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From: "Jan Beulich" <JBeulich@suse.com>
To: Wei Liu <wei.liu2@citrix.com>
Cc: George Dunlap <George.Dunlap@eu.citrix.com>,
	Paulina Szubarczyk <paulinaszubarczyk@gmail.com>,
	Ian Jackson <ian.jackson@eu.citrix.com>,
	Xen-devel <xen-devel@lists.xenproject.org>
Subject: Re: [PATCH] libxl: fix an error path that uses uninitialised rc in libxl_set_memory_target
Date: Wed, 22 Jun 2016 09:20:57 -0600	[thread overview]
Message-ID: <576AC8F902000078000F7BDB@prv-mh.provo.novell.com> (raw)
In-Reply-To: <20160622135934.GF1790@citrix.com>

>>> On 22.06.16 at 15:59, <wei.liu2@citrix.com> wrote:
> On Wed, Jun 22, 2016 at 07:53:56AM -0600, Jan Beulich wrote:
>> >>> On 22.06.16 at 15:47, <wei.liu2@citrix.com> wrote:
>> > On Wed, Jun 22, 2016 at 06:58:28AM -0600, Jan Beulich wrote:
>> >> >>> On 12.06.16 at 16:09, <wei.liu2@citrix.com> wrote:
>> >> > --- a/tools/libxl/libxl.c
>> >> > +++ b/tools/libxl/libxl.c
>> >> > @@ -4927,10 +4927,12 @@ retry_transaction:
>> >> >  
>> >> >      target = libxl__xs_read(gc, t, GCSPRINTF("%s/memory/target", 
> dompath));
>> >> >      if (!target && !domid) {
>> >> > -        if (!xs_transaction_end(ctx->xsh, t, 1))
>> >> > +        if (!xs_transaction_end(ctx->xsh, t, 1)) {
>> >> > +            rc = ERROR_FAIL;
>> >> 
>> >> I'm sorry for noticing this only now - is ERROR_FAIL the right thing
>> >> to use here, considering how things worked before the change that
>> >> introduced the issue getting fixed here? I had intentionally decided
>> >> to use ERROR_INVAL in the patch variant I did submit (as at that
>> >> time I wasn't yet aware of the other fix floating around already).
>> >> 
>> > 
>> > When I wrote this patch, I thought the return value should be tied to
>> > xs_transaction_end.
>> 
>> xs_transaction_end() returning zero means success afaict.
>> 
> 
> /* End a transaction.
>  * If abandon is true, transaction is discarded instead of committed.
>  * Returns false on failure: if errno == EAGAIN, you have to restart
>  * transaction.
>  */
> bool xs_transaction_end(struct xs_handle *h, xs_transaction_t t,
>                         bool abort);
> 
> I think you misread.

Indeed, I got mislead by "goto out_no_transaction". Yet that
doesn't change the discussion of the error - originally this didn't
return -1 here, but +1 (i.e. reflecting the surrounding if(), not
the inner one).

Jan


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  reply	other threads:[~2016-06-22 15:21 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-06-12 14:09 Wei Liu
2016-06-20 13:32 ` Ian Jackson
2016-06-22 12:58 ` Jan Beulich
2016-06-22 13:47   ` Wei Liu
2016-06-22 13:53     ` Jan Beulich
2016-06-22 13:59       ` Wei Liu
2016-06-22 15:20         ` Jan Beulich [this message]
2016-06-22 15:29           ` Wei Liu

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