From: j0hnchann@h0me.net (John Chann)
Subject: Re: SCSI disk problems - Don't know where to begin
Date: 1998/10/28
Date: 1998-10-28T00:00:00+00:00 [thread overview]
Message-ID: <weAZ1.800$ps1.3486811@news.rdc1.sfba.home.com> (raw)
In-Reply-To: 70qtu7$7ua$1@nnrp1.dejanews.com
In article <70qtu7$7ua$1@nnrp1.dejanews.com>, jhassett@my-dejanews.com wrote:
>In article <70lj95$s66$1@nnrp1.dejanews.com>,
> krichey@nswc.navy.mil wrote:
>> I am writing some data extraction code in Ada (Greenhills) in a VxWorks,
>> PowerPC, VME card cage system, with a SCSI disk. VME-167 cards
>> Also there are some C tasks.
>>
>> At some point (it varies, and doesn't happen every time) the best we can tell
>> our SCSI disk is waiting on an interrupt and hanging. My Ada task is
>> just sitting there taking minutes for individual i/o statements to complete.
>
>A couple of our projects are working with Green Hills Ada and VxWorks,
>and PowerPC is one of their targets. I've heard that the restrictions
>imposed on interrupt services routines by VxWorks lead to serious
>limitations on any Ada subprograms called in the interrupt state.
>Perhaps you know about this, but just in case you don't, here is my
>understanding of the situation:
>
>Under VxWorks, interrupts are handled outside of any (VxWorks) task's
>context. This is evidently done to avoid the overhead of task context
>switching. Unfortunately, the Green Hills Ada compiler seems to be
>designed with the assumption that there is always a task ID available,
>but this is not true in the interrupt state. Besides the usual
>restrictions imposed by VxWorks (no blocking operations, no I/O through
>device drivers, no FP coprocessor operations), we've been told by
>Green Hills that subprograms called in the interrupt state must not
>have exception handlers, and must be compiled with runtime checks
>suppressed. Apparently there are attempts to access the task control
>block when setting up exception handling or when preparing to do the
>runtime checks.
>
>I have no idea whether a failure to comply with these restrictions could
>lead to the symptoms you've seen, but you need to know about this in any
>case.
>
>- Jim Hassett
Please be aware that ISRs in vxWorks should be as short as possible, most ISRs
just handle the hardware and grab volatile data then release a high priority
task with a semGive then exit. Holding the system in the ISR whilst you
contemplate your navel destroys determinism and blocks other IRQs at the same
or lower priority.
I'd be very very surprised if Green Hills didn't have some very good advice
in this area.
To return specifically to the original question; if you want to know where
your system has gone off to hide then I suggest you try WindView which will
show you what is going on.
JRC
John Chann
California, USA
prev parent reply other threads:[~1998-10-28 0:00 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
1998-10-21 0:00 SCSI disk problems - Don't know where to begin krichey
1998-10-22 0:00 ` dennison
1998-10-23 0:00 ` jhassett
1998-10-28 0:00 ` John Chann [this message]
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