Re: [PATCH 3/5] kernel: add support for TIF_NOTIFY_SIGNAL

Oleg Nesterov
2020-10-15T14:37:39Z

On 10/15, Jens Axboe wrote:
>
> On 10/15/20 8:31 AM, Oleg Nesterov wrote:
> > On 10/15, Jens Axboe wrote:
> >>
> >> static inline int signal_pending(struct task_struct *p)
> >> {
> >> +#if defined(CONFIG_GENERIC_ENTRY) && defined(TIF_NOTIFY_SIGNAL)
> >> + /*
> >> + * TIF_NOTIFY_SIGNAL isn't really a signal, but it requires the same
> >> + * behavior in terms of ensuring that we break out of wait loops
> >> + * so that notify signal callbacks can be processed.
> >> + */
> >> + if (unlikely(test_tsk_thread_flag(p, TIF_NOTIFY_SIGNAL)))
> >> + return 1;
> >> +#endif
> >> return task_sigpending(p);
> >> }
> >
> > I don't understand why does this version requires CONFIG_GENERIC_ENTRY.
> >
> > Afaics, it is very easy to change all the non-x86 arches to support
> > TIF_NOTIFY_SIGNAL, but it is not trivial to change them all to use
> > kernel/entry/common.c ?
>
> I think that Thomas wants to gate TIF_NOTIFY_SIGNAL on conversion to
> the generic entry code?

Then I think TIF_NOTIFY_SIGNAL will be never fully supported ;)

Oleg.