linux-kernel - Re: [PATCH v11 4/8] fork: Add USER

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Message-ID: <3302e349-c2c5-d116-960d-3c0c4e713227@oracle.com>
Date:   Sun, 5 Feb 2023 10:06:04 -0600
From:   Mike Christie <michael.christie@...cle.com>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     hch@...radead.org, stefanha@...hat.com, jasowang@...hat.com,
        mst@...hat.com, sgarzare@...hat.com,
        virtualization@...ts.linux-foundation.org, brauner@...nel.org,
        ebiederm@...ssion.com, konrad.wilk@...cle.com,
        linux-kernel@...r.kernel.org, Christoph Hellwig <hch@....de>
Subject: Re: [PATCH v11 4/8] fork: Add USER_WORKER flag to ignore signals

On 2/2/23 6:19 PM, Linus Torvalds wrote:
> On Thu, Feb 2, 2023 at 3:25 PM Mike Christie
> <michael.christie@...cle.com> wrote:
>>
>> +       if (args->worker_flags & USER_WORKER_SIG_IGN)
>> +               ignore_signals(p);
> 
> Same comment as for the other case.
> 
> There are real reasons to avoid bitfields:
> 
>  - you can't pass addresses to them around
> 
>  - it's easier to read or assign multiple fields in one go
> 
>  - they are horrible for ABI issues due to the exact bit ordering and
> padding being very subtle
> 
> but none of those issues are relevant here, where it's a kernel-internal ABI.
> 
> All these use-cases seem to actually be testing one bit at a time, and
> the "assignments" are structure initializers for which named bitfields
> are actually perfect and just make the initializer more legible.
> 

Thanks for the comments. I see what you mean and have fixed those instances and
updated kthread as well.