linux-kernel - Re: [RFC PATCH] workqueue: Fix rescuer task's name truncated

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Date: Mon, 13 May 2024 10:28:05 +0800
From: Wenchao Hao <haowenchao22@...il.com>
To: Aaron Tomlin <atomlin@...mlin.com>, Wenchao Hao <haowenchao2@...wei.com>
Cc: Tejun Heo <tj@...nel.org>, Lai Jiangshan <jiangshanlai@...il.com>,
 linux-kernel@...r.kernel.org, neelx@...hat.com
Subject: Re: [RFC PATCH] workqueue: Fix rescuer task's name truncated

On 2024/5/11 22:15, Aaron Tomlin wrote:
> On Wed, Apr 24, 2024 at 02:21:04AM GMT, Wenchao Hao wrote:
>> Task comm of task is limitted to 16, prefix "kworker/R-" is added for
>> rescuer worker's task, which cause most task name is truncated as
>> following:
>>
>> root   81  0.0  0.0  0  0 ?   I<   11:18   0:00 [kworker/R-xprti]
>> root   82  0.0  0.0  0  0 ?   I<   11:18   0:00 [kworker/R-cfg80]
>> root   85  0.0  0.0  0  0 ?   I<   11:18   0:00 [kworker/R-nfsio]
>> root   86  0.0  0.0  0  0 ?   I<   11:18   0:00 [kworker/R-xfsal]
>> root   87  0.0  0.0  0  0 ?   I<   11:18   0:00 [kworker/R-xfs_m]
>> root   88  0.0  0.0  0  0 ?   I<   11:18   0:00 [kworker/R-acpi_]
>> root   93  0.0  0.0  0  0 ?   I<   11:18   0:00 [kworker/R-iscsi]
>> root   95  0.0  0.0  0  0 ?   I<   11:18   0:00 [kworker/R-scsi_]
>> root   97  0.0  0.0  0  0 ?   I<   11:18   0:00 [kworker/R-scsi_]
>> root   99  0.0  0.0  0  0 ?   I<   11:18   0:00 [kworker/R-scsi_]
>>
>> I want to fix this issue by split rescuer name to 2 part like other
>> kworker, the normal part is "kworker/R" which is set to task_struct's comm,
>> another part is wq->name which is added to kworker's desc. These 2 parts
>> would be merged in wq_worker_comm().
>>
>> Fixes: b6a46f7263bd ("workqueue: Rename rescuer kworker")
>>
>> Signed-off-by: Wenchao Hao <haowenchao2@...wei.com>
>> ---
>>   kernel/workqueue.c | 6 +++++-
>>   1 file changed, 5 insertions(+), 1 deletion(-)
>>
>> diff --git a/kernel/workqueue.c b/kernel/workqueue.c
>> index 0066c8f6c154..0ce9e8597a4d 100644
>> --- a/kernel/workqueue.c
>> +++ b/kernel/workqueue.c
>> @@ -5430,7 +5430,7 @@ static int init_rescuer(struct workqueue_struct *wq)
>>   	}
>>   
>>   	rescuer->rescue_wq = wq;
>> -	rescuer->task = kthread_create(rescuer_thread, rescuer, "kworker/R-%s", wq->name);
>> +	rescuer->task = kthread_create(rescuer_thread, rescuer, "kworker/R");
>>   	if (IS_ERR(rescuer->task)) {
>>   		ret = PTR_ERR(rescuer->task);
>>   		pr_err("workqueue: Failed to create a rescuer kthread for wq \"%s\": %pe",
>> @@ -5439,6 +5439,8 @@ static int init_rescuer(struct workqueue_struct *wq)
>>   		return ret;
>>   	}
>>   
>> +	snprintf(rescuer->desc, sizeof(rescuer->desc), "%s", wq->name);
>> +
>>   	wq->rescuer = rescuer;
>>   	if (wq->flags & WQ_UNBOUND)
>>   		kthread_bind_mask(rescuer->task, wq_unbound_cpumask);
>> @@ -6289,6 +6291,8 @@ void wq_worker_comm(char *buf, size_t size, struct task_struct *task)
>>   						  worker->desc);
>>   			}
>>   			raw_spin_unlock_irq(&pool->lock);
>> +		} else if (worker->desc[0] != '\0') {
>> +			scnprintf(buf + off, size - off, "-%s", worker->desc);
>>   		}
>>   	}
>>   
>> -- 
> 
> Reviewed-by: Aaron Tomlin <atomlin@...mlin.com>
> 
Thanks for your review, I would add your Reviewed-by and remove the RFC 
tags, then post again.