Date:   Fri, 17 Feb 2023 20:04:37 +0100
From:   luca abeni <luca.abeni@santannapisa.it>
To:     Daniel Bristot de Oliveira <bristot@redhat.com>
Cc:     Wander Lairson Costa <wander@redhat.com>,
        Valentin Schneider <vschneid@redhat.com>,
        Oleg Nesterov <oleg@redhat.com>,
        Ingo Molnar <mingo@redhat.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Juri Lelli <juri.lelli@redhat.com>,
        Vincent Guittot <vincent.guittot@linaro.org>,
        Dietmar Eggemann <dietmar.eggemann@arm.com>,
        Steven Rostedt <rostedt@goodmis.org>,
        Ben Segall <bsegall@google.com>, Mel Gorman <mgorman@suse.de>,
        "Eric W. Biederman" <ebiederm@xmission.com>,
        Stafford Horne <shorne@gmail.com>,
        Kefeng Wang <wangkefeng.wang@huawei.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
        Andy Lutomirski <luto@kernel.org>,
        "Liam R. Howlett" <Liam.Howlett@oracle.com>,
        Fenghua Yu <fenghua.yu@intel.com>,
        Andrei Vagin <avagin@gmail.com>,
        open list <linux-kernel@vger.kernel.org>,
        Paul McKenney <paulmck@kernel.org>
Subject: Re: [PATCH v2 1/4] sched/task: Add the put_task_struct_atomic_safe
 function
Message-ID: <20230217200437.551ad7c2@nowhere>
In-Reply-To: <8632d9c6-7ec7-c3aa-f9e7-fa63cc82f6ae@redhat.com>
References: <20230120150246.20797-1-wander@redhat.com>
        <20230120150246.20797-2-wander@redhat.com>
        <20230123163002.GB6268@redhat.com>
        <CAAq0SUk1vfNDuzGbXNftgW4wq4PC_EzMhpq4E=RBQNkOB3f4YQ@mail.gmail.com>
        <xhsmhbkmkdla4.mognet@vschneid.remote.csb>
        <CAAq0SUnUH6DEjwEs2RxRCtkTU121JXpdsV_rZky1d0Bo04=fiQ@mail.gmail.com>
        <8632d9c6-7ec7-c3aa-f9e7-fa63cc82f6ae@redhat.com>
Organization: Scuola Superiore Sant'Anna
Content-Type: text/plain; charset=US-ASCII
Content-Transfer-Encoding: 7bit
MIME-Version: 1.0
X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1
X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?kpj0u41yQ5eY+210C3lWk+6+G+GY5cfQiQbV+0lBdP/qXiL38q5ogGaRXEvS?=
 =?us-ascii?Q?q7ARDw84q8J16WSD5mUG5IhIuoctpqLGhokt5oSsPRWlruhhdob9YJZOkAjy?=
 =?us-ascii?Q?A0UxcVBwHpmdKbqse1pGyeJYgt+LWVi6Xyoq/AkzBs/ni3p7htoiflp2kc5l?=
 =?us-ascii?Q?eS6TVCg+0BCo1x8uBM40T5Q+r+bCyL7YTRXMLb60sc2M6M1Dn46c2Tntl6yU?=
 =?us-ascii?Q?1vEPW97xADv41nz1mfX6zTW9qOvxwivJAm4Dsl3JbSwJP7s7enqiFMT3c0IS?=
 =?us-ascii?Q?c3wwfYFQYpiCFOmuQwVlk9ReUVmVtKRFbgH8NlaStTuAf/vNjVha0oAdWy4G?=
 =?us-ascii?Q?e/51pvBqhvc2dhf3OJNS7KIml4wPIKbW0SiqMTzrtH89MHaONaRPDw7bZ/Ib?=
 =?us-ascii?Q?5VvfZegGsnRO+3Uh/DS474RXAO+D78gNRvUJqpDWHo2rxSw0VWCSVB6tZRED?=
 =?us-ascii?Q?qiZFULPBbPnxwWY9zlwki808+Sb6P2/xkQatraHLxNOQ4/oOG0E35vOiyAXv?=
 =?us-ascii?Q?c4w+WzuM/URdLmgzCfSNzkJUP88fZqz2ZADVG1YXUT0Sr7lZRl84lGj74ZHi?=
 =?us-ascii?Q?KVCdrrF3h05zKqcmLrD/MzgP6rrXejdNxLBziqcbO8EI5zO3DGw8ILzTIVCb?=
 =?us-ascii?Q?90Z9PUM5i1o7DBGDgCe++GlRnXyT+kdrnU70VGjPmgOgGEV4CxFynQDmybbU?=
 =?us-ascii?Q?m/weEoBSVH7SJFmH/gwXkmQ3X96BPJHw6/YKz+wZoWs8wxyT4jk1WWrjFPPY?=
 =?us-ascii?Q?PWuyOrR+NeIp59OsyVSTY5Q6LaKX+xtlkLYpXdBfIdGDyRn6pY/ItDQ3Cs1U?=
 =?us-ascii?Q?w/8x0ahB8V3jlXL3PqyUlyV0LutjZBzAfXZHMxLylSZWCyx4O1PnVW2E3qOE?=
 =?us-ascii?Q?NA/RVjj1ewNgmJG9DchCIeh+x8UhIVeQ4GUOatzi0/03r3TuQ/dJFiAqNitO?=
 =?us-ascii?Q?FcZjZW3pwNLKF4BgrMvLD4jIIL1rmM14Au00CnaG0yXv/tTg2rfQWuBdv4y8?=
 =?us-ascii?Q?J/W0Lbbb1nE1I1LAj6+8JnGL38ZjU+2Mnk9iyBbaJ9x+GrmyQKvV4f+xc+qV?=
 =?us-ascii?Q?+3UxfCHiZOFYecUzb6VW7ofi//pend4Dpcy57BcQj2IwFLaW+SSlFsXIPMRk?=
 =?us-ascii?Q?DqRn68HMhri0/hskfmt4R1o+9ijalI4ZxNqOX4oSX2DOOcoRjRq8EEqiMMBp?=
 =?us-ascii?Q?FsR+Ta8X2lnz3EkkbQlLedsf8FoX8cYNwzYqC0joQj2OD7vpoJ7AXJqj2C/v?=
 =?us-ascii?Q?dveDWRLyzSGsLUCoL8su8tEJfGN3OWuXqpCfEo5/J5kEcM7KYda5U0UY4cdV?=
 =?us-ascii?Q?ntD9Gevx7YEzbhTj9tRhP6C5TSra/m9o/RC6E6S2t2mk3Uyo4pd0VGe9yy7J?=
 =?us-ascii?Q?EHYScenq89F6e/CQiC6kURvdfFfrRe92MhZQ0297auUM9e5bEHWsDvNwhtTf?=
 =?us-ascii?Q?kUxNE4zUH47ZO4LRRzwtIW1xH+5ct/9gjyLy5dZTcnPawzpUyVf8nRp/h5L5?=
 =?us-ascii?Q?mqxIgvOBVomzzcr2B8l5qZrKpA/XWTCxVVwNftBCathwUFIR+OxS4k0RZXHK?=
 =?us-ascii?Q?Ci4e7qwTzsrb4z0iUv2Sx259e+JE2t7nrtgipTFrIZwyJGfN/Y9kRxOsr32H?=
 =?us-ascii?Q?2g=3D=3D?=
X-OriginatorOrg: santannapisa.it
X-MS-Exchange-CrossTenant-Network-Message-Id: 0313ba81-10bb-4458-03c5-08db1119d42b
X-MS-Exchange-CrossTenant-AuthSource: AM5PR03MB2867.eurprd03.prod.outlook.com
X-MS-Exchange-CrossTenant-AuthAs: Internal
X-MS-Exchange-CrossTenant-OriginalArrivalTime: 17 Feb 2023 19:04:43.6062
 (UTC)
X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted
X-MS-Exchange-CrossTenant-Id: d97360e3-138d-4b5f-956f-a646c364a01e
X-MS-Exchange-CrossTenant-MailboxType: HOSTED
X-MS-Exchange-CrossTenant-UserPrincipalName: 8P9Bb0fbfkevTVotojzwU5rXIl7QNWf/jZnzJ5dAsNBqHGggeims/D0cOnzXvPD1QJpMfx9Yd6h26a2HgQwbc4FTihC+uo+RP2Z9SW9hq2Y=
X-MS-Exchange-Transport-CrossTenantHeadersStamped: PR3PR03MB6633
Precedence: bulk
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

Hi all,

On Fri, 17 Feb 2023 14:35:22 -0300
Daniel Bristot de Oliveira <bristot@redhat.com> wrote:

> On 1/30/23 08:49, Wander Lairson Costa wrote:
> >> Another thing, if you look at release_task_stack(), it either
> >> caches the outgoing stack for later use, or frees it via RCU
> >> (regardless of PREEMPT_RT). Perhaps we could follow that and just
> >> always punt the freeing of the task struct to RCU?
> >>  
> > That's a point. Do you mean doing that even for !PREEMPT_RT?
> >   
> 
> It seems that Luca Abeni (in Cc) is hitting the bug in the non-rt
> kernel with SCHED_DEADLINE...
> 
> adding him to the thread.

Thanks Daniel for adding me.

I triggered this "BUG: Invalid wait context" with a 5.15.76 kernel,
without PREEMPT_RT. I can reproduce it easily on a KVM-based VM; if
more information or tests are needed, let me know.


			Luca