On Fri, 2016-04-15 at 15:02 -0500, Josh Poimboeuf wrote:
> On Fri, Apr 15, 2016 at 12:05:26PM -0700, James Bottomley wrote:
> > On Fri, 2016-04-15 at 20:56 +0200, Denys Vlasenko wrote:
> > > and now *many* users of qla2x00 and new-ish gcc are going to
> > > very much notice it, as their kernels will start crashing
> > > reliably.
> > >
> > > The commits can be reverted, sure, but they per se do not contain
> > > anything unusual. They, together with not very typical construct
> > > in qla2x00_get_host_fabric_name, one
> > > which boils down to "swab64p(constant_array_of_8_bytes)",
> > > just happen to nudge gcc in a right way to finally trigger the
> > > bug.
> > >
> > > So I came with another idea how to forestall the imminent deluge
> > > of
> > > qla2x00 oops reports - this patch.
> >
> > There are actually a raft of checkers that run the upstream code
> > which
> > aren't seeing any problem; likely because the code is harder to
> > trigger
> > than you think. So, lets wait until the resolution of the other
> > thread
> > before we panic, especially since we're only at -rc3.
>
> Regardless of the outcome of the gcc bug, it seems kind of silly to
> byteswap a constant value of 0xffffffffffffffff.
>
> uint8_t node_name[WWN_SIZE] = { 0xFF, 0xFF, 0xFF, 0xFF, \
> 0xFF, 0xFF, 0xFF, 0xFF};
> u64 fabric_name = wwn_to_u64(node_name);
>
> Similar to what Denys suggested, it can just be:
>
> u64 fabric_name = -1;
> or
> u64 fabric_name = 0xffffffffffffffff;
>
> Wouldn't that be an improvement to the code regardless?
"Improvement" would be in the eye of the beholder. Semantically it
would be wrong because we're initialising a CPU local representation of
a big endian structure, so we *should* use the conversion.
James
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