Date: Thu, 18 Dec 2008 01:20:03 GMT From: Sean Bruno <sbruno@miralink.com> To: freebsd-bugs@FreeBSD.org Subject: Re: kern/118093: firewire bus reset hogs CPU, causing data to be lost Message-ID: <200812180120.mBI1K3Ye048523@freefall.freebsd.org>
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The following reply was made to PR kern/118093; it has been noted by GNATS.
From: Sean Bruno <sbruno@miralink.com>
To: "M. Warner Losh" <imp@bsdimp.com>
Cc: freebsd@sopwith.solgatos.com, freebsd-firewire@freebsd.org,
bug-followup@freebsd.org
Subject: Re: kern/118093: firewire bus reset hogs CPU, causing data to be
lost
Date: Wed, 17 Dec 2008 17:10:53 -0800
M. Warner Losh wrote:
> In message: <200812170329.DAA17848@sopwith.solgatos.com>
> Dieter <freebsd@sopwith.solgatos.com> writes:
> : Sean> Which file in dev/firewire are you looking at?
> :
> : fwohci.c and firewire.c
> :
> : examples:
> :
> : printf("non CYCLEMASTER mode\n");
> :
> : device_printf(fc->dev, "Initiate bus reset\n");
> :
> : -------------------
> :
> : Warner> This can't be the case. There's no SPL involved at all. Maybe
> : Warner> removing the printfs causes an interrupt to be serviced faster,
> : Warner> resulting in what appears to be better performance...
> :
> : With the printfs, Ethernet is not getting serviced. This
> : is repeatable and easily reproduced. Without the printfs,
> : it seems ok.
> :
> : If it isn't spl, what is locking out Ethernet?
>
> interrupt storm? In old-spl-locked drivers, often times the interrupt
> would be masked while certain operations happened. In new
> mutex-locked freebsd, there's no way to block the interrupts, so
> sometimes old code gets into an interrupt storm, which starves other
> things. Not sure why printf would trigger this, however...
>
> Warner
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>
Let me take a stab at this one this week. There's got to be something
more going on
than a printf() causing hell. It could be a mutex being held causing
nightmares.
The firewire code is my current project, I'll look at this issue now.
Sean
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