svn commit: r208988 - in head/sys: kern sys

[Julian Elischer]

On 6/11/10 6:43 AM, John Baldwin wrote:
> On Friday 11 June 2010 8:41:49 am Kostik Belousov wrote:
>> On Fri, Jun 11, 2010 at 08:10:40AM -0400, John Baldwin wrote:
>>> On Friday 11 June 2010 4:31:37 am Kostik Belousov wrote:
>>>> On Thu, Jun 10, 2010 at 04:14:05PM +0000, Alexander Motin wrote:
>>>>> Author: mav
>>>>> Date: Thu Jun 10 16:14:05 2010
>>>>> New Revision: 208988
>>>>> URL: http://svn.freebsd.org/changeset/base/208988
>>>>>
>>>>> Log:
>>>>>    Store interrupt trap frame into struct thread. It allows interrupt
>>> handler
>>>>>    to obtain both trap frame and opaque argument submitted on registrction.
>>>>>    After kernel and all drivers get used to it, legacy hack can be removed.
>>>>>
>>>>>    Reviewed by:	jhb@
>>>> Just curious, why td_frame is not enough for your usage ? I believe td_frame
>>>> is currently set only by traps and syscalls, and copied on forks.
>>>
>>> td_frame is not set on a nested interrupt.  Thus, if you use td_frame and get
>>> an interrupt while in a syscall, statclock() would account the time as a user
>>> tick instead of a system tick.
>>>
>>> Put another way, td_frame always references the user -->  system
>>> trapframe, but td_intr_frame will reference the most recent trapframe
>>> on the stack.
>>
>> I mean, save old td_frame on the interrupt, and assign interrupt trap
>> frame to td_frame. I.e., do what r208988, but replace td_intr_frame
>> with td_frame.
>
> Hmmm, I had thought there were reasons that was not safe, but after looking
> it may be safe to do this.
>

I THINK it is OK but make sure you add good comments everywhere.