On 06/05, Linus Torvalds wrote: > > On Wed, Jun 5, 2019 at 8:58 AM Oleg Nesterov <oleg@xxxxxxxxxx> wrote: > > > > To simplify the review, please see the code with this patch applied. > > I am using epoll_pwait() as an example because it looks very simple. > > I like it. > > However. > > I think I'd like it even more if we just said "we don't need > restore_saved_sigmask AT ALL". ^^^^^^^^^^^^^^^^^^^^^ Did you mean restore_saved_sigmask_unless() introduced by this patch? If yes: > Which would be fairly easy to do with something like the attached... I don't think so, > --- a/arch/x86/entry/common.c > +++ b/arch/x86/entry/common.c > @@ -160,7 +160,7 @@ static void exit_to_usermode_loop(struct pt_regs *regs, u32 cached_flags) > klp_update_patch_state(current); > > /* deal with pending signal delivery */ > - if (cached_flags & _TIF_SIGPENDING) > + if (cached_flags & (_TIF_SIGPENDING | _TIF_RESTORE_SIGMASK)) > do_signal(regs); ... > --- a/kernel/signal.c > +++ b/kernel/signal.c > @@ -2877,6 +2877,7 @@ int set_user_sigmask(const sigset_t __user *usigmask, sigset_t *set, > > *oldset = current->blocked; > set_current_blocked(set); > + set_thread_flag(TIF_RESTORE_SIGMASK); This will re-introduce the problem fixed by the previous patch. Yes, do_signal() does restore_saved_sigmask() at the end, but only if get_signal() returns false. This means that restore_saved_sigmask()->set_current_blocked(saved_mask) should restore ->blocked (and may be clear TIF_SIGPENDING) before ret-from-syscall. Or I misunderstood? Oleg.
