linux-kernel - Re: [PATCH RT 2/2 v4] preempt-rt/x86: Delay calling signals in int3

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Date:	Fri, 3 Feb 2012 19:40:16 +0100
From:	Oleg Nesterov <oleg@...hat.com>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	linux-kernel@...r.kernel.org,
	linux-rt-users <linux-rt-users@...r.kernel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Carsten Emde <C.Emde@...dl.org>,
	John Kacur <jkacur@...hat.com>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	Ingo Molnar <mingo@...e.hu>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"H. Peter Anvin" <hpa@...or.com>,
	Alexander van Heukelum <heukelum@...tmail.fm>,
	Andi Kleen <ak@...ux.intel.com>,
	Clark Williams <williams@...hat.com>,
	Luis Goncalves <lgoncalv@...hat.com>, stable-rt@...r.kernel.org
Subject: Re: [PATCH RT 2/2 v4] preempt-rt/x86: Delay calling signals in int3

Steven, I guess I need to actually read the patch before asking the
questions... I'll try later, but

On 02/03, Steven Rostedt wrote:
>
> --- linux-rt.git.orig/arch/x86/kernel/entry_64.S
> +++ linux-rt.git/arch/x86/kernel/entry_64.S
> @@ -1391,6 +1391,14 @@ paranoid_userspace:
>  paranoid_schedule:
>  	TRACE_IRQS_ON
>  	ENABLE_INTERRUPTS(CLBR_ANY)
> +#ifdef CONFIG_PREEMPT_RT_FULL
> +	GET_THREAD_INFO(%rcx)
> +	movl TI_flags(%rcx),%ebx
> +	testl $_TIF_FORCE_SIG_TRAP,%ebx
> +	jz paranoid_do_schedule
> +	call do_force_sig_trap
> +paranoid_do_schedule:
> +#endif

Stupid question. Do we really need to send the signal from here?

Why force_sig(rt => T) can't set TIF_NOTIFY_RESUME instead? Then
we can change do_notify_resume() to check TIF_FORCE_SIG_TRAP. And
perhaps we can even avoid the new TIF_FORCE_SIG_TRAP, we could
check task->stored_info_set.

In fact I feel this can be simplified even more, but I am not sure.

Oleg.

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