Why use `thread' as an argument of Syscalls?

[Daniel Eischen]

On Mon, 5 Jun 2006, MingyanGuo wrote:

> On 6/5/06, Daniel Eischen <deischen at freebsd.org> wrote:
>> 
>> On Mon, 5 Jun 2006, MingyanGuo wrote:
>> 
>> > Hi all,
>> >    I  find that  FreeBSD Syscalls  always have an `thread'
>> > argument, for example, preadv(/sys/kern/sys_generic.c)
>> > has a `td' argument.  But  some Syscalls may rarely  use
>> > this argument,  and  thay ( and functions they invoke) can
>> > get  the  `thread'  who  make  the  Syscall  _easily_  via
>> > `curthread' macro if  needed. So the `thread' argument
>> > seems not needed.
>> >  Can anybody tell me why use `thread' as an argument
>> > of Syscalls?
>> 
>> You could have asked "why use 'proc' as an argument of Syscalls"
>> 12 years ago (or more).  When the kernel became thread-aware
>> (almost 5 years ago), most 'struct proc' arguments were changed
>> to 'struct thread'.
>> 
>> --
>> DE
>> 
>
> They are the same questions, I think ;-). Now would
> you please explain  "why use `proc' as  an  argument
> of Syscalls"  to me :)?  I've  read some source code
> of the kernel, but no comments about it found.

I don't know.  Convention?  It makes sense to me.

-- 
DE