linux-kernel - Re: [RFC] TIF_NOTIFY_RESUME, arch/*/*/*signal*.c and all such

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Date:	Wed, 25 Apr 2012 17:46:11 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Al Viro <viro@...IV.linux.org.uk>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	linux-arch@...r.kernel.org, linux-kernel@...r.kernel.org,
	Russell King <linux@....linux.org.uk>,
	Tejun Heo <tj@...nel.org>, Arnd Bergmann <arnd@...db.de>,
	Roland McGrath <roland@...k.frob.com>
Subject: Re: [RFC] TIF_NOTIFY_RESUME, arch/*/*/*signal*.c and all such

On 04/25, Oleg Nesterov wrote:
>
> On 04/25, Al Viro wrote:
> >
> > Point...  Still, since we are talking about an arbitrary wide window (the
> > damn thing is waiting for signals to arrive, after all) this doesn't
> > sound good;
> > ...
> > IMO it's
> > a QoI problem at the very least.
>
> and looks confusing, agreed.

OK, I didn't really try to think, and somehow I simply can't wake up today.
But perhaps we can do something the following? We add the new syscall

	sys_eintr(void)
	{
		return -EINTR;
	}

(perhaps not strictly needed, perhaps we can reuse sys_restart_syscal)

Now,

	--- x/arch/x86/kernel/signal.c
	+++ x/arch/x86/kernel/signal.c
	@@ -711,6 +711,13 @@ handle_signal(unsigned long sig, siginfo
				regs->ax = regs->orig_ax;
				regs->ip -= 2;
				break;
	+
	+		case -EINTR:
	+			break;
	+
	+		default:
	+			if (regs->orig_ax == NR_eintr)
	+				regs->ax = NR_eintr;
			}
		}
	 
	@@ -791,6 +798,7 @@ static void do_signal(struct pt_regs *re
			case -ERESTARTSYS:
			case -ERESTARTNOINTR:
				regs->ax = regs->orig_ax;
	+			regs->orig_ax = NR_eintr;
				regs->ip -= 2;
				break;
	 

this ignores ERESTART_RESTARTBLOCK for simplicity.

And I am not sure this can't confuse the tools like strace...

Oleg.

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