Arnd Bergmann <arnd@xxxxxxxx> writes: > On Wed, May 29, 2019 at 6:12 PM Oleg Nesterov <oleg@xxxxxxxxxx> wrote: >> >> Al, Linus, Eric, please help. >> >> The previous discussion was very confusing, we simply can not understand each >> other. >> >> To me everything looks very simple and clear, but perhaps I missed something >> obvious? Please correct me. > > Thanks for the elaborate explanation in this patch, it all starts making sense > to me now. I also looked at your patch in detail and thought I had found > a few mistakes at first but those all turned out to be mistakes in my reading. > >> See the compile-tested patch at the end. Of course, the new _xxx() helpers >> should be renamed somehow. fs/aio.c doesn't look right with or without this >> patch, but iiuc this is what it did before 854a6ed56839a. > > I think this is a nice simplification, but it would help not to mix up the > minimal regression fix with the rewrite of those functions. For the stable > kernels, I think we want just the addition of the 'bool interrupted' argument > to restore_user_sigmask() to close the race that was introduced > 854a6ed56839a. Following up on that for future kernels, your patch > improves the readability, but we can probably take it even further. > >> - ret = set_user_sigmask(ksig.sigmask, &ksigmask, &sigsaved, ksig.sigsetsize); >> + ret = set_xxx(ksig.sigmask, ksig.sigsetsize); >> if (ret) >> return ret; >> >> ret = do_io_getevents(ctx_id, min_nr, nr, events, timeout ? &ts : NULL); >> - restore_user_sigmask(ksig.sigmask, &sigsaved); >> - if (signal_pending(current) && !ret) >> + >> + interrupted = signal_pending(current); >> + update_xxx(interrupted); > > Maybe name this > > restore_saved_sigmask_if(!interrupted); > > and make restore_saved_sigmask_if() an inline function > next to restore_saved_sigmask()? > >> @@ -2201,13 +2205,15 @@ COMPAT_SYSCALL_DEFINE6(io_pgetevents, >> if (usig && copy_from_user(&ksig, usig, sizeof(ksig))) >> return -EFAULT; >> >> - ret = set_compat_user_sigmask(ksig.sigmask, &ksigmask, &sigsaved, ksig.sigsetsize); >> + ret = set_compat_xxx(ksig.sigmask, ksig.sigsetsize); >> if (ret) >> return ret; > > With some of the recent discussions about compat syscall handling, > I now think that we want to just fold set_compat_user_sigmask() > into set_user_sigmask() (whatever they get called in the end) > with an in_compat_syscall() conditional inside it, and completely get > rid of the COMPAT_SYSCALL_DEFINEx() definitions for those > system calls for which this is the only difference. > > Unfortunately we still need the time32/time64 distinction, but removing > syscall handlers is a significant cleanup here already, and we can > move most of the function body of sys_io_pgetevents() into > do_io_getevents() in the process. Same for some of the other calls. > > Not sure about the order of the cleanups, but probably something like > this would work: > > 1. fix the race (to be backported) > 2. unify set_compat_user_sigmask/set_user_sigmask > 3. remove unneeded compat handlers > 4. replace restore_user_sigmask with restore_saved_sigmask_if() > 5. also unify compat_get_fd_set()/get_fd_set() and kill off > compat select() variants. Are new system calls added preventing a revert of the patch in question for stable kernels? Eric
