From: Oleg Nesterov <oleg@redhat.com>
To: Ingo Molnar <mingo@elte.hu>,
Peter Zijlstra <peterz@infradead.org>,
Srikar Dronamraju <srikar@linux.vnet.ibm.com>,
Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com>,
Anton Arapov <anton@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
Roland McGrath <roland@hack.frob.com>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 4/7] ptrace: Partly fix set_task_blockstep()->update_debugctlmsr() logic
Date: Mon, 10 Sep 2012 19:27:36 +0200 [thread overview]
Message-ID: <20120910172736.GA14168@redhat.com> (raw)
In-Reply-To: <20120903152609.GA9071@redhat.com>
Sebastian, I am replying to my message because I removed your email
by mistake. Fortunately I can see it on marc.info...
> ptrace and uprobe are calling this function from process context. As
> long as you have here get_cpu() instead of local_irq_disable() you should
> be safe here.
local_irq_disable() looks more safe. We can have new users playing
with MSR_IA32_DEBUGCTLMSR from irq.
> perf
> uses raw_local_irqsave() (raw_* most likely due to -RT).
This is completely irrelevant, we alrady discussed this.
> I have no idea
> what you can against NMI unless not touching the register in NMI
> context.
Neither me, and this is documented in the changelog:
And afaics there is yet another problem: perf can play with
MSR_IA32_DEBUGCTLMSR from nmi, this obviously means that even
__switch_to_xtra() has problems.
and please note __switch_to_xtra() above, it has the same problem
by the same reason.
Oleg.
next prev parent reply other threads:[~2012-09-10 17:25 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-09-03 15:25 [PATCH 0/7] uprobes: single-step fixes Oleg Nesterov
2012-09-03 15:25 ` [PATCH 1/7] uprobes: Introduce arch_uprobe_enable/disable_step() Oleg Nesterov
2012-09-07 14:57 ` Srikar Dronamraju
2012-09-03 15:26 ` [PATCH 2/7] uprobes: x86: Implement x86 specific arch_uprobe_*_step Oleg Nesterov
2012-09-07 14:59 ` Srikar Dronamraju
2012-09-03 15:26 ` [PATCH 3/7] ptrace: Introduce set_task_blockstep() helper Oleg Nesterov
2012-09-07 15:00 ` Srikar Dronamraju
2012-09-03 15:26 ` [PATCH 4/7] ptrace: Partly fix set_task_blockstep()->update_debugctlmsr() logic Oleg Nesterov
2012-09-07 15:14 ` Srikar Dronamraju
2012-09-10 16:57 ` Sebastian Andrzej Siewior
2012-09-10 17:45 ` Peter Zijlstra
2012-09-10 17:27 ` Oleg Nesterov [this message]
2012-09-03 15:26 ` [PATCH 5/7] uprobes: Do not (ab)use TIF_SINGLESTEP/user_*_single_step() for single-stepping Oleg Nesterov
2012-09-07 15:11 ` Srikar Dronamraju
2012-09-07 15:50 ` Oleg Nesterov
2012-09-08 7:49 ` Srikar Dronamraju
2012-09-03 15:26 ` [PATCH 6/7] uprobes: Xol should send SIGTRAP if X86_EFLAGS_TF was set Oleg Nesterov
2012-09-12 12:08 ` Srikar Dronamraju
2012-09-12 14:45 ` Oleg Nesterov
2012-09-03 15:26 ` [PATCH 7/7] uprobes: Make arch_uprobe_task->saved_trap_nr "unsigned int" Oleg Nesterov
2012-09-12 12:27 ` Srikar Dronamraju
2012-09-08 17:06 ` [PATCH 0/7] uprobes: single-step fixes Oleg Nesterov
2012-09-12 12:33 ` Srikar Dronamraju
2012-09-08 17:06 ` [PATCH 8/7] uprobes: Fix arch_uprobe_disable_step() && UTASK_SSTEP_TRAPPED interaction Oleg Nesterov
2012-09-12 12:36 ` Srikar Dronamraju
2012-09-10 16:57 ` [PATCH 0/7] uprobes: single-step fixes Sebastian Andrzej Siewior
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