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CVS commit: src/sys/arch/xen/xen

Module Name:    src
Committed By:   jym
Date:           Thu Nov 24 01:47:18 UTC 2011

Modified Files:
        src/sys/arch/xen/xen: xbdback_xenbus.c

Log Message:
Deep rework of the xbdback(4) driver; it now uses a thread per instance
instead of continuations directly from shm callbacks or interrupt
handlers. The whole CPS design remains but is adapted to cope with
a thread model.

This patch allows scheduling away I/O requests of domains that behave
abnormally, or even destroy them if there is a need to (without thrashing
dom0 with lots of error messages at IPL_BIO).

I took this opportunity to make the driver MPSAFE, so multiple instances
can run concurrently. Moved from home-grown pool(9) queues to
pool_cache(9), and rework the callback mechanism so that it delegates
I/O processing to thread instead of handling it itself through the
continuation trampoline.

This one fixes the potential DoS many have seen in a dom0 when trying to
suspend a NetBSD domU with a corrupted I/O ring.

Benchmarks ( release runs and bonnie++) do not show any
performance regression, the "new" driver is on-par with the "old" one.

ok bouyer@.

To generate a diff of this commit:
cvs rdiff -u -r1.51 -r1.52 src/sys/arch/xen/xen/xbdback_xenbus.c

Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.

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