linux-kernel - Re: [sgi-xp] Missing break or false positive?

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Date:   Wed, 20 Mar 2019 10:36:04 -0500
From:   "Gustavo A. R. Silva" <gustavo@...eddedor.com>
To:     Robin Holt <robinmholt@...il.com>
Cc:     Cliff Whickman <cpw@....com>, Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Kees Cook <keescook@...omium.org>
Subject: Re: [sgi-xp] Missing break or false positive?



On 3/20/19 10:23 AM, Robin Holt wrote:
> I am sorry for my delayed response.  I missed the earlier email.
> 
> On Wed, Mar 20, 2019 at 9:37 AM Gustavo A. R. Silva
> <gustavo@...eddedor.com> wrote:
>>
> ...
>>> I'm taking a look into the following piece of code in drivers/misc/sgi-xp/xpc_uv.c:
> ...
>>> and I'm trying to figure out if the following warning is due to a missing break
>>> at the end of the case, or if this is just a false positive and a /* fall through */
>>> annotation should be added:
> 
> The fall-through is by design.  The protocol previously had a windows
> of failure where a connection
> could be in the process of being established and a failure could be
> detected prior to the
> handling of the establishment message.  I added the new open complete
> message and leveraged
> the fall-through to mark the connection established.
> 

Great. I see now.

> Please let me know if you do not intend to submit a patch for this.
> 

I will send a patch to add the fall-through comment and fix the following
warning:

drivers/misc/sgi-xp/xpc_uv.c: In function ‘xpc_handle_activate_mq_msg_uv’:
drivers/misc/sgi-xp/xpc_uv.c:573:3: warning: this statement may fall through [-Wimplicit-fallthrough=]
   xpc_wakeup_channel_mgr(part);
   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
drivers/misc/sgi-xp/xpc_uv.c:575:2: note: here
  case XPC_ACTIVATE_MQ_MSG_MARK_ENGAGED_UV:
  ^~~~

Notice that this is part of the ongoing efforts to enable -Wimplicit-fallthrough.

Thanks, Robin.
--
Gustavo