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Tue, 10 Mar 2020 14:09:30 +0000 Received: from pps.filterd (userp3020.oracle.com [127.0.0.1]) by userp3020.oracle.com (8.16.0.42/8.16.0.42) with SMTP id 02AE3fKQ085607; Tue, 10 Mar 2020 14:09:30 GMT Received: from userv0122.oracle.com (userv0122.oracle.com [156.151.31.75]) by userp3020.oracle.com with ESMTP id 2yp8rj3676-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 10 Mar 2020 14:09:30 +0000 Received: from abhmp0006.oracle.com (abhmp0006.oracle.com [141.146.116.12]) by userv0122.oracle.com (8.14.4/8.14.4) with ESMTP id 02AE9SZH032502; Tue, 10 Mar 2020 14:09:28 GMT Received: from [192.168.8.5] (/213.41.92.70) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Tue, 10 Mar 2020 07:09:28 -0700 Subject: Re: [patch part-II V2 13/13] x86/entry/common: Split irq tracing in prepare_exit_to_usermode() To: Thomas Gleixner , LKML Cc: x86@kernel.org, Steven Rostedt , Brian Gerst , Juergen Gross , Frederic Weisbecker References: <20200308222359.370649591@linutronix.de> <20200308222610.245444311@linutronix.de> From: Alexandre Chartre Organization: Oracle Corporation Message-ID: Date: Tue, 10 Mar 2020 15:09:31 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.5.0 MIME-Version: 1.0 In-Reply-To: <20200308222610.245444311@linutronix.de> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9555 signatures=668685 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 mlxlogscore=999 phishscore=0 mlxscore=0 spamscore=0 malwarescore=0 bulkscore=0 adultscore=0 suspectscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2001150001 definitions=main-2003100095 X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9555 signatures=668685 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 adultscore=0 lowpriorityscore=0 spamscore=0 priorityscore=1501 impostorscore=0 bulkscore=0 suspectscore=0 phishscore=0 mlxlogscore=999 mlxscore=0 malwarescore=0 clxscore=1015 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2001150001 definitions=main-2003100095 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 3/8/20 11:24 PM, Thomas Gleixner wrote: > As in entry from user mode, lockdep and tracing have different > requirements. lockdep needs to know about the interrupts off state accross > the call to user_enter_irqsoff() but tracing is unsafe after the call. typo: user_enter_irqoff() (no 's' between 'irq' and 'off'). > > Split it up and tell the tracer that interrupts are going to be enabled > before calling user_enter_irqsoff() and tell lockdep afterwards. > > Signed-off-by: Thomas Gleixner > --- > arch/x86/entry/common.c | 12 +++++++++++- > 1 file changed, 11 insertions(+), 1 deletion(-) > > --- a/arch/x86/entry/common.c > +++ b/arch/x86/entry/common.c > @@ -251,9 +251,19 @@ static noinline void __prepare_exit_to_u > { > __prepare_exit_to_usermode(regs); > > + /* > + * Return to user space enables interrupts. Tell the tracer before > + * invoking user_enter_irqsoff() which switches to CONTEXT_USER and Same typo here: user_enter_irqoff() > + * RCU to rcuidle state. Lockdep still needs to keep the irqs > + * disabled state. > + */ > + __trace_hardirqs_on(); > + > user_enter_irqoff(); > mds_user_clear_cpu_buffers(); > - trace_hardirqs_on(); > + > + /* All done. Tell lockdep as well. */ > + lockdep_hardirqs_on(CALLER_ADDR0); > } > NOKPROBE_SYMBOL(prepare_exit_to_usermode); > > Reviewed-by: Alexandre Chartre alex.