----- Original Message ----- 
From: "John Baldwin" <[EMAIL PROTECTED]>
To: "John Baldwin" <[EMAIL PROTECTED]>
Cc: "FreeBSD current users" <[EMAIL PROTECTED]>; "FreeBSD current users"
Sent: Tuesday, July 09, 2002 8:40 PM
Subject: RE: userret() , ast() and the end of syscalls

> On 09-Jul-2002 John Baldwin wrote:
> > 
> > On 09-Jul-2002 Julian Elischer wrote:
> >> 
> >> A question to those who know..
> >> 
> >> why is userret() called both at the end of trap() or syscall()
> >> and also almost immediatly again (often) at the end of ast().
> > 
> > ast() is really a special form of a trap that is triggered by doing
> > a last-minute type check on return to userland to see if we still
> > have work to do.
> > 
> >> It seems that really there is no one place that one can put code that will
> >> be called ONCE and ONLY ONCE as a thread progresses to userland.
> > 
> > Sure there is.  When you want an action done, set a thread flag marking
> > the request and set TDF_ASTPENDING.  Then handle it in ast() if the flag
> > is set.
> Or, if this needs to happen on every return and not conditionally,
> then do it in userret() and use the state of a variable or some flag
> to note when you've already done it.
> -- 
> John Baldwin <[EMAIL PROTECTED]>  <><  http://www.FreeBSD.org/~jhb/
> "Power Users Use the Power to Serve!"  -  http://www.FreeBSD.org/

hope this won't increase per-thread memory requirement, I would like
to create more threads using same memory size. :)

David Xu

Do You Yahoo!?
Sign up for SBC Yahoo! Dial - First Month Free

To Unsubscribe: send mail to [EMAIL PROTECTED]
with "unsubscribe freebsd-current" in the body of the message

Reply via email to