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From: Ingo Molnar <mingo@kernel.org>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: Rusty Russell <rusty@rustcorp.com.au>,
	LKML <linux-kernel@vger.kernel.org>,
	Peter Zijlstra <peterz@infradead.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
	Xunlei Pang <xlpang@redhat.com>
Subject: Re: [RFC][PATCH] Add __GFP_ZERO to alloc_cpumask_var_node() if ptr is zero
Date: Fri, 4 Dec 2015 08:34:37 +0100	[thread overview]
Message-ID: <20151204073437.GA24827@gmail.com> (raw)
In-Reply-To: <20151203213745.52f21886@gandalf.local.home>


* Steven Rostedt <rostedt@goodmis.org> wrote:

> On Fri, 04 Dec 2015 12:05:12 +1030
> Rusty Russell <rusty@rustcorp.com.au> wrote:
> 
> > This is clever, but I would advise against such subtle code.  We will never be 
> > able to remove this code once it is in.
> > 
> > Would suggest making the non-CPUMASK_OFFSTACK stubs write garbage into the 
> > cpumasks instead, iff !(flags & __GFP_ZERO).
>
> I actually thought of the same thing, but thought it was a bit harsh. If others 
> think that's a better solution, then I'll submit a patch to do that.

That just makes things more fragile - 'garbage' will spread the breakage, and if 
the breakage is subtle, it will spread subtle breakage.

So why not use a kzmalloc_node() [equivalent] call instead of kmalloc_node(), to 
make sure it's all zeroed instead of uninitialized?

Thanks,

	Ingo

  reply	other threads:[~2015-12-04  7:34 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-12-03 22:24 [RFC][PATCH] Add __GFP_ZERO to alloc_cpumask_var_node() if ptr is zero Steven Rostedt
2015-12-04  1:35 ` Rusty Russell
2015-12-04  2:37   ` Steven Rostedt
2015-12-04  7:34     ` Ingo Molnar [this message]
2015-12-04 20:30       ` Rusty Russell
2015-12-06 17:29         ` Ingo Molnar
2015-12-07  1:56           ` Rusty Russell
2015-12-07  8:23             ` Ingo Molnar

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