[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-devel] Re: [PATCH] libxl: initialize domid to 0 in libxl__create_stubdom
On Thu, 2011-06-09 at 12:03 +0100, Wei Liu wrote: > On Thu, 2011-06-09 at 11:23 +0100, Ian Campbell wrote: > > On Thu, 2011-06-09 at 09:31 +0100, Wei Liu wrote: > > > On Thu, 2011-06-09 at 08:55 +0100, Ian Campbell wrote: > > > > On Thu, 2011-06-09 at 06:03 +0100, Wei Liu wrote: > > > > > The uninitialized domid may cause libxl__domain_make to fail. > > > > > > > > > > In libxl__domain_make: > > > > > assert(!libxl_domid_valid_guest(*domid)). > > > > > > > > > > Signed-off-by: Wei Liu <liuw@xxxxxxxxx> > > > > > > > > That check seems pretty odd to me at first but the commit message of > > > > 22842:ccfa0527893e does a good job of explaining why so: > > > > > > > > Acked-by: Ian Campbell <ian.campbell@xxxxxxxxxx> > > > > > > > > although it's not clear why libxl__domain_make doesn't just set an > > > > invalid value as it's first act and save the callers the effort, the net > > > > result would still be the correct semantics for libxl_domid_valid_guest > > > > when the function exits. > > > > > > > > > > I think the commit message of 22842:ccfa0527893e says pretty clear that > > > it is caller's responsibility to initialize domid to a invalid value. > > > > Only because that's how 22842 causes libxl__make_domain to be > > implemented, we are free to change it. > > > > I'm not against changing it. But I won't do this until I completely > understand what it does and why it does. Sure. I think your patch is fine as it is, I was just wondering about the wider context... > > My patch is based on similar use case in > libxc_create.c:do_domain_create, which initializes domid to 0 before > calling libxl__domain_make. That's safer (not likely to misunderstand > its usage and introduce new bug) and solve my problem. > > > > However, libxl__make_domain sets domid=-1 a few lines after the check. > > > This confuses me. > > > > Yeah, me too, that line could just be hoisted up to the first thing the > > function does with no loss of safety AFAICT. > > > > Ian. > > > > _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-devel
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