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Date: Tue, 08 Aug 2006 15:25:04 -0700 (PDT)
Message-Id: <20060808.152504.55835990.davem@davemloft.net>
Subject: Re: Signal restarting happing multiple time in do_signal
From: David Miller <davem@davemloft.net>
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From: Ralf Baechle <ralf@linux-mips.org>
Date: Tue, 8 Aug 2006 12:04:37 +0100

> We were able to trigger this when debugging a multithreaded programs.
> At least i386 uses virtually identical algorithms so I think is likely
> to have the same issue.

Other platforms, including x86, clear the state out in one way or
another before the next iteration.

Actually on x86 it occurs as a side effect of setting
regs->eax, it is reset to the system call number requested
at syscall trap time, so it will not match any of the
error return values in this switch statement:

	/* Are we from a system call? */
	if (regs->orig_eax >= 0) {
		/* If so, check system call restarting.. */
		switch (regs->eax) {
		        case -ERESTART_RESTARTBLOCK:
			case -ERESTARTNOHAND:
				regs->eax = -EINTR;
				break;

			case -ERESTARTSYS:
				if (!(ka->sa.sa_flags & SA_RESTART)) {
					regs->eax = -EINTR;
					break;
				}
			/* fallthrough */
			case -ERESTARTNOINTR:
				regs->eax = regs->orig_eax;
				regs->eip -= 2;
		}
	}

So after the first iteration, the next time through here we
won't be "from a system call".