if_start running deferred for Giant

Tofig Suleymanov tofig at freebsd.az
Sun Dec 30 13:26:11 PST 2007

Robert Watson wrote:
> On Sun, 30 Dec 2007, Tofig Suleymanov wrote:
>> I am writing a driver for Kyocera USB modem for FreeBSD and there are 
>> a few questions that I am not able to solve alone. I would be 
>> grateful if someone could point me into the right direction.Here is 
>> the first one:
>> Inside the USB_ATTACH() function I initialise the ifnet(9) structure 
>> and return USB_ATTACH_SUCCESS_RETURN. Everything seems to be fine so 
>> far (I can see the interface in ifconfig output) except the following 
>> error notice spit to the console:
>> xxxxxx kernel: ib0: if_start running deferred for Giant
>> I am not sure what does this exactly mean.
>> Any help would be appreciated.
> This occurs when a network device driver has declared itself 
> IFF_NEEDSGIANT -- that is, has declared that it requires the Giant 
> lock in order to operate. As this is considered an undesirable state 
> of affairs for a device driver, a warning is printed. However, in the 
> case of a USB device driver, it is currently required as the USB 
> framework is not MPSAFE, so requires Giant.
> Robert N M Watson
> Computer Laboratory
> University of Cambridge
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Thanks for clarification. Does it mean that I can ignore this notice 
when dealing with USB framework ?

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