RE: [Linux-ia64] re-enabling interrupts and interrupt collect

From: Mallick, Asit K <asit.k.mallick_at_intel.com>
Date: 2000-11-09 05:37:59
Setting the PSR.ic or PSR.i is not implicitly serialized and setting both
PSR.ic and PSR.i in a single instruction could create a timing window where
PSR.ic=0 and PSR.i=1. So, software must set the PSR.ic explicitly before
setting the PSR.i.

Asit


> -----Original Message-----
> From: Chuck Fleckenstein [mailto:cfleck@co.intel.com]
> Sent: Wednesday, November 08, 2000 2:07 AM
> To: Jonathan Case Nicklin
> Cc: linux-ia64@ia64linux.org
> Subject: Re: [Linux-ia64] re-enabling interrupts and interrupt collect
> 
> 
> Since the ssm of psr.i does not require serialization then I 
> believe this
> would
> be expected.
> 
> so as you said the guaranteed method of safely reenabling ic 
> and i would
> be:
> 
>     ssm psr.ic
>     ;;
>     srlz.d
>     ssm psr.i
> 
> 
> Chuck
> 
> 
> Jonathan Case Nicklin wrote:
> 
> > All,
> >
> > Recently, i was working on a section of code that disabled/enable
> > interrupts
> > and interrupt collection like so.
> >
> >     rsm psr.i | psr.ic
> >     ;;
> >     ... //body
> >     ;;
> >     ssm psr.i | psr.ic
> >     ;;
> >     srlz.d
> >     ;;
> >
> > I found however that this implementation did not work under 
> heavy loads.
> >
> > It took a while to figure out that a pending interrupt that 
> had occurred
> >
> > in the body of code, executed while interrupts were turned off, was
> > delivered
> > after the ssm call as expected. However, it was delivered 
> before the ic
> > bit
> > serialized. In the code this caused undesirable results. I 
> found that
> > the
> > proper way to implement the above is to re-enable the ic bit and
> > serialize
> > before re-enabling the interrupt bit. Has anyone else come 
> across this
> > problem and can anybody shed some light on whether this is 
> the expected
> > operation.
> >
> > Sincerely,
> > Jonathan Case Nicklin
> >
> > Mission Critical Linux
> > www.missioncriticallinux.com
> >
> > ps. The manual gives an example of the implementation that 
> works, but
> > does
> > not provide any explanation of implementation itself (as 
> far as I can
> > see ;-P )
> >
> > _______________________________________________
> > Linux-IA64 mailing list
> > Linux-IA64@linuxia64.org
> > http://lists.linuxia64.org/lists/listinfo/linux-ia64
> 
> 
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> Linux-IA64@linuxia64.org
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> 
Received on Wed Nov 08 10:38:21 2000

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