On 10/01/2013 11:07 PM, Tejun Heo wrote: > On Tue, Oct 01, 2013 at 05:03:48PM -0400, Tejun Heo wrote: >> On Tue, Oct 01, 2013 at 10:53:31PM +0200, Helge Deller wrote: >>> So, in summary my patch here is not really necessary, but for the sake of >>> clean code I think it doesn't hurt either and as such it would be nice if >>> you could apply it. >> >> What? function *must* take any value and try to access it and not >> cause failure. That's the *whole* purpose of that interface. How is >> having incomplete spurious checks around it "clean code" in any sense >> of the word? That doesn't make any sense. > > Just in case you didn't know already. probe_kernel_read()'s role is > to take any ulong value and dereference it if it can. If not, it can > return any value, but it shouldn't crash in any case. If you're just > adding NULL test in probe_kernel_read(), you're just masking a common > failure pattern and the kernel still *will* panic while dumping the > states. If a specific arch doesn't have proper probe_kernel_read() > implementation, adding if (!NULL) test there could be a temporary > workaround, but it should be clearly marked as such. Sure, probe_kernel_read() takes care that no segfaults will happen. Nevertheless, if we know that "pwq" might become NULL, why access pwq->wq at all? struct pool_workqueue *pwq = NULL; probe_kernel_read(&wq, &pwq>wq, sizeof(wq)); If you wouldn't have used probe_kernel_read() you would never code it like that. That's what I meant when I wrote "clean coding" (aka "similar to what you would have done without probe_kernel_read()"). Helge -- To unsubscribe from this list: send the line "unsubscribe linux-parisc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
