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Date: Mon, 30 Dec 2019 10:02:41 +0800 From: CK Hu <ck.hu@...iatek.com> To: Bibby Hsieh <bibby.hsieh@...iatek.com> CC: Jassi Brar <jassisinghbrar@...il.com>, Matthias Brugger <matthias.bgg@...il.com>, Rob Herring <robh+dt@...nel.org>, <devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>, <linux-arm-kernel@...ts.infradead.org>, <linux-mediatek@...ts.infradead.org>, <srv_heupstream@...iatek.com>, Nicolas Boichat <drinkcat@...omium.org>, Dennis-YC Hsieh <dennis-yc.hsieh@...iatek.com>, Houlong Wei <houlong.wei@...iatek.com> Subject: Re: [PATCH] soc: mediatek: cmdq: avoid racing condition with mutex Hi, Jassi: Ping again. Are mbox_send_message() and mbox_client_txdone() thread-safe? If these two are thread-safe, this bug should be fixed in mailbox core not client. Regards, CK On Wed, 2019-12-04 at 10:22 +0800, CK Hu wrote: > Hi, Jassi: > > Are mbox_send_message() and mbox_client_txdone() thread-safe? If these > two are thread-safe, this bug should be fixed in mailbox core not > client. > > Regards, > CK > > 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@...iatek.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); > > > > 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; > > }; > > > > /** >
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