Subject: Re: [PATCH] s390: add support for TIF_NOTIFY_SIGNAL

From: Jens Axboe <[email-masked]>
Date: Mon, 2 Nov 2020 12:50:07 -0700

On 11/2/20 11:58 AM, Qian Cai wrote:
> On Mon, 2020-11-02 at 10:07 -0700, Jens Axboe wrote:
>> On 11/2/20 9:59 AM, Qian Cai wrote:
>>> On Sun, 2020-11-01 at 17:31 +0000, Heiko Carstens wrote:
>>>> On Thu, Oct 29, 2020 at 10:21:11AM -0600, Jens Axboe wrote:
>>>>> Wire up TIF_NOTIFY_SIGNAL handling for s390.
>>>>>
>>>>> Cc: [email-masked]
>>>>> Signed-off-by: Jens Axboe <[email-masked]>
>>>
>>> Even though I did confirm that today's linux-next contains this additional
>>> patch
>>> from Heiko below, a z10 guest is still unable to boot. Reverting the whole
>>> series (reverting only "s390: add support for TIF_NOTIFY_SIGNAL" introduced
>>> compiling errors) fixed the problem, i.e., git revert --no-edit
>>> af0dd809f3d3..7b074c15374c [1]
>>
>> That's odd, it should build fine without that patch. How did it fail for you?
> 
> In file included from ./arch/s390/include/asm/bug.h:5,
>                  from ./include/linux/bug.h:5,
>                  from ./include/linux/mmdebug.h:5,
>                  from ./include/linux/percpu.h:5,
>                  from ./include/linux/context_tracking_state.h:5,
>                  from ./include/linux/hardirq.h:5,
>                  from ./include/linux/kvm_host.h:7,
>                  from arch/s390/kernel/asm-offsets.c:11:
> ./include/linux/sched/signal.h: In function ‘signal_pending’:
> ./include/linux/sched/signal.h:368:39: error: ‘TIF_NOTIFY_SIGNAL’ undeclared
> (first use in this function); did you mean ‘TIF_NOTIFY_RESUME’?
>   if (unlikely(test_tsk_thread_flag(p, TIF_NOTIFY_SIGNAL)))
>                                        ^~~~~~~~~~~~~~~~~
> ./include/linux/compiler.h:78:42: note: in definition of macro ‘unlikely’
>  # define unlikely(x) __builtin_expect(!!(x), 0)
>                                           ^
> ./include/linux/sched/signal.h:368:39: note: each undeclared identifier is
> reported only once for each function it appears in
>   if (unlikely(test_tsk_thread_flag(p, TIF_NOTIFY_SIGNAL)))
>                                        ^~~~~~~~~~~~~~~~~
> ./include/linux/compiler.h:78:42: note: in definition of macro ‘unlikely’
>  # define unlikely(x) __builtin_expect(!!(x), 0)
>                                           ^
> make[1]: *** [scripts/Makefile.build:117: arch/s390/kernel/asm-offsets.s] Error
> 1
> make: *** [Makefile:1198: prepare0] Error 2

Ah, but that's because later patches assume that TIF_NOTIFY_SIGNAL is
always there once all archs have been converted. If you just want to back
out that patch, you'll need to just revert this one:

commit 82ef6998ed9d488e56bbfbcc2ec9adf62bf78f08
Author: Jens Axboe <[email-masked]>
Date:   Fri Oct 9 16:04:39 2020 -0600

    kernel: remove checking for TIF_NOTIFY_SIGNAL

as well and I suspect it should build.

-- 
Jens Axboe