Date: Tue, 24 Feb 2015 14:16:21 -0800 (PST)
From: David Rientjes <rientjes@google.com>
To: Heinrich Schuchardt <xypron.glpk@gmx.de>
cc: Andrew Morton <akpm@linux-foundation.org>,
        Aaron Tomlin <atomlin@redhat.com>,
        Andy Lutomirski <luto@amacapital.net>,
        Davidlohr Bueso <dave@stgolabs.net>,
        "David S. Miller" <davem@davemloft.net>,
        Fabian Frederick <fabf@skynet.be>, Guenter Roeck <linux@roeck-us.net>,
        "H. Peter Anvin" <hpa@zytor.com>, Ingo Molnar <mingo@kernel.org>,
        Jens Axboe <axboe@fb.com>, Joe Perches <joe@perches.com>,
        Johannes Weiner <hannes@cmpxchg.org>,
        Kees Cook <keescook@chromium.org>,
        Michael Marineau <mike@marineau.org>, Oleg Nesterov <oleg@redhat.com>,
        "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Prarit Bhargava <prarit@redhat.com>, Rik van Riel <riel@redhat.com>,
        Rusty Russell <rusty@rustcorp.com.au>,
        Steven Rostedt <rostedt@goodmis.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Vladimir Davydov <vdavydov@parallels.com>,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/3 v5] kernel/fork.c: new function for max_threads
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On Tue, 24 Feb 2015, Heinrich Schuchardt wrote:

> > I'm afraid I don't understand this.  The intent of the patch is to 
> > separate the max_threads logic into a new function, correct?  If that's 
> > true, then I don't understand why UINT_MAX is being introduced into this 
> > path and passed to the new function when it is ignored.
> > 
> > I think it would be better to simply keep passing mempages to fork_init() 
> > and then pass it to set_max_threads() where max_threads actually gets set 
> > using the argument passed.  At least, the code would then match the intent 
> > of the patch.
> > 
> Please, read patch 2/3 which provides support for the argument,
> and patch 3/3 that finally needs it.
> 

The problem is with the structure of your patchset.  You want three 
patches.  There's one bugfix patch, a preparation patch, and a feature 
patch.  The bugfix patch should come first so that it can be applied, 
possibly, to stable kernels and doesn't depend on unnecessary preparation 
patches for features.

1/3: change the implementation of fork_init(), with commentary, to avoid 
the divide by zero on certain arches, enforce the limits, and deal with 
variable types to prevent overflow.  This is the most urgent patch and 
fixes a bug.

2/3: simply extract the fixed fork_init() implementation into a new 
set_max_threads() in preparation to use it for threads-max, (hint: 
UINT_MAX and ignored arguments should not appear in this patch),

3/3: use the new set_max_threads() implementation for threads-max with an 
update to the documentation.
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