From mboxrd@z Thu Jan  1 00:00:00 1970
From: Andrew Cooper <andrew.cooper3@citrix.com>
Subject: Re: [PATCH v2 for-4.6 3/3] tools/libxl: Only continue
 stream operations if the stream is still in progress
Date: Tue, 28 Jul 2015 16:21:14 +0100
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To: Ian Jackson <Ian.Jackson@eu.citrix.com>
Cc: Wei Liu <wei.liu2@citrix.com>, Ian Campbell <Ian.Campbell@citrix.com>, Xen-devel <xen-devel@lists.xen.org>
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On 28/07/15 16:12, Ian Jackson wrote:
> Andrew Cooper writes ("Re: [PATCH v2 for-4.6 3/3] tools/libxl: Only continue stream operations if the stream is still in progress"):
>> Imagine a scenario whereby some error has occured and
>> check_all_finished() has _abort()'ed the tasks, but the save helper was
>> already on the way out, signalling success.
> ...
>> It is only save to stream_continue() if the stream is currently in use,
>> which is not a guaranteed situation in this function even if rc is 0.

erm s/save/safe/

> Hrm.  Yes.
>
> What do you think about putting the inuse check in stream_continue ?

That would work on the stream_read side but not the stream_write side,
but is not really correct IMO.

The _inuse() check is needed because the save helper callback is not
sure whether the stream is in use or not.  This is a property of the
save helper callback, rather than the stream.

Pushing the _inuse() check into the next layer would function, but it
adds extra _inuse() checks to other codepaths which should be fatal if
they failed in other contexts.

Would resubmitting with extra comments explaining this suffice?

~Andrew