RE: [PATCH -mm 0/1] signal: simplify set_user_sigmask/restore_user_sigmask

[David Laight]

From: Linus Torvalds
> Sent: 05 June 2019 18:25
> 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".
> 
> Which would be fairly easy to do with something like the attached...

That would always call the signal handlers even when EINTR wasn't
being returned (which I think ought to happen ...).
The real purpose of restore_saved_sigmask() is to stop signal
handlers that are enabled by the temporary mask being called.

If a signal handler is called, I presume that the trampoline
calls back into the kernel to get further handlers called
and to finally restore the original signal mask?

What happens if a signal handler calls something that
would normally write to current->saved_sigmask?

	David

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