netdev - Re: [PATCH] r8169: Fix irq masking in rtl8169

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Message-Id: <200903181300.00591.fzu@wemgehoertderstaat.de>
Date:	Wed, 18 Mar 2009 12:59:59 +0100
From:	Karsten Wiese <fzu@...gehoertderstaat.de>
To:	Francois Romieu <romieu@...zoreil.com>
Cc:	netdev@...r.kernel.org, Rafael Wysocki <rjw@...k.pl>
Subject: Re: [PATCH] r8169: Fix irq masking in rtl8169_interrupt()

Am Mittwoch 18 März 2009 schrieb Francois Romieu:
> Karsten Wiese <fzu@...gehoertderstaat.de> :
> > Am Dienstag 17 März 2009 schrieb Francois Romieu:
> [...]
> > > How the patch is supposed to work is not completely clear to me.
> > 
> > Without it, if netif_rx_schedule_prep() returns 0, __netif_rx_schedule() is not
> > called so nothing is there to care for the transfer. Nonetheless intr_mask is 
> > changed so that its not possible that __netif_rx_schedule() is ever called
> > later.
> > 
> > Patch works by letting rtl8169_interrupt() again call netif_rx_schedule_prep()
> > until it succeeds and __netif_rx_schedule() is called.
> 
> Thanks for the explanation.
> 
> If netif_rx_schedule fails after napi is enabled, there is a
> racing poll thread to care for the transfer.
> 
> Stated differently the bug is noticeable because napi_enable() 
> should be called before request_irq() in rtl8169_open, right ?

Propably yes. That would mean the first interrupt is received before
rtl_hw_start() is called in rtl8169_open. The source of that
interrupt would be something else then?

Thanks,
Karsten
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