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

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Message-ID: <20190212144722.6bc516db@gandalf.local.home>
Date:   Tue, 12 Feb 2019 14:47:22 -0500
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Joe Perches <joe@...ches.com>
Cc:     Petr Mladek <pmladek@...e.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 09:58:25 -0800
Joe Perches <joe@...ches.com> wrote:

> On Tue, 2019-02-12 at 14:00 +0100, Petr Mladek 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.  
> 
> That's an argument?.
> 
> Refactoring is good, but you need to add
> __always_inline here.
> 

If a single function call causes this to overflow the stack, then the
code is already broken to begin with.

-- Steve