linux-kernel - Re: [RFC PATCH] set TASK_TRACED before arch

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Date:	Thu, 22 May 2008 21:24:11 +0800
From:	"Luming Yu" <luming.yu@...il.com>
To:	"Roland McGrath" <roland@...hat.com>
Cc:	"Petr Tesarik" <ptesarik@...e.cz>,
	LKML <linux-kernel@...r.kernel.org>, linux-ia64@...r.kernel.org
Subject: Re: [RFC PATCH] set TASK_TRACED before arch_ptrace code to fix a race

On Thu, May 22, 2008 at 7:18 PM, Roland McGrath <roland@...hat.com> wrote:
> I really cannot figure out from anything you've said what the failure mode
> is or how you think it should be affected.

Sorry for confusion, Let me try to explain it more:

For ia64,the code path is like:
ptrace_notify (to let the debugger run)--> ptrace_stop
-->spin_unlock_irq->arch_ptrace_stop (ia64_ptrace_stop) ->[sync rbs
and set NOTIFY_RESUME.....]-->spin_lock_irq->set TASK_TRACED flag (to
let the debugger run)

For x86, the code path is like:
ptrace_notify (to let the debugger run) ->ptrace_stop->set TASK_TRACED
flag (to let the debugger run)-->spin_unlock_irq

If TASK_TRACED is not set earlier before arch_ptrace_stop on ia64
ptrace_notify code path, some signals would be delivered without
letting debugger run.. (i.e. PTRACED logica in get_signal_to_deliver
would be ignored totally!). These should cause the test case hang on
ia64. And x86 just works..

If you have any question , I would dig further..

Thanks,
Luming
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