linux-kernel - Re: [PATCH] s390: add support for TIF_NOTIFY

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Date:   Mon, 02 Nov 2020 13:58:00 -0500
From:   Qian Cai <cai@...hat.com>
To:     Jens Axboe <axboe@...nel.dk>
Cc:     linux-s390@...r.kernel.org, Heiko Carstens <hca@...ux.ibm.com>,
        linux-kernel@...r.kernel.org, peterz@...radead.org,
        oleg@...hat.com, tglx@...utronix.de,
        Stephen Rothwell <sfr@...b.auug.org.au>,
        Linux-Next Mailing List <linux-next@...r.kernel.org>
Subject: Re: [PATCH] s390: add support for TIF_NOTIFY_SIGNAL

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: linux-s390@...r.kernel.org
> > > > Signed-off-by: Jens Axboe <axboe@...nel.dk>
> > 
> > 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

> 
> Can you try and add this on top? Looks like I forgot the signal change for
> s390, though that shouldn't really cause any issues.

It does not help with the boot issue at all.

> 
> 
> diff --git a/arch/s390/kernel/signal.c b/arch/s390/kernel/signal.c
> index 9e900a8977bd..a68c3796a1bf 100644
> --- a/arch/s390/kernel/signal.c
> +++ b/arch/s390/kernel/signal.c
> @@ -472,7 +472,7 @@ void do_signal(struct pt_regs *regs)
>  	current->thread.system_call =
>  		test_pt_regs_flag(regs, PIF_SYSCALL) ? regs->int_code : 0;
>  
> -	if (get_signal(&ksig)) {
> +	if (test_thread_flag(TIF_NOTIFY_SIGNAL) && get_signal(&ksig)) {
>  		/* Whee!  Actually deliver the signal.  */
>  		if (current->thread.system_call) {
>  			regs->int_code = current->thread.system_call;
>