From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
To: Oleg Nesterov <oleg@redhat.com>
Cc: Ingo Molnar <mingo@elte.hu>,
Ananth N Mavinakayanahalli <ananth@in.ibm.com>,
Anton Arapov <anton@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>,
Peter Zijlstra <peterz@infradead.org>,
Roland McGrath <roland@hack.frob.com>,
Srikar Dronamraju <srikar@linux.vnet.ibm.com>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2/2] ptrace: fix set_task_blockstep()->update_debugctlmsr() logic
Date: Tue, 07 Aug 2012 11:41:56 +0200 [thread overview]
Message-ID: <5020E2E4.3090104@linutronix.de> (raw)
In-Reply-To: <20120803162954.GA19806@redhat.com>
On 08/03/2012 06:29 PM, Oleg Nesterov wrote:
> --- a/arch/x86/kernel/step.c
> +++ b/arch/x86/kernel/step.c
> @@ -166,12 +166,18 @@ static void set_task_blockstep(struct task_struct *task, bool on)
> else
> clear_tsk_thread_flag(task, TIF_BLOCKSTEP);
>
> + if (task != current)
> + return;
> +
> + /* ensure irq/preemption can't change debugctl in between */
> + local_irq_disable();
> debugctl = get_debugctlmsr();
> if (on)
> debugctl |= DEBUGCTLMSR_BTF;
> else
> debugctl&= ~DEBUGCTLMSR_BTF;
> update_debugctlmsr(debugctl);
> + local_irq_enable();
> }
I would say that you can remove this chunk. For task != current we
leave.
For uprobes we never set the bit, we only need it cleared. We get here
via int 3 and do_debug() already clears TIF_BLOCKSTEP because the
CPU clears the bit in CPU. So both, TIF_BLOCKSTEP and DEBUGCTLMSR_BTF
are never set.
Sebastian
next prev parent reply other threads:[~2012-08-07 9:42 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-08-03 16:29 [PATCH 0/2] ptrace: DEBUGCTLMSR_BTF fixes Oleg Nesterov
2012-08-03 16:29 ` [PATCH 1/2] ptrace: introduce set_task_blockstep() helper Oleg Nesterov
2012-08-03 16:29 ` [PATCH 2/2] ptrace: fix set_task_blockstep()->update_debugctlmsr() logic Oleg Nesterov
2012-08-03 16:43 ` Sebastian Andrzej Siewior
2012-08-03 17:38 ` Oleg Nesterov
2012-08-03 18:28 ` Sebastian Andrzej Siewior
2012-08-07 15:13 ` Oleg Nesterov
2012-08-07 9:41 ` Sebastian Andrzej Siewior [this message]
2012-08-07 10:52 ` Sebastian Andrzej Siewior
2012-08-07 15:15 ` Oleg Nesterov
2012-08-07 15:29 ` Sebastian Andrzej Siewior
2012-08-07 15:31 ` Oleg Nesterov
2012-08-07 15:12 ` Oleg Nesterov
2012-08-06 16:14 ` [PATCH 0/2] ptrace: DEBUGCTLMSR_BTF fixes Sebastian Andrzej Siewior
2012-08-07 15:15 ` Oleg Nesterov
2012-08-07 15:38 ` Sebastian Andrzej Siewior
2012-08-07 15:46 ` Oleg Nesterov
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