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Date: Thu, 31 Jul 2014 20:50:29 +0200
Message-ID: <CAFTL4hyHh3Bw0eeJe9q50HVrt=B-zgmyu6C_hy+RoW21kQEJtg@mail.gmail.com>
Subject: Re: TIF_NOHZ can escape nonhz mask? (Was: [PATCH v3 6/8] x86: Split
 syscall_trace_enter into two phases)
From: Frederic Weisbecker <fweisbec@gmail.com>
To: Oleg Nesterov <oleg@redhat.com>
Cc: Andy Lutomirski <luto@amacapital.net>,
        "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
        LKML <linux-kernel@vger.kernel.org>, Kees Cook <keescook@chromium.org>,
        Will Drewry <wad@chromium.org>,
        "the arch/x86 maintainers" <x86@kernel.org>,
        "<linux-arm-kernel@lists.infradead.org>" 
	<linux-arm-kernel@lists.infradead.org>,
        Linux MIPS Mailing List <linux-mips@linux-mips.org>,
        "linux-arch@vger.kernel.org" <linux-arch@vger.kernel.org>,
        LSM List <linux-security-module@vger.kernel.org>,
        Alexei Starovoitov <ast@plumgrid.com>,
        "H. Peter Anvin" <hpa@zytor.com>
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Sender: linux-kernel-owner@vger.kernel.org

2014-07-31 20:47 GMT+02:00 Frederic Weisbecker <fweisbec@gmail.com>:
> On Thu, Jul 31, 2014 at 08:12:30PM +0200, Oleg Nesterov wrote:
>> On 07/31, Frederic Weisbecker wrote:
> No, because preempt_schedule_irq() does the ctx_state save and restore with
> exception_enter/exception_exit.

Similar thing happens with schedule_user().

preempt_schedule_irq() handles kernel preemption and schedule_user()
the user preemption. On both cases we save and restore the context
tracking state.

This might be the missing piece you were missing :)
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