Messages in this thread | | | Date | Fri, 15 Apr 2016 15:02:35 -0500 | From | Josh Poimboeuf <> | Subject | Re: [PATCH] qla2xxx: rewrite code to avoid hitting gcc bug 70646 |
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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?
-- Josh
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