_KERNEL);
> > + if (!work) {
> > + pr_err("RIO: no memory for work struct\n");
> > + no_disc = 1;
> > + continue;
> > + }
> > +
> > + work->mport = port;
> > + INIT_WORK(&work->work, disc_work_handler);
> > + queue_work(rio_wq, &work->work);
> > + }
> > + }
>
> I'm having a lot of trouble with `no_disc'. afacit what it does is to
> cease running async discovery for any remaining devices if the
> workqueue
> allocation failed (vaguely reasonable) or if the allocation of a single
> work item failed (incomprehensible).
>
> But if we don't run discovery, the subsystem is permanently busted for
> at least some devices, isn't it?

This is correct. We are considering ways to restart discovery
process later but it is not applicable now.

>
> And this code is basically untestable unless the programmer does
> deliberate fault injection, which makes it pretty much unmaintainable.
>
> So... if I haven't totally misunderstood, I suggest a rethink is in
> order?
>

I will review and simplify. Probably, just try to allocate all required
resources ahead of port list scan. Simple and safe.

> > + if (rio_wq) {
> > + pr_debug("RIO: flush discovery workqueue\n");
> > + flush_workqueue(rio_wq);
> > + pr_debug("RIO: flush discovery workqueue finished\n");
> > + destroy_workqueue(rio_wq);
> > }


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