Received-SPF: pass (google.com: domain of linux-kernel+bounces-151119-linux.lists.archive=gmail.com@vger.kernel.org designates 147.75.199.223 as permitted sender) client-ip=147.75.199.223;
Message-ID: <5febb249-1d4d-4ea7-b031-1df4d14620d2@oracle.com>
Date: Fri, 19 Apr 2024 13:09:09 +0530
User-Agent: Mozilla Thunderbird
Subject: Re: [bug-report] task info hung problem in fb_deferred_io_work()
To: Takashi Iwai <tiwai@suse.de>, Helge Deller <deller@gmx.de>
Cc: Nam Cao <namcao@linutronix.de>, Thomas Zimmermann <tzimmermann@suse.de>,
        Daniel Vetter <daniel@ffwll.ch>, linux-fbdev@vger.kernel.org,
        dri-devel@lists.freedesktop.org, bigeasy@linutronix.de,
        patrik.r.jakobsson@gmail.com, LKML <linux-kernel@vger.kernel.org>,
        Vegard Nossum <vegard.nossum@oracle.com>,
        George Kennedy <george.kennedy@oracle.com>,
        Darren Kenny <darren.kenny@oracle.com>, chuansheng.liu@intel.com
References: <271372d6-e665-4e7f-b088-dee5f4ab341a@oracle.com>
 <20240418160652.68df1a86@namcao> <87ttjywxv5.wl-tiwai@suse.de>
 <a7843657-c3f6-4d2e-8c36-5541d4c52956@gmx.de> <878r19voks.wl-tiwai@suse.de>
Content-Language: en-US
From: Harshit Mogalapalli <harshit.m.mogalapalli@oracle.com>
In-Reply-To: <878r19voks.wl-tiwai@suse.de>
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 7bit
Precedence: bulk
MIME-Version: 1.0
X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1
X-MS-Exchange-AntiSpam-MessageData-0: 
	=?utf-8?B?ekVVNU5EaUlRekJ1QUZySTl3QVdvYmZ0dkNHL1hDWGpMNWpsNkdISnhRcjFG?=
 =?utf-8?B?VmJVZkFrR1ZCR3JkUmNZLzM4aWRVelYxNVlBek9SZkM3Y0dlL3NYSyt1ei9u?=
 =?utf-8?B?azkyNk5xaERqN3ZjNTh1aVd2c0tQaGVDQ0F1SENHSjh4VjV5OGlUaWxYc29M?=
 =?utf-8?B?Z1FYK0FrYTV2ZG5ZWXJxU0hab0NBZm5uaEU4dUJULzc4QTltK3BUS2NpbjFs?=
 =?utf-8?B?U05vcWFxQ2M3SFNyalIzdWFpY1M0R1NTVWk1Wi9nT3NneFdHMEdGellQTExR?=
 =?utf-8?B?MnpNbnNzOE9RaHc4S0p0dzJLWVFNRG00WVgyaWRxSWRxM0dsSU55U1Z4RHZC?=
 =?utf-8?B?ZEE5ZExOMHBQWWZpMEtaMnhtRFBpVnNzcUVCeUVNMkZkekRkc0dvM3BkL2Vw?=
 =?utf-8?B?eHQzT0VOMXhMZnBFNHg3NU1kSzZNd1p6TnVMT0pZdnFuNzlxVHZGbzN1aGVV?=
 =?utf-8?B?aXhrTER2ZmRXZ2gramhRUGdvdFRlMWxVdjRmWFpDakVtaE9zUmlPaXVJbWhX?=
 =?utf-8?B?V3d2NEk3UDVTQ2ZKTitrb1hJL0dvejFMUVphcndZajR5OEpPVmJZem16Tmtq?=
 =?utf-8?B?MWdpVmZXbVB2ODNnZVlJNEJCRDhSR2I0cUQyRUlrLzFLL0pCU1BySEZraHEz?=
 =?utf-8?B?L0xwRDJZbUk4YS9sNmV2RnZpSG8vWDFZMlR5bGplYnE2V3J1ZWhoYXVKTFpB?=
 =?utf-8?B?MkpmWk85THlLczZGaGMwSDJEVXVUTnBVM2ZuVDBVa056NU1Sa3JYcTdHSXdh?=
 =?utf-8?B?M3grV3RkaWswT0Nmd1dlKzF2Q0U3aXRWTUxjUUxUUFMyVkJCNjh3NVY5cmx0?=
 =?utf-8?B?Z1UvZVNuSGRMSmdMUmhNRUozTFdiVjlLcnJ5RjVxdTBPRkIwL2VFZGQ1cjJz?=
 =?utf-8?B?UUlaekdGREtqaUpZSDhxbHFUVXBDVmJOaldnUjZsYlVXdkNnMjJLd2dXME1m?=
 =?utf-8?B?QjhpeXgzRW15eDcyN252L3FZTlJuYjBaajlCY3NCNjVSRXFRVEFuZnlrblow?=
 =?utf-8?B?UGFZaHdYejh2YWZFMThZV3JBR3RzaXRjOWNtWUt2YUsyVUk5YzFuakhFaHBN?=
 =?utf-8?B?MndtUTZpRi9MUVp6NEpmRkpqZ0lqOWtzVkZYdVBMSSs0a3Nzd1JiamJ2amdj?=
 =?utf-8?B?MzdOem1ZeGl5a0tON0g0TFowd3kyWXh0UTJhN2xiZHJ6U3RYcGZEd3ZWKzBi?=
 =?utf-8?B?ZXovMi9kbjUwY0VBSlFWUTJhRjArMkE0bkpVUEp4SlhjL2pMcmxJZFBCZVZp?=
 =?utf-8?B?K3VBYXMwSmNUUFY5ZkwyUTVLZ09PNWZ1aGdCdDI1UVpoODh0d0ZOdnVOWFQr?=
 =?utf-8?B?RkdVQ0pmUk52TGxFc1ZtVTRlNnlyTlNOckZtaEpSbjVsc09ETDNETnYydHEw?=
 =?utf-8?B?VjRRNFhsdnhiUUk0QVd4bnB2cWErdXFjTGJMRmtQZWNlMGc0MnRjaGw4bVgr?=
 =?utf-8?B?NXZ4VC93TUlaYlFVZkJQQ1BYUElyRE1Gd0xsTitHV1pvbXlCeElHNkVYUENz?=
 =?utf-8?B?dnJ5bkZZNkJEeHV5T0EzMzU1TnplZ2ZtNXkzajYxUzJEQ0J1YlppSlo4TGpV?=
 =?utf-8?B?bi9BUUJyS3dxbVJLM3FkWFBiUFhzT0JZMnVMOEsycmNRYi9sUEVFeGplUlpw?=
 =?utf-8?B?bWtUR3c2UUtzcFA1R0RiejE4NjdZRHFURVBzREVMbDNJV2VTcSt0M2dDcmll?=
 =?utf-8?B?OVdvTWJHMGJsc0FDS2x5MDBtYjlLbHFDR0NVZUF4M1gyaUUrbXRnVi9kQjNI?=
 =?utf-8?B?eGdsS0xrTCtzRjAyaVR1MXVaMkNUMDQrdlRqOUtmZytSWXZETUk1eU1CenBW?=
 =?utf-8?B?SzQ3V1BiRUI4dHNwcExNWUpXUzl5UWFXNHc4UGFPTnc0dFpSb09raTVuQVZI?=
 =?utf-8?B?UnE3cDZ3SWxCbFl5VzNKazNENnpnZ295SFludHluVE5tWVlQVEIxa3BzbDZS?=
 =?utf-8?B?QUFabGsrWk1lWXNyZ0ZMc0lGbGcxRzErdTJpK0dpTldXcHBXV0VJRWpHU0d0?=
 =?utf-8?B?V0F1OGUxc1hOaG1NSUFZMjk5VnlJM3NPa256Tk9wVDJ3WE9rdkxMTDZaVkQv?=
 =?utf-8?B?VnNFbWZ2UVg3RGhCL2ZxZ2dJNEFGMFV2aXgxdVhjOFphb2UzTEcySTA0RWFr?=
 =?utf-8?B?aUtqTXF3c2ZtZVArSjVscXVnbWdwUVFFV1c3clVCRDdzSWdkWHpVdVZZcStr?=
 =?utf-8?Q?KdA0vW8tfCHZWBTI2Wr6Cc8=3D?=
X-MS-Exchange-AntiSpam-ExternalHop-MessageData-ChunkCount: 1
X-MS-Exchange-AntiSpam-ExternalHop-MessageData-0: 
	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
X-OriginatorOrg: oracle.com
X-MS-Exchange-CrossTenant-Network-Message-Id: 6b0f67a7-6345-4c83-2688-08dc6043d3cd
X-MS-Exchange-CrossTenant-AuthSource: PH8PR10MB6290.namprd10.prod.outlook.com
X-MS-Exchange-CrossTenant-AuthAs: Internal
X-MS-Exchange-CrossTenant-OriginalArrivalTime: 19 Apr 2024 07:39:21.5201
 (UTC)
X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted
X-MS-Exchange-CrossTenant-Id: 4e2c6054-71cb-48f1-bd6c-3a9705aca71b
X-MS-Exchange-CrossTenant-MailboxType: HOSTED
X-MS-Exchange-CrossTenant-UserPrincipalName: a9Spe937Go9KEwiVV+X66OyPrxo/oqQqCVUYD4vpqWx80yjflM84ti80udAjFMdQ2o1icHvQzgOAtIqCUrT4WKpDDvOoRnbPs+JjVGlUrypejqjvoEeErMrp691c3jok
X-MS-Exchange-Transport-CrossTenantHeadersStamped: SJ0PR10MB4656
X-Proofpoint-Virus-Version: vendor=baseguard
 engine=ICAP:2.0.293,Aquarius:18.0.1011,Hydra:6.0.619,FMLib:17.11.176.26
 definitions=2024-04-19_04,2024-04-17_01,2023-05-22_02
X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 malwarescore=0 mlxlogscore=999
 bulkscore=0 spamscore=0 mlxscore=0 phishscore=0 adultscore=0
 suspectscore=0 classifier=spam adjust=0 reason=mlx scancount=1
 engine=8.12.0-2404010000 definitions=main-2404190055
X-Proofpoint-ORIG-GUID: PwZuqkOBMQYePltcUCbOY8ItoJI-dWsA
X-Proofpoint-GUID: PwZuqkOBMQYePltcUCbOY8ItoJI-dWsA

Hi Takashi,

On 19/04/24 12:14, Takashi Iwai wrote:
> On Thu, 18 Apr 2024 21:29:57 +0200,
> Helge Deller wrote:
>>
>> On 4/18/24 16:26, Takashi Iwai wrote:
>>> On Thu, 18 Apr 2024 16:06:52 +0200,
>>> Nam Cao wrote:
>>>>
>>>> On 2024-04-18 Harshit Mogalapalli wrote:
>>>>> While fuzzing 5.15.y kernel with Syzkaller, we noticed a INFO: task hung
>>>>> bug in fb_deferred_io_work()
>>>>
>>>> Which framebuffer device are you using exactly? It is possible that
>>>> the problem is with the device driver, not core framebuffer.
>>>
>>> Note that it was already known that using flush_delayed_work() caused
>>> a problem.  See the thread of the fix patch:
>>>     https://lore.kernel.org/all/20230129082856.22113-1-tiwai@suse.de/
>>
>> Harshit reported the hung tasks with kernel v5.15-stable, and can even reproduce
>> that issue with kernel v6.9-rc4 although it has all of your patches from
>> that referenced mail thread applied.
>> So, what does your statement that "it was already known that it causes problems" exactly mean?
>> Can it be fixed? Is someone looking into fixing it?
> 
> My original fix was intentionally with cancel_delayed_work_sync()
> because flush_delayed_work() didn't work.  We knew that it'd miss some
> last-minute queued change, but it's better than crash, so it was
> applied in that way.
> 

Thanks for sharing these details.

> Then later on, the commit 33cd6ea9c067 changed cancel_*() to
> flush_delayed_work() blindly, and the known problem resurfaced again.
> 

I have reverted that commit, but still could see some other task hung 
message as shared here on other reply:

https://lore.kernel.org/all/d2485cb9-277d-4b8e-9794-02f1efababc9@oracle.com/

Thanks,
Harshit
> 
> Takashi