On Mon, 2019-03-25 at 17:24 +0100, Arnd Bergmann wrote: > On Mon, Mar 25, 2019 at 5:19 PM James Bottomley > <James.Bottomley@xxxxxxxxxxxxxxxxxxxxx> wrote: > > > > --- a/fs/io_uring.c > > > +++ b/fs/io_uring.c > > > @@ -1968,7 +1968,15 @@ static int io_cqring_wait(struct > > > io_ring_ctx > > > *ctx, int min_events, > > > return 0; > > > > > > if (sig) { > > > - ret = set_user_sigmask(sig, &ksigmask, &sigsaved, > > > sigsz); > > > +#ifdef CONFIG_COMPAT > > > + if (in_compat_syscall()) > > > + ret = set_compat_user_sigmask((const > > > compat_sigset_t __user *)sig, > > > + &ksigmask, > > > &sigsaved, sigsz); > > > + else > > > +#endif > > > > This looks a bit suboptimal: shouldn't in_compat_syscall() be hard > > coded to return 0 if CONFIG_COMPAT isn't defined? That way the > > compiler can do the correct optimization and we don't have to > > litter #ifdefs and worry about undefined variables and other > > things. > > The check can be outside of the #ifdef, but set_compat_user_sigmask > is not declared then. Right, but shouldn't it be declared? I thought BUILD_BUG_ON had nice magic that allowed it to work here (meaning if the compiler doesn't eliminate the branch we get a build bug). > I think for the future we can consider just moving the compat logic > into set_user_sigmask(), which would simplify most of the callers, > but that seemed to invasive as a bugfix for 5.1. Well, that too. I've just been on a recent bender to stop #ifdefs after I saw what some people were doing with them. James