From: CK Hu <ck.hu@mediatek.com>
To: Bibby Hsieh <bibby.hsieh@mediatek.com>
Cc: devicetree@vger.kernel.org,
Nicolas Boichat <drinkcat@chromium.org>,
srv_heupstream@mediatek.com,
Jassi Brar <jassisinghbrar@gmail.com>,
linux-kernel@vger.kernel.org,
Houlong Wei <houlong.wei@mediatek.com>,
Dennis-YC Hsieh <dennis-yc.hsieh@mediatek.com>,
Rob Herring <robh+dt@kernel.org>,
linux-mediatek@lists.infradead.org,
Matthias Brugger <matthias.bgg@gmail.com>,
linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH] soc: mediatek: cmdq: avoid racing condition with mutex
Date: Mon, 30 Dec 2019 14:44:13 +0800 [thread overview]
Message-ID: <1577688253.17931.11.camel@mtksdaap41> (raw)
In-Reply-To: <20191121072910.31665-1-bibby.hsieh@mediatek.com>
Hi, Bibby:
On Thu, 2019-11-21 at 15:29 +0800, Bibby Hsieh wrote:
> If cmdq client is multi thread user, racing will occur without mutex
> protection. It will make the C message queued in mailbox's queue
> always need D message's triggering.
>
> Thread A Thread B Thread C Thread D...
> -----------------------------------------------------------------------------------
> mbox_send_message()
> send_data()
> mbox_send_message()
> *exit
> mbox_send_message()
> *exit
> mbox_client_txdone()
> tx_tick()
> mbox_client_txdone()
> tx_tick()
> mbox_client_txdone()
> tx_tick()
> msg_submit()
> send_data()
> msg_submit()
> *exit
> msg_submit()
> *exit
> -----------------------------------------------------------------------------------
>
> Signed-off-by: Bibby Hsieh <bibby.hsieh@mediatek.com>
> ---
> drivers/soc/mediatek/mtk-cmdq-helper.c | 3 +++
> include/linux/soc/mediatek/mtk-cmdq.h | 1 +
> 2 files changed, 4 insertions(+)
>
> diff --git a/drivers/soc/mediatek/mtk-cmdq-helper.c b/drivers/soc/mediatek/mtk-cmdq-helper.c
> index 9add0fd5fa6c..9e35e0beffaa 100644
> --- a/drivers/soc/mediatek/mtk-cmdq-helper.c
> +++ b/drivers/soc/mediatek/mtk-cmdq-helper.c
> @@ -81,6 +81,7 @@ struct cmdq_client *cmdq_mbox_create(struct device *dev, int index, u32 timeout)
> client->client.dev = dev;
> client->client.tx_block = false;
> client->chan = mbox_request_channel(&client->client, index);
> + mutex_init(&client->mutex);
>
> if (IS_ERR(client->chan)) {
> long err;
> @@ -352,9 +353,11 @@ int cmdq_pkt_flush_async(struct cmdq_pkt *pkt, cmdq_async_flush_cb cb,
> spin_unlock_irqrestore(&client->lock, flags);
> }
>
> + mutex_lock(&client->mutex);
> mbox_send_message(client->chan, pkt);
> /* We can send next packet immediately, so just call txdone. */
> mbox_client_txdone(client->chan, 0);
> + mutex_unlock(&client->mutex);
In [1], Mediatek DRM is the first client to use cmdq and it already has
its own mutex to protect this. I think helper is something help many
user but now I just see Mediatek MDP [2] need this. For DRM, there are
so many useless code in cmdq_pkt_flush_async(). DRM does not need the
timer to check timeout. DRM could do dma_sync_single_for_cpu() in its
callback and need not to create a intermediate callback to do this. I
would agree this patch only when I see two or more user need this.
[1]
https://github.com/ckhu-mediatek/linux.git-tags/commit/4df12ed1866d1104f631e06218bd15fde512a79e
[2] https://patchwork.kernel.org/patch/10945609/
Regards,
CK
>
> return 0;
> }
> diff --git a/include/linux/soc/mediatek/mtk-cmdq.h b/include/linux/soc/mediatek/mtk-cmdq.h
> index a74c1d5acdf3..0f9071cd1bc7 100644
> --- a/include/linux/soc/mediatek/mtk-cmdq.h
> +++ b/include/linux/soc/mediatek/mtk-cmdq.h
> @@ -28,6 +28,7 @@ struct cmdq_client {
> struct mbox_chan *chan;
> struct timer_list timer;
> u32 timeout_ms; /* in unit of microsecond */
> + struct mutex mutex;
> };
>
> /**
_______________________________________________
Linux-mediatek mailing list
Linux-mediatek@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-mediatek
prev parent reply other threads:[~2019-12-30 6:44 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-21 7:29 [PATCH] soc: mediatek: cmdq: avoid racing condition with mutex Bibby Hsieh
2019-12-04 2:22 ` CK Hu
2019-12-30 2:02 ` CK Hu
2019-12-30 3:28 ` Jassi Brar
2019-12-30 6:44 ` CK Hu [this message]
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=1577688253.17931.11.camel@mtksdaap41 \
--to=ck.hu@mediatek.com \
--cc=bibby.hsieh@mediatek.com \
--cc=dennis-yc.hsieh@mediatek.com \
--cc=devicetree@vger.kernel.org \
--cc=drinkcat@chromium.org \
--cc=houlong.wei@mediatek.com \
--cc=jassisinghbrar@gmail.com \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mediatek@lists.infradead.org \
--cc=matthias.bgg@gmail.com \
--cc=robh+dt@kernel.org \
--cc=srv_heupstream@mediatek.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).