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. -- 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/
