[head tinderbox] failure on mips/mips

M. Warner Losh imp at bsdimp.com
Wed Feb 18 14:46:01 PST 2009

In message: <499C8396.2020000 at incunabulum.net>
            Bruce Simpson <bms at incunabulum.net> writes:
: M. Warner Losh wrote:
: > ...
: > : The point being that programmers *do* code with certain
: > : assumptions and as soon as those assumptions don't hold on
: > : a platform, you end up worse off. My thoughts for MIPS n32
: > : are to make it behave like any "normal" 32-bit strong-
: > : alignment platform to avoid 1) a large number of runtime
: > : alignment faults -- which are a bigger performance bottleneck
: > : than forcing 64-bit integrals to be accessed with 2 32-bit
: > : accesses
: >   
: FWIW, Linux use a type-length-value protocol for the netlink routing 
: socket, so alignment issues of this kind are shifted around (forgive the 
: pun).

FreeBSD does too for the most part, but it is only at the inter-message
level, not intra-message.

: > It also turns out that in this case, a simple (void *) is safe and
: > causes no issues because that time_t isn't accessed...  It does give
: > one time to pause and think about it.
: >   
: Yes, the void * cast works around the issue for now, but doesn't offer 
: any guarantees that we are doing the right thing on strict alignment 
: architectures.
: If the alignment *is* invalid, then we take the hit.

Right.  The compiler doesn't check it, but I just did and things are
fine given the fields accessed.

But its that last bit that's the problem...

I also have changed the offending line in my tree to be u_long instead
of time_t since that is a better match to the protocol, and also gives
us 168 years of uptime before there's an issue.


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