Messages in this thread | | | Date | Tue, 23 Jun 2009 11:33:56 -0700 (PDT) | From | Linus Torvalds <> | Subject | Re: [GIT PULL] asm-generic fixes |
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On Tue, 23 Jun 2009, Arnd Bergmann wrote: > @@ -71,7 +75,7 @@ static unsigned int do_csum(const unsigned char *buff, int len) > if (count) { > unsigned long carry = 0; > do { > - unsigned long w = *(unsigned long *) buff; > + unsigned long w = *(unsigned int *) buff; > count--; > buff += 4; > result += carry;
I don't think this is sufficient.
You might need to make 'result', 'carry', and 'w' be 'unsigned int' too.
Why? Because the final folding is only doen from 32-bit to 16 bit, we don't do the whole 64-bit to 32-bit to 16-bit chain.
Now, it's possible (even likely) that even with a 64-bit word, we'll never actually do large enough areas that 'result' would ever have very many bits set in the 32+ bit region, and since we do end up folding to 16 bits twice (once after the loop and once at the end), it _probably_ gets things right in most cases. But I doubt "probably" is strong enough. Somebody should check.
Or just see arch/alpha/lib/checksum.c, which does the whole 64-bit case. Maybe lib/checksum.c should be lib/checksum_{32,64}.c.
Linus
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