Date: Wed, 30 Oct 2013 20:11:41 +0100
From: Peter Zijlstra <peterz@infradead.org>
To: Victor Kaplansky <VICTORK@il.ibm.com>
Cc: paulmck@linux.vnet.ibm.com, Anton Blanchard <anton@samba.org>,
        Benjamin Herrenschmidt <benh@kernel.crashing.org>,
        Frederic Weisbecker <fweisbec@gmail.com>,
        LKML <linux-kernel@vger.kernel.org>,
        Linux PPC dev <linuxppc-dev@ozlabs.org>,
        Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>,
        Michael Ellerman <michael@ellerman.id.au>,
        Michael Neuling <mikey@neuling.org>, Oleg Nesterov <oleg@redhat.com>
Subject: Re: perf events ring buffer memory barrier on powerpc
Message-ID: <20131030191141.GR2490@laptop.programming.kicks-ass.net>
References: <CAFTL4hxn47KFKZPLgKeBxxdaAbA4vg9QVzctuW4ZrSgmfX5bAQ@mail.gmail.com>
 <OFB9096CCA.68AAFFFB-ON42257C12.0044F107-42257C12.00457129@il.ibm.com>
 <20131028132634.GO19466@laptop.lan>
 <20131028163418.GD4126@linux.vnet.ibm.com>
 <20131028201735.GA15629@redhat.com>
 <OF58D85F5A.03E37A80-ON42257C12.0070E552-42257C12.00734308@il.ibm.com>
 <20131030092725.GL4126@linux.vnet.ibm.com>
 <OFC6B7100E.31C6B190-ON42257C14.004841C6-42257C14.004A0EA6@il.ibm.com>
 <20131030155116.GO16117@laptop.programming.kicks-ass.net>
 <20131030182930.GP2490@laptop.programming.kicks-ass.net>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20131030182930.GP2490@laptop.programming.kicks-ass.net>
User-Agent: Mutt/1.5.21 (2012-12-30)
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 690
Lines: 20

On Wed, Oct 30, 2013 at 07:29:30PM +0100, Peter Zijlstra wrote:
> +	page_shift = PAGE_SHIFT + page_order(rb);
> +
> +	handle->page = (offset >> page_shift) & (rb->nr_pages - 1);
> +
> +	offset &= page_shift - 1;

offset &= (1UL << page_shift) - 1;

Weird that it even appeared to work.. /me wonders if he even booted the
right kernel.

> +
> +	handle->addr = rb->data_pages[handle->page] + offset;
> +	handle->size = (1 << page_shift) - offset;
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/