From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
To: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>,
"linux-mm@kvack.org" <linux-mm@kvack.org>,
LKML <linux-kernel@vger.kernel.org>,
Matt Mackall <mpm@selenic.com>
Subject: Re: Memory allocator semantics
Date: Fri, 14 Feb 2014 09:30:39 -0800 [thread overview]
Message-ID: <20140214173038.GR4250@linux.vnet.ibm.com> (raw)
In-Reply-To: <alpine.DEB.2.10.1402111242380.28186@nuc>
On Tue, Feb 11, 2014 at 12:43:35PM -0600, Christoph Lameter wrote:
> On Tue, 11 Feb 2014, Pekka Enberg wrote:
>
> > So again, there's nothing in (A) that the memory allocator is
> > concerned about. kmalloc() makes no guarantees whatsoever about the
> > visibility of "r1" across CPUs. If you're saying that there's an
> > implicit barrier between kmalloc() and kfree(), that's an unintended
> > side-effect, not a design decision AFAICT.
>
> I am not sure that this side effect necessarily happens. The SLUB fastpath
> does not disable interrupts and only uses a cmpxchg without lock
> semantics.
That tells me what I need to know. Users should definitely not try a
"drive-by kfree()" of something that was concurrently allocated. ;-)
Thanx, Paul
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WARNING: multiple messages have this Message-ID (diff)
From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
To: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>,
"linux-mm@kvack.org" <linux-mm@kvack.org>,
LKML <linux-kernel@vger.kernel.org>,
Matt Mackall <mpm@selenic.com>
Subject: Re: Memory allocator semantics
Date: Fri, 14 Feb 2014 09:30:39 -0800 [thread overview]
Message-ID: <20140214173038.GR4250@linux.vnet.ibm.com> (raw)
In-Reply-To: <alpine.DEB.2.10.1402111242380.28186@nuc>
On Tue, Feb 11, 2014 at 12:43:35PM -0600, Christoph Lameter wrote:
> On Tue, 11 Feb 2014, Pekka Enberg wrote:
>
> > So again, there's nothing in (A) that the memory allocator is
> > concerned about. kmalloc() makes no guarantees whatsoever about the
> > visibility of "r1" across CPUs. If you're saying that there's an
> > implicit barrier between kmalloc() and kfree(), that's an unintended
> > side-effect, not a design decision AFAICT.
>
> I am not sure that this side effect necessarily happens. The SLUB fastpath
> does not disable interrupts and only uses a cmpxchg without lock
> semantics.
That tells me what I need to know. Users should definitely not try a
"drive-by kfree()" of something that was concurrently allocated. ;-)
Thanx, Paul
next prev parent reply other threads:[~2014-02-14 17:30 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-01-02 20:33 Memory allocator semantics Paul E. McKenney
2014-01-02 20:33 ` Paul E. McKenney
2014-01-03 3:39 ` Josh Triplett
2014-01-03 3:39 ` Josh Triplett
2014-01-03 5:14 ` Paul E. McKenney
2014-01-03 5:14 ` Paul E. McKenney
2014-01-03 5:47 ` Josh Triplett
2014-01-03 5:47 ` Josh Triplett
2014-01-03 7:57 ` Paul E. McKenney
2014-01-03 7:57 ` Paul E. McKenney
2014-01-03 8:42 ` Josh Triplett
2014-01-03 8:42 ` Josh Triplett
2014-02-08 10:27 ` Pekka Enberg
2014-02-08 10:27 ` Pekka Enberg
2014-02-09 2:00 ` Paul E. McKenney
2014-02-09 2:00 ` Paul E. McKenney
2014-02-11 8:50 ` Pekka Enberg
2014-02-11 8:50 ` Pekka Enberg
2014-02-11 12:09 ` Paul E. McKenney
2014-02-11 12:09 ` Paul E. McKenney
2014-02-11 18:43 ` Christoph Lameter
2014-02-11 18:43 ` Christoph Lameter
2014-02-14 17:30 ` Paul E. McKenney [this message]
2014-02-14 17:30 ` Paul E. McKenney
2014-02-10 19:07 ` Christoph Lameter
2014-02-10 19:07 ` Christoph Lameter
2014-02-11 12:14 ` Paul E. McKenney
2014-02-11 12:14 ` Paul E. McKenney
2014-02-11 13:20 ` Pekka Enberg
2014-02-11 13:20 ` Pekka Enberg
2014-02-11 15:01 ` Paul E. McKenney
2014-02-11 15:01 ` Paul E. McKenney
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