kern/118093: firewire bus reset hogs CPU, causing data to be lost

M. Warner Losh imp at
Tue Dec 16 23:10:04 PST 2008

The following reply was made to PR kern/118093; it has been noted by GNATS.

From: "M. Warner Losh" <imp at>
To: freebsd at
Cc: freebsd-firewire at, freebsd-drivers at,
        bug-followup at
Subject: Re: kern/118093: firewire bus reset hogs CPU, causing data to be
Date: Tue, 16 Dec 2008 23:59:41 -0700 (MST)

 In message: <200812170329.DAA17848 at>
             Dieter <freebsd at> 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...

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