xen/intr: add channel closing in case of early setup failure

[ehem_freebsd_m5p.com]

Summary

xen_intr_bind_isrc() will now close event channels if the source is
marked in all cases. This means callers no longer need to handle
closing of channels if xen_intr_bind_isrc() fails.

[mhorne]

sys/xen/xen_intr.c

470–471 ↗

(On Diff #100488)

This is particularly ugly. A goto into a loop is not acceptable.

[ehem_freebsd_m5p.com]

sys/xen/xen_intr.c

470–471 ↗

(On Diff #100488)

I was trying to figure out how best to express this. Problem was having a goto failcomm; after failrelease: seemed kind of ugly too.

[ehem_freebsd_m5p.com]

sys/xen/xen_intr.c

470–471 ↗

(On Diff #100488)

Oh, the other option is doing a if(isrc) and hope the compiler optimizes the conditional out.

[ehem_freebsd_m5p.com]

Updating to current tree status.

[ehem_freebsd_m5p.com]

Eventually when this had sufficient looking at only the two spots before the allocation need a special case. Once the allocation is done, xen_intr_release_isrc() adequately handles channel shutdown. As such this resolves @mhorne's comment.

[ehem_freebsd_m5p.com]

Due to coming up with an alternative approach, this appears certain to disappear.