poll()/select()

[Konstantin Prokazoff]

Welcome,

    John, thanks for the answer. I'll test today bus_setup_intr() without
INTR_FAST flag, but how I remember, this cause to system heavy load for
interrupt processing ;( in my case.
    My handler uses spin mutexes to block inter-interrupting & sleep mutexes
to block some structures now. I have tried to use swi/taskqueue, but result
is a "sync" degradation level.
    Can you help with sources briefing in my driver case?
    Thnx in advance.

Best regards,
        Konstantin Prokazoff
Center Of Excellence, S_V_R Ltd., Kyiv HQs, Ukraine
Official business-partner & DevConnect member of Avaya Inc.
Regional development & support center of Digium Inc.
Tel. +38 044 594 1781, ext. 1038
Fax. +38 044 234 0455

----- Original Message ----- 
From: "John Baldwin" <jhb at freebsd.org>
To: <freebsd-hackers at freebsd.org>
Cc: "Konstantin Prokazoff" <kprokazov at svr.kiev.ua>
Sent: Monday, November 21, 2005 5:38 PM
Subject: Re: poll()/select()


> On Monday 21 November 2005 08:14 am, Konstantin Prokazoff wrote:
> > Thanks for comment,
> >
> >     I think, after kernel inspection, problem (maybe) in preemption.
While
> > syscall to poll or select holds sellock, and if another thread (process)
> > tries to syscall or we have taken interrupt (where handler use
> > selrecord/selwakeup too), kernel will deadlock.
> >     I have this situation cause to INTR_FAST interrupt handler in device
> > driver for Digium's PCI board, which provides 4 T1/E1 interfaces.
Problem
> > 100% repetitive.
> >     Another way to avoid such deadlock - provide different
kthread/ithreads
> > for select/poll mechanism.
>
> You can't call selwakeup() from an INTR_FAST handler.  Try removing
INTR_FAST
> and see if it fixes your issue.  If you want to use INTR_FAST, then
realize
> that you can only use spin mutexes in your handler, and that any more
> complicated work like selwakeup() that uses regular mutexes will have to
be
> deferred either by using a swi handler or dispatching a task to the Fast
> taskqueue.
>
> -- 
> John Baldwin <jhb at FreeBSD.org>  <><  http://www.FreeBSD.org/~jhb/
> "Power Users Use the Power to Serve"  =  http://www.FreeBSD.org