Messages in this thread | | | Date | Mon, 23 Mar 2015 11:34:34 -0600 | From | David Ahern <> | Subject | Re: 4.0.0-rc4: panic in free_block |
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On 3/23/15 10:25 AM, David Miller wrote: > [PATCH] sparc64: Fix several bugs in memmove(). > > Firstly, handle zero length calls properly. Believe it or not there > are a few of these happening during early boot. > > Next, we can't just drop to a memcpy() call in the forward copy case > where dst <= src. The reason is that the cache initializing stores > used in the Niagara memcpy() implementations can end up clearing out > cache lines before we've sourced their original contents completely. > > For example, considering NG4memcpy, the main unrolled loop begins like > this: > > load src + 0x00 > load src + 0x08 > load src + 0x10 > load src + 0x18 > load src + 0x20 > store dst + 0x00 > > Assume dst is 64 byte aligned and let's say that dst is src - 8 for > this memcpy() call. That store at the end there is the one to the > first line in the cache line, thus clearing the whole line, which thus > clobbers "src + 0x28" before it even gets loaded. > > To avoid this, just fall through to a simple copy only mildly > optimized for the case where src and dst are 8 byte aligned and the > length is a multiple of 8 as well. We could get fancy and call > GENmemcpy() but this is good enough for how this thing is actually > used. > > Reported-by: David Ahern <david.ahern@oracle.com> > Reported-by: Bob Picco <bpicco@meloft.net> > Signed-off-by: David S. Miller <davem@davemloft.net>
seems like a formality at this point, but this resolves the panic on the M7-based ldom and baremetal. The T5-8 failed to boot, but it could be a different problem.
Thanks for the fast turnaround, David
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