linux-kernel - Re: [PATCH v6 5/9] vsprintf: Factor out %pV handler as va

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Message-ID: <20190212093204.1bddf4a8@gandalf.local.home>
Date:   Tue, 12 Feb 2019 09:32:04 -0500
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Petr Mladek <pmladek@...e.com>
Cc:     Joe Perches <joe@...ches.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Rasmus Villemoes <linux@...musvillemoes.dk>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        "Tobin C . Harding" <me@...in.cc>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Michal Hocko <mhocko@...e.cz>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v6 5/9] vsprintf: Factor out %pV handler as va_format()

On Tue, 12 Feb 2019 14:00:30 +0100
Petr Mladek <pmladek@...e.com> wrote:

> On Fri 2019-02-08 09:11:17, Joe Perches wrote:
> > On Fri, 2019-02-08 at 16:23 +0100, Petr Mladek wrote:  
> > > Move the code from the long pointer() function. We are going to improve
> > > error handling that will make it more complicated.
> > > 
> > > This patch does not change the existing behavior.  
> > 
> > But doesn't this increase stack use?
> > %pV is recursive and increasing the stack is undesired
> > for this use.  
> 
> %pV handler is stack sensitive because the entire vsnprintf()
> machinery is called recursively. This one extra call does
> not make it much worse.
>

Not to mention that if it is the only static call, gcc will most likely
just keep it inlined. Could add an inline annotation just to be
paranoid.

-- Steve