>> On x86, the case that msword >= divsor causes a divide exception >> (divide ba generalization of divide by zero), so it's tempting >> to do the same sort of "assume no trap and fix up in the handler" >> trick as <asm/uaccess.h>.
> That would be horrible. One of the reasonably common cases of do_div() > is for printing out numbers. And they are often in the 4G+ range.. Actually, printing numbers is *not* such an instance; I've had my fingers in lib/vsprintf.c, and since the divisor is constant, it uses reciprocal multiplies. The only instance of do_div in lib/vsprintf.c is in a version of put_dec() which is used only if BITS_PER_LONG == 64. If bits_per_long == 32, it uses a neat hack due to Douglas Jones which avoids using divide instructions entirely! (Commit 133fd9f5cd if you are curious.) The hot paths with 64-bit results are in the block layer and RAID code, and that's why I wasn't seriously suggesting replacing *all* instances; it was more of a static code size diet hack. (It's also not likely worth the maintenance burden of the additional code subtlety. "Tempting" is not necessarily a good idea.) -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/