From: Laxman Dewangan <ldewangan@nvidia.com>
To: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Vinod Koul <vinod.koul@intel.com>, Dan Williams <djbw@fb.com>,
Stephen Warren <swarren@wwwdotorg.org>,
"linux-tegra@vger.kernel.org" <linux-tegra@vger.kernel.org>
Subject: Re: [PATCH 09/12] tegra20-apb-dma: remove useless use of lock
Date: Wed, 29 May 2013 16:26:28 +0530 [thread overview]
Message-ID: <51A5DEDC.4040606@nvidia.com> (raw)
In-Reply-To: <1369656882-25241-10-git-send-email-andriy.shevchenko@linux.intel.com>
On Monday 27 May 2013 05:44 PM, Andy Shevchenko wrote:
> Accordingly to dma_cookie_status() description locking is not required.
>
I think we need lock here:
From isr handler, we call dma_cookie_complete() which is in
spin-locked. This function updates tx->chan->completed_cookie = tx->cookie;
In tegra_dma_tx_status(), we check for dma_cookie_status() which access
the chan->completed_cookie; and it decides status based on this
As the access of chan->completed_cookie are from different context, we
need this locking.
But did not get why it is documented as locking is not require if shared
variable is getting changed/access from different context simultaneously.
next prev parent reply other threads:[~2013-05-29 10:56 UTC|newest]
Thread overview: 43+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-05-27 12:14 [PATCH 00/12] dma: various minor clean ups for slave drivers Andy Shevchenko
2013-05-27 12:14 ` Andy Shevchenko
2013-05-27 12:14 ` [PATCH 01/12] imx-sdma: remove useless variable Andy Shevchenko
2013-05-27 12:14 ` [PATCH 02/12] mxs-dma: " Andy Shevchenko
2013-05-27 12:14 ` [PATCH 03/12] edma: no need to assign residue to 0 explicitly Andy Shevchenko
2013-05-27 12:14 ` [PATCH 04/12] ep93xx_dma: remove useless use of lock Andy Shevchenko
2013-05-27 12:14 ` [PATCH 05/12] fsldma: " Andy Shevchenko
2013-05-27 12:14 ` Andy Shevchenko
2013-05-27 12:14 ` [PATCH 06/12] mmp_pdma: " Andy Shevchenko
2013-05-27 12:14 ` [PATCH 07/12] mpc512x_dma: " Andy Shevchenko
2013-05-27 12:14 ` [PATCH 08/12] pch_dma: " Andy Shevchenko
2013-05-27 12:14 ` [PATCH 09/12] tegra20-apb-dma: " Andy Shevchenko
2013-05-29 10:56 ` Laxman Dewangan [this message]
[not found] ` <51A5DEDC.4040606-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org>
2013-05-29 13:42 ` Andy Shevchenko
2013-05-29 13:42 ` Andy Shevchenko
2013-05-27 12:14 ` [PATCH 10/12] ipu_idmac: re-use dma_cookie_status() Andy Shevchenko
2013-05-29 2:19 ` Shawn Guo
2013-05-27 12:14 ` [PATCH 11/12] mmp_tdma: set cookies as well when asked for tx status Andy Shevchenko
2013-05-27 12:14 ` [PATCH 12/12] txx9dmac: return DMA_SUCCESS immediately from device_tx_status() Andy Shevchenko
[not found] ` <1369656882-25241-1-git-send-email-andriy.shevchenko-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>
2013-05-30 17:47 ` [PATCH 00/12] dma: various minor clean ups for slave drivers Vinod Koul
2013-05-30 17:47 ` Vinod Koul
2013-05-30 17:47 ` Vinod Koul
[not found] ` <20130530174727.GE3767-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
2013-05-30 18:32 ` Andy Shevchenko
2013-05-30 18:32 ` Andy Shevchenko
2013-05-30 18:32 ` Andy Shevchenko
[not found] ` <CAHp75VcZCVskWnQuNeO4A0keZJS27vaWe5zTDomAgSa_ezyUQQ-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2013-07-15 9:37 ` Vinod Koul
2013-07-15 9:37 ` Vinod Koul
2013-07-15 9:37 ` Vinod Koul
[not found] ` <20130715093748.GO16653-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
2013-07-15 10:21 ` Andy Shevchenko
2013-07-15 10:21 ` Andy Shevchenko
2013-07-15 10:21 ` Andy Shevchenko
2013-07-15 9:59 ` Vinod Koul
2013-07-15 9:59 ` Vinod Koul
2013-07-15 9:59 ` Vinod Koul
2013-06-01 0:09 ` Dan Williams
2013-06-01 0:09 ` Dan Williams
2013-06-01 0:09 ` Dan Williams
[not found] ` <CAA9_cmdNiLfJjv-8Mh-Xb1ifZb4aw_9NGCVW6aWsfq6BN-DYyQ-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2013-07-15 9:33 ` Vinod Koul
2013-07-15 9:33 ` Vinod Koul
2013-07-15 9:33 ` Vinod Koul
2013-07-10 7:54 ` Andy Shevchenko
2013-07-10 7:54 ` Andy Shevchenko
2013-07-10 7:54 ` Andy Shevchenko
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