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Date: Tue, 1 May 2007 03:53:23 +0300
From: Samuel Ortiz <samuel@...tiz.org>
To: Guennadi Liakhovetski <gl@...-ac.de>
Cc: irda-users@...ts.sourceforge.net,
Paul Mackerras <paulus@...ba.org>,
linux-rt-users@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [irda-users] [BUG] 2.6.20.1-rt8 irnet + pppd recursive spinlock...
On Mon, Apr 30, 2007 at 03:24:05PM +0200, Guennadi Liakhovetski wrote:
> On Tue, 10 Apr 2007, Samuel Ortiz wrote:
>
> > Hi Guennadi,
> >
> > The patch below schedules irnet_flow_indication() asynchronously. Could
> > you please give it a try (it builds, but I couldn't test it...) ? :
>
> Ok, your patch (still below) works too (now that I fixed that state
> machine race, btw, we still have to decide on the final form how it goes
> in the mainline) __after__ you also add the line
>
> + INIT_WORK(&new->irnet_flow_work, irttp_flow_restart);
>
> in irttp_dup() (remember spinlock_init()?:-)), otherwise it oopses.
good catch, again...Yes, I do remember the irttp_dup bug ;-)
> Generally, I like your patch better than mine to ppp_generic.c, where I
> explicitly check if a recursion is occurring. Still, I am a bit concerned
> about introducing yet another execution context into irda... We have seen
> a couple of locking issues there already in the last 2-3 months especially
> under rt-preempt... Would you be able to run some tests too?
I think I can run some tests here as well, but probably not as many as you:
I'm not doing IrDA stuff full time while it seems you currently are.
But I will definitely spend some time this week running my IrDA stack with this
patch applied. I didn't bother to do that earlier as you first reported some
oops with this patch applied.
> I will be
> testing it too, but don't know how much longer and how intensively. Do you
> think we might get some new problems with this new context?
It seems quite safe to me. But more importantly, I thing we do want to call
the flow indication routine asynchronously in that specific case.
There is one thing that this patch is missing though: we should probably
clean the worqueue right before we destroy the TTP instance. The work routine
checks for NULL pointer, but still...
Cheers,
Samuel.
> Thanks
> Guennadi
>
> >
> > diff --git a/include/net/irda/irttp.h b/include/net/irda/irttp.h
> > index a899e58..941f0f1 100644
> > --- a/include/net/irda/irttp.h
> > +++ b/include/net/irda/irttp.h
> > @@ -128,6 +128,7 @@ struct tsap_cb {
> >
> > struct net_device_stats stats;
> > struct timer_list todo_timer;
> > + struct work_struct irnet_flow_work; /* irttp asynchronous flow restart */
> >
> > __u32 max_seg_size; /* Max data that fit into an IrLAP frame */
> > __u8 max_header_size;
> > diff --git a/net/irda/irnet/irnet.h b/net/irda/irnet/irnet.h
> > diff --git a/net/irda/irttp.c b/net/irda/irttp.c
> > index 7069e4a..a0d0f26 100644
> > --- a/net/irda/irttp.c
> > +++ b/net/irda/irttp.c
> > @@ -367,6 +367,29 @@ static int irttp_param_max_sdu_size(void *instance, irda_param_t *param,
> > /*************************** CLIENT CALLS ***************************/
> > /************************** LMP CALLBACKS **************************/
> > /* Everything is happily mixed up. Waiting for next clean up - Jean II */
> > +static void irttp_flow_restart(struct work_struct *work)
> > +{
> > + struct tsap_cb * self =
> > + container_of(work, struct tsap_cb, irnet_flow_work);
> > +
> > + if (self == NULL)
> > + return;
> > +
> > + /* Check if we can accept more frames from client. */
> > + if ((self->tx_sdu_busy) &&
> > + (skb_queue_len(&self->tx_queue) < TTP_TX_LOW_THRESHOLD) &&
> > + (!self->close_pend)) {
> > + if (self->notify.flow_indication)
> > + self->notify.flow_indication(self->notify.instance,
> > + self, FLOW_START);
> > +
> > + /* self->tx_sdu_busy is the state of the client.
> > + * We don't really have a race here, but it's always safer
> > + * to update our state after the client - Jean II */
> > + self->tx_sdu_busy = FALSE;
> > + }
> > +}
> > +
> >
> > /*
> > * Function irttp_open_tsap (stsap, notify)
> > @@ -402,6 +425,8 @@ struct tsap_cb *irttp_open_tsap(__u8 stsap_sel, int credit, notify_t *notify)
> > self->todo_timer.data = (unsigned long) self;
> > self->todo_timer.function = &irttp_todo_expired;
> >
> > + INIT_WORK(&self->irnet_flow_work, irttp_flow_restart);
> > +
> > /* Initialize callbacks for IrLMP to use */
> > irda_notify_init(&ttp_notify);
> > ttp_notify.connect_confirm = irttp_connect_confirm;
> > @@ -761,25 +786,10 @@ static void irttp_run_tx_queue(struct tsap_cb *self)
> > self->stats.tx_packets++;
> > }
> >
> > - /* Check if we can accept more frames from client.
> > - * We don't want to wait until the todo timer to do that, and we
> > - * can't use tasklets (grr...), so we are obliged to give control
> > - * to client. That's ok, this test will be true not too often
> > - * (max once per LAP window) and we are called from places
> > - * where we can spend a bit of time doing stuff. - Jean II */
> > if ((self->tx_sdu_busy) &&
> > (skb_queue_len(&self->tx_queue) < TTP_TX_LOW_THRESHOLD) &&
> > (!self->close_pend))
> > - {
> > - if (self->notify.flow_indication)
> > - self->notify.flow_indication(self->notify.instance,
> > - self, FLOW_START);
> > -
> > - /* self->tx_sdu_busy is the state of the client.
> > - * We don't really have a race here, but it's always safer
> > - * to update our state after the client - Jean II */
> > - self->tx_sdu_busy = FALSE;
> > - }
> > + schedule_work(&self->irnet_flow_work);
> >
> > /* Reset lock */
> > self->tx_queue_lock = 0;
> >
> >
> >
>
> ---------------------------------
> Guennadi Liakhovetski, Ph.D.
> DSA Daten- und Systemtechnik GmbH
> Pascalstr. 28
> D-52076 Aachen
> Germany
>
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