| Message ID | 20191121072910.31665-1-bibby.hsieh@mediatek.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | soc: mediatek: cmdq: avoid racing condition with mutex | expand |
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@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); > > 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; > }; > > /**
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@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); > > > > 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; > > }; > > > > /** >
On Tue, Dec 3, 2019 at 8:22 PM CK Hu <ck.hu@mediatek.com> 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. > mbox_client_txdone should be called only when the client _knows_ the message has been sent. There is difference between knowing when tx is done, and assuming tx-done because there is no way of knowing it. Your issue arises because you immediately call mbox_client_txdone after mbox_send_message, which may be the only way to do it but that doesn't mean you shouldn't have to take any other precautions (like a mutex). So I think your patch is reasonable. Cheers! > 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@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); > > > > 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; > > }; > > > > /** >
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; > }; > > /**
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; }; /**
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(+)