Date: Wed, 30 Apr 2003 09:52:15 -0600 (MDT) From: "M. Warner Losh" <imp@bsdimp.com> To: phk@phk.freebsd.dk Cc: freebsd-arch@freebsd.org Subject: Re: lots of malloc(M_WAITOK)'s in interrupt context from camisr Message-ID: <20030430.095215.48529965.imp@bsdimp.com> In-Reply-To: <12432.1051717236@critter.freebsd.dk> References: <16047.59842.60959.352839@grasshopper.cs.duke.edu> <12432.1051717236@critter.freebsd.dk>
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In message: <12432.1051717236@critter.freebsd.dk>
"Poul-Henning Kamp" <phk@phk.freebsd.dk> writes:
: In message <16047.59842.60959.352839@grasshopper.cs.duke.edu>, Andrew Gallatin
: writes:
: >
: >Poul-Henning Kamp writes:
: > > In message <16047.59314.532227.475952@grasshopper.cs.duke.edu>, Andrew Gallatin
: > > writes:
: > > >
: > > >John Baldwin writes:
: > > >
: > > > > If you need to do more work in your interrupt routine than just wakeups
: > > > > and dinking with registers, you can always wake up a software interrupt
: > > > > handler or some other random kthread to do things that take a long amount
: > > >
: > > >Dumb question: Exactly what is one allowed to do in an INTR_FAST
: > > >interrupt context? Obviously, you can't sleep. But can you call
: > > >wakeup()?
: > >
: > > Calling wakeup() is just about it, but we should actually define it
: > > more precisely in a suitable man-page.
: >
: >That would be cool. Since wakeup() uses a spinlock, I assume that
: >spinlocks are generally OK too..
:
: I'm not sure you should infer too much yet...
Yes. A spinlock in the context of wakeup being safe might be
radically different than spinlocks generally being safe.
I'm not sure that wakeup is safe in a fast interrupt context even.
I've always had to create a soft interrupt and call the sched routine
to get it to run.
We definitely need to document what's allowed in a fast interrupt
handler. Generally as little as possible to placate the hardware and
the 'expensive' parts of the driver should be in a soft interrupt
thread.
Warner
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