linux-kernel - Re: [PATCH 03/11] kthread: Pass in the thread's name during creation

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Message-ID: <253eda66-b866-c233-335f-ff820e7ad2b2@oracle.com>
Date:   Sat, 11 Mar 2023 19:48:02 -0600
From:   Mike Christie <michael.christie@...cle.com>
To:     Christian Brauner <brauner@...nel.org>
Cc:     hch@...radead.org, stefanha@...hat.com, jasowang@...hat.com,
        mst@...hat.com, sgarzare@...hat.com,
        virtualization@...ts.linux-foundation.org, ebiederm@...ssion.com,
        torvalds@...ux-foundation.org, konrad.wilk@...cle.com,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 03/11] kthread: Pass in the thread's name during creation

On 3/11/23 10:11 AM, michael.christie@...cle.com wrote:
> On 3/11/23 2:53 AM, Christian Brauner wrote:
>> On Fri, Mar 10, 2023 at 04:03:24PM -0600, Mike Christie wrote:
>>> This has us pass in the thread's name during creation in kernel_thread.
>>>
>>> Signed-off-by: Mike Christie <michael.christie@...cle.com>
>>> ---
>>>  kernel/kthread.c | 35 ++++++++++++++---------------------
>>>  1 file changed, 14 insertions(+), 21 deletions(-)
>>>
>>> diff --git a/kernel/kthread.c b/kernel/kthread.c
>>> index 63574cee925e..831a55b406d8 100644
>>> --- a/kernel/kthread.c
>>> +++ b/kernel/kthread.c
>>> @@ -38,6 +38,7 @@ struct task_struct *kthreadd_task;
>>>  struct kthread_create_info
>>>  {
>>>  	/* Information passed to kthread() from kthreadd. */
>>> +	char *full_name;
>>>  	int (*threadfn)(void *data);
>>>  	void *data;
>>>  	int node;
>>> @@ -343,10 +344,15 @@ static int kthread(void *_create)
>>>  	/* Release the structure when caller killed by a fatal signal. */
>>>  	done = xchg(&create->done, NULL);
>>>  	if (!done) {
>>> +		kfree(create->full_name);
>>>  		kfree(create);
>>>  		kthread_exit(-EINTR);
>>>  	}
>>>  
>>> +	if (strlen(create->full_name) >= TASK_COMM_LEN)
>>> +		self->full_name = create->full_name;
>>> +	else
>>> +		kfree(create->full_name);
>>
>> This is monir but wwiw, this looks suspicious when reading it without
>> more context. It took me a while to see that kthread->full_name is
>> intended to store the untruncated name only if truncation actually needs
>> to happen. So either we should always initialize this or we should add a
>> comment. You can just send a tiny patch that I can fold into this one so
>> you don't have to resend the whole series...

Hey Christian, here is a patch you can fold into the original. Thanks
for your help.


>From ac82986ec4e7faae245ec48cb9213a4ca1c1d4d6 Mon Sep 17 00:00:00 2001
From: Mike Christie <michael.christie@...cle.com>
Date: Sat, 11 Mar 2023 16:14:24 -0600
Subject: [PATCH] kthread: Always save the full_name

Simplify the kthread name handling by always using the full_name.
---
 kernel/kthread.c | 5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/kernel/kthread.c b/kernel/kthread.c
index 831a55b406d8..5596ec3f75cf 100644
--- a/kernel/kthread.c
+++ b/kernel/kthread.c
@@ -349,10 +349,7 @@ static int kthread(void *_create)
 		kthread_exit(-EINTR);
 	}
 
-	if (strlen(create->full_name) >= TASK_COMM_LEN)
-		self->full_name = create->full_name;
-	else
-		kfree(create->full_name);
+	self->full_name = create->full_name;
 	self->threadfn = threadfn;
 	self->data = data;