linux-kernel - Re: [PATCH] dmaengine: pl330: fix the race condition in pl330 driver.

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Date:	Mon, 30 Mar 2015 22:55:46 +0530
From:	Vinod Koul <vinod.koul@...el.com>
To:	Jassi Brar <jassisinghbrar@...il.com>
Cc:	Scott Branden <sbranden@...adcom.com>,
	Dan Williams <dan.j.williams@...el.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	ismail <ismail@...adcom.com>, Anatol Pomazao <anatol@...gle.com>,
	Dmitry Torokhov <dtor@...gle.com>,
	bcm-kernel-feedback-list@...adcom.com,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH] dmaengine: pl330: fix the race condition in pl330 driver.

On Mon, Mar 30, 2015 at 10:17:17PM +0530, Jassi Brar wrote:
> On Fri, Mar 27, 2015 at 5:25 AM, Scott Branden <sbranden@...adcom.com> wrote:
> > From: ismail <ismail@...adcom.com>
> >
> > Update the thread running index before issuing the
> > GO command to the DMAC.
> >
> > Tested-by: Mohamed Ismail Abdul Packir Mohamed <ismail@...adcom.com>
> > Reviewed-by: Ray Jui <rjui@...adcom.com>
> > Reviewed-by: Arun Parameswaran <aparames@...adcom.com>
> > Reviewed-by: Scott Branden <sbranden@...adcom.com>
> > Signed-off-by: Scott Branden <sbranden@...adcom.com>
> > Signed-off-by: Mohamed Ismail Abdul Packir Mohamed <ismail@...adcom.com>
> > ---
> >  drivers/dma/pl330.c | 4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/dma/pl330.c b/drivers/dma/pl330.c
> > index 0e1f567..631642d 100644
> > --- a/drivers/dma/pl330.c
> > +++ b/drivers/dma/pl330.c
> > @@ -1072,11 +1072,11 @@ static bool _trigger(struct pl330_thread *thrd)
> >         /* Set to generate interrupts for SEV */
> >         writel(readl(regs + INTEN) | (1 << thrd->ev), regs + INTEN);
> >
> > +       thrd->req_running = idx;
> > +
> >         /* Only manager can execute GO */
> >         _execute_DBGINSN(thrd, insn, true);
> >
> > -       thrd->req_running = idx;
> > -
> It would help to know what the behavior looks like before and after
> the patch. If anything we should look at locking rather the
> reordering.
Yes that ia fair request, looking at changelog it is hard to understand the
issue seen?

-- 
~Vinod

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