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[Xen-devel] [PATCH 0 of 4] libxl: improve error handling when device mod

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Subject: [Xen-devel] [PATCH 0 of 4] libxl: improve error handling when device model fails to start early on
From: Ian Campbell <ian.campbell@xxxxxxxxxx>
Date: Wed, 4 May 2011 15:51:08 +0100
Cc: Bastian Blank <waldi@xxxxxxxxxx>
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Currently when the device model fails to start there is a delay until
we timeout and report error, some users have misinterpretted this
delay as a hang.

To improve this firstly we can add an access(2) sanity check on the
device model binary before doing anything.

Secondly we can propagate child failures to the parent much quicker by
adding a pipe between the intermediate process (which blocks in
waitpid() on the child until libxl__spawn_detach is called or the
child exits) to allow failure to be reported immediately and with a
slightly more specific error message.

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