On 06/05, Linus Torvalds wrote:
On Wed, Jun 5, 2019 at 8:58 AM Oleg Nesterov oleg@redhat.com 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.