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Re: [Qemu-devel] [PATCH 3/4] s390x/css: remove dubious error handling br
From: |
Cornelia Huck |
Subject: |
Re: [Qemu-devel] [PATCH 3/4] s390x/css: remove dubious error handling branch |
Date: |
Tue, 12 Sep 2017 16:05:01 +0200 |
On Mon, 11 Sep 2017 15:08:52 +0200
Halil Pasic <address@hidden> wrote:
> On 09/11/2017 11:48 AM, Cornelia Huck wrote:
> > On Fri, 8 Sep 2017 17:24:45 +0200
> > Halil Pasic <address@hidden> wrote:
> >> The case in question actually never happens. Let us get rid of the dead
> >> code.
> >
> > I had tried to be complete in my initial implementation. With the
> > current implementation, it can never happen, yes. We can easily
> > resurrect it from git history should we need it in the future.
> >
>
> I've tried to understand the branch but I failed. Weather the subchannel
> is busy or not should be already decided, and if the device is busy
> that is probably supposed to be indicated via device status (word 2 bit 3).
>
> So I wrote dubious because I could not figure it out. But unused
> is certainly nicer.
>
> I think shall the need emerge the preferred way of handling would
> be to use the custom handling (-EIO) branch.
What this is trying to do is deferred cc 1 handling. On a real system,
a ssch may return with cc 0 to indicate that the channel program has
been accepted; but when the channel subsystem actually tries to execute
it, a status is already pending. Basically, it's a race condition:
Therefore the 'deferred' cc 1.
Maybe I should have called this 'deferred subchannel busy'... but
anyway, this cannot happen in our current implementation.
- [Qemu-devel] [PATCH 0/4] s390x/css: ccw interpretation fixes, Halil Pasic, 2017/09/08
- [Qemu-devel] [PATCH 4/4] s390x/css: fix incorrect length indication, Halil Pasic, 2017/09/08
- Re: [Qemu-devel] [PATCH 4/4] s390x/css: fix incorrect length indication, Cornelia Huck, 2017/09/11
- Re: [Qemu-devel] [PATCH 4/4] s390x/css: fix incorrect length indication, Halil Pasic, 2017/09/11
- Re: [Qemu-devel] [PATCH 4/4] s390x/css: fix incorrect length indication, Cornelia Huck, 2017/09/12
- Re: [Qemu-devel] [PATCH 4/4] s390x/css: fix incorrect length indication, Halil Pasic, 2017/09/12
- Re: [Qemu-devel] [PATCH 4/4] s390x/css: fix incorrect length indication, Cornelia Huck, 2017/09/12
- Re: [Qemu-devel] [PATCH 4/4] s390x/css: fix incorrect length indication, Halil Pasic, 2017/09/12
- Re: [Qemu-devel] [PATCH 4/4] s390x/css: fix incorrect length indication, Cornelia Huck, 2017/09/13