linux-kernel - Re: patch "staging: r8188eu: Remove _enter/_exit_critical

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Date:   Tue, 7 Sep 2021 12:08:44 +0200
From:   Greg KH <gregkh@...uxfoundation.org>
To:     "Fabio M. De Francesco" <fmdefrancesco@...il.com>
Cc:     paskripkin@...il.com, linux-kernel@...r.kernel.org,
        linux-staging@...ts.linux.dev, larry.finger@...inger.net,
        phil@...lpotter.co.uk
Subject: Re: patch "staging: r8188eu: Remove _enter/_exit_critical_mutex()"
 added to staging-testing

On Tue, Sep 07, 2021 at 11:00:28AM +0200, Fabio M. De Francesco wrote:
> On Tuesday, September 7, 2021 8:56:52 AM CEST gregkh@...uxfoundation.org 
> wrote:
> > 
> > This is a note to let you know that I've just added the patch titled
> > 
> >     staging: r8188eu: Remove _enter/_exit_critical_mutex()
> > 
> > to my staging git tree which can be found at
> >     git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/staging.git
> > in the staging-testing branch.
> > 
> > The patch will show up in the next release of the linux-next tree
> > (usually sometime within the next 24 hours during the week.)
> > 
> > The patch will be merged to the staging-next branch sometime soon,
> > after it passes testing, and the merge window is open.
> > 
> > If you have any questions about this process, please let me know.
> > 
> > 
> > From d3c6dfb00bd9fe75f3a44246d6db7991f6443bac Mon Sep 17 00:00:00 2001
> > From: "Fabio M. De Francesco" <fmdefrancesco@...il.com>
> > Date: Sat, 28 Aug 2021 13:36:56 +0200
> > Subject: staging: r8188eu: Remove _enter/_exit_critical_mutex()
> > 
> > Remove _enter_critical_mutex() and _exit_critical_mutex(). They are
> > unnecessary wrappers, respectively to mutex_lock_interruptible() and
> > to mutex_unlock(). They also have an odd interface that takes an unused
> > argument named pirqL of type unsigned long.
> > The original code enters the critical section if the mutex API is
> > interrupted while waiting to acquire the lock; therefore it could lead
> > to a race condition. Use mutex_lock() because it is uninterruptible and
> > so avoid that above-mentioned potential race condition.
> 
> Dear Greg,
> 
> I've just read this message. Thank you for applying my patch. I really 
> appreciated that you trust the code :)
> 
> Unfortunately it makes me wonder if I should have added a "Fixes:" tag 
> because it (among other things) prevents a (possible while remote - I guess)
> bug. The code entered the critical section if the sleeping of the 
> interruptible mutex were interrupted by signals and so it could lead to race 
> conditions.
> 
> I have this doubt. Please let me know if I'd better redo the commit message 
> and add the above-mentioned tag.

Given the mess that is this driver right now, no, that's not needed at
all.  Only worry about that when you are fixing a real issue that should
be backported to older kernel releases.

thanks,

greg k-h