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From: Oleg Nesterov <[email protected]>
To: Jens Axboe <[email protected]>
Cc: [email protected], [email protected],
	[email protected], [email protected]
Subject: Re: [PATCH 4/6] kernel: add support for TIF_NOTIFY_SIGNAL
Date: Thu, 8 Oct 2020 15:53:26 +0200	[thread overview]
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>

On 10/05, Jens Axboe wrote:
>
>  static inline int signal_pending(struct task_struct *p)
>  {
> +#ifdef 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);
>  }

perhaps we can add test_tsk_thread_mask() later...

>  static inline void restore_saved_sigmask_unless(bool interrupted)
>  {
> -	if (interrupted)
> +	if (interrupted) {
> +#ifdef TIF_NOTIFY_SIGNAL
> +		WARN_ON(!test_thread_flag(TIF_SIGPENDING) &&
> +			!test_thread_flag(TIF_NOTIFY_SIGNAL));
> +#else
>  		WARN_ON(!test_thread_flag(TIF_SIGPENDING));
> -	else
> +#endif
> +	} else {
>  		restore_saved_sigmask();
> +	}

I'd suggest to simply do

	-	WARN_ON(!test_thread_flag(TIF_SIGPENDING));
	+	WARN_ON(!signal_pending(current);


> --- a/kernel/entry/kvm.c
> +++ b/kernel/entry/kvm.c
> @@ -8,6 +8,9 @@ static int xfer_to_guest_mode_work(struct kvm_vcpu *vcpu, unsigned long ti_work)
>  	do {
>  		int ret;
>  
> +		if (ti_work & _TIF_NOTIFY_SIGNAL)
> +			tracehook_notify_signal();

Can't really comment this change, but to me it would be more safe to
simply return -EINTR.

Or perhaps even better, treat _TIF_NOTIFY_SIGNAL and _TIF_SIGPENDING
equally:

	-	if (ti_work & _TIF_SIGPENDING) {
	+	if (ti_work & (_TIF_SIGPENDING | _TIF_NOTIFY_SIGNAL)) {
			kvm_handle_signal_exit(vcpu);
			return -EINTR;

Oleg.


  reply	other threads:[~2020-10-08 13:53 UTC|newest]

Thread overview: 30+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-10-05 15:04 [PATCHSET RFC v3 0/6] Add support for TIF_NOTIFY_SIGNAL Jens Axboe
2020-10-05 15:04 ` [PATCH 1/6] tracehook: clear TIF_NOTIFY_RESUME in tracehook_notify_resume() Jens Axboe
2020-10-08 12:37   ` Oleg Nesterov
2020-10-08 13:36     ` Jens Axboe
2020-10-05 15:04 ` [PATCH 2/6] kernel: add task_sigpending() helper Jens Axboe
2020-10-08 12:58   ` Oleg Nesterov
2020-10-08 13:36     ` Jens Axboe
2020-10-08 13:24   ` Oleg Nesterov
2020-10-08 13:38     ` Jens Axboe
2020-10-05 15:04 ` [PATCH 3/6] kernel: split syscall restart from signal handling Jens Axboe
2020-10-08 14:21   ` Oleg Nesterov
2020-10-08 14:31     ` Jens Axboe
2020-10-08 14:41       ` Jens Axboe
2020-10-08 14:45       ` Oleg Nesterov
2020-10-08 14:47         ` Jens Axboe
2020-10-05 15:04 ` [PATCH 4/6] kernel: add support for TIF_NOTIFY_SIGNAL Jens Axboe
2020-10-08 13:53   ` Oleg Nesterov [this message]
2020-10-08 14:07     ` Jens Axboe
2020-10-08 14:27       ` Oleg Nesterov
2020-10-05 15:04 ` [PATCH 5/6] x86: define _TIF_NOTIFY_SIGNAL Jens Axboe
2020-10-05 15:04 ` [PATCH 6/6] task_work: use TIF_NOTIFY_SIGNAL if available Jens Axboe
2020-10-08 14:56 ` [PATCHSET RFC v3 0/6] Add support for TIF_NOTIFY_SIGNAL Oleg Nesterov
2020-10-08 15:00   ` Jens Axboe
2020-10-09  8:01   ` Miroslav Benes
2020-10-09 15:21     ` Jens Axboe
2020-10-10 16:53       ` Jens Axboe
2020-10-12 17:27         ` Miroslav Benes
2020-10-13 19:39           ` Jens Axboe
2020-10-13 23:34             ` Thomas Gleixner
2020-10-13 23:37               ` Jens Axboe

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