| Date | Wed, 13 May 2020 16:56:41 -0400 (EDT) | From | Mathieu Desnoyers <> | Subject | Re: [patch V4 part 1 05/36] x86/entry: Flip _TIF_SIGPENDING and _TIF_NOTIFY_RESUME handling |
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----- On May 5, 2020, at 9:16 AM, Thomas Gleixner tglx@linutronix.de wrote:
> Make sure task_work runs before any kind of userspace -- very much > including signals -- is invoked.
What is missing from this patch description is: _why_ is this deemed useful ?
Also, color me confused: is "do_signal()" actually running any user-space, or just setting up the user-space stack for eventual return to signal handler ?
Also, it might be OK, but we're changing the order of two things which have effects on each other: restartable sequences abort fixup for preemption and do_signal(), which also have effects on rseq abort.
Because those two will cause the abort to trigger, I suspect changing the order might be OK, but we really need to think this through.
Thanks,
Mathieu
> > Suggested-by: Andy Lutomirski <luto@kernel.org> > Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> > Signed-off-by: Thomas Gleixner <tglx@linutronix.de> > --- > arch/x86/entry/common.c | 8 ++++---- > 1 file changed, 4 insertions(+), 4 deletions(-) > > --- a/arch/x86/entry/common.c > +++ b/arch/x86/entry/common.c > @@ -156,16 +156,16 @@ static void exit_to_usermode_loop(struct > if (cached_flags & _TIF_PATCH_PENDING) > klp_update_patch_state(current); > > - /* deal with pending signal delivery */ > - if (cached_flags & _TIF_SIGPENDING) > - do_signal(regs); > - > if (cached_flags & _TIF_NOTIFY_RESUME) { > clear_thread_flag(TIF_NOTIFY_RESUME); > tracehook_notify_resume(regs); > rseq_handle_notify_resume(NULL, regs); > } > > + /* deal with pending signal delivery */ > + if (cached_flags & _TIF_SIGPENDING) > + do_signal(regs); > + > if (cached_flags & _TIF_USER_RETURN_NOTIFY) > fire_user_return_notifiers();
-- Mathieu Desnoyers EfficiOS Inc. http://www.efficios.com
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