On Thu, Apr 30, 2015 at 09:19:54PM -0700, Palmer Dabbelt wrote: > I ran across what I believe is a bug in some asm-generic code while > working on the RISC-V Linux port. Essentially the problem is that > wait_on_bit() takes a void *, but then perfroms long-aligned > operation. As far as I can tell, this bug could manifest on any other > architecture that doesn't support misaligned operations and uses this > particular asm-generic implementation. > > The patch set is split into three parts: > > * #1 fixes the bug by making task_struct.jobctl an unsigned long, > which ensures wait_on_bit() always ends up with a long-aligned > argument. > > * #2 changes the prototype of wait_on_bit() and friends to take a > "unsigned long *" instead of a "void *", with the intent of > ensuring these problems don't happen again. > > * #3 is a bit more intrusive: it goes and changes all uses of > task_struct.jobctl from int to long. > > I'm not sure if #3 has gone too far, but I think #1 and #2 are sane. > The cost is making task_struct larger on machines where > sizeof(long)>sizeof(int), but since it's so big already this isn't too > much cost. I thought about making test_bit() perform byte-aligned > accesses to avoid this cost, but since there are very similar looking > atomic functions I thought that would be too odd.
Fair enough. Thanks! -- 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/