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[PATCH net v2] phy: mscc: Stop taking ts_lock for tx_queue and use its own lock

Horatiu Vultur posted 1 patch 1 month ago
There is a newer version of this series
drivers/net/phy/mscc/mscc_ptp.c | 16 +++++++---------
1 file changed, 7 insertions(+), 9 deletions(-)
[PATCH net v2] phy: mscc: Stop taking ts_lock for tx_queue and use its own lock
Posted by Horatiu Vultur 1 month ago 
When transmitting a PTP frame which is timestamp using 2 step, the
following warning appears if CONFIG_PROVE_LOCKING is enabled:
=============================
[ BUG: Invalid wait context ]
6.17.0-rc1-00326-ge6160462704e #427 Not tainted
-----------------------------
ptp4l/119 is trying to lock:
c2a44ed4 (&vsc8531->ts_lock){+.+.}-{3:3}, at: vsc85xx_txtstamp+0x50/0xac
other info that might help us debug this:
context-{4:4}
4 locks held by ptp4l/119:
 #0: c145f068 (rcu_read_lock_bh){....}-{1:2}, at: __dev_queue_xmit+0x58/0x1440
 #1: c29df974 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock){+...}-{2:2}, at: __dev_queue_xmit+0x5c4/0x1440
 #2: c2aaaad0 (_xmit_ETHER#2){+.-.}-{2:2}, at: sch_direct_xmit+0x108/0x350
 #3: c2aac170 (&lan966x->tx_lock){+.-.}-{2:2}, at: lan966x_port_xmit+0xd0/0x350
stack backtrace:
CPU: 0 UID: 0 PID: 119 Comm: ptp4l Not tainted 6.17.0-rc1-00326-ge6160462704e #427 NONE
Hardware name: Generic DT based system
Call trace:
 unwind_backtrace from show_stack+0x10/0x14
 show_stack from dump_stack_lvl+0x7c/0xac
 dump_stack_lvl from __lock_acquire+0x8e8/0x29dc
 __lock_acquire from lock_acquire+0x108/0x38c
 lock_acquire from __mutex_lock+0xb0/0xe78
 __mutex_lock from mutex_lock_nested+0x1c/0x24
 mutex_lock_nested from vsc85xx_txtstamp+0x50/0xac
 vsc85xx_txtstamp from lan966x_fdma_xmit+0xd8/0x3a8
 lan966x_fdma_xmit from lan966x_port_xmit+0x1bc/0x350
 lan966x_port_xmit from dev_hard_start_xmit+0xc8/0x2c0
 dev_hard_start_xmit from sch_direct_xmit+0x8c/0x350
 sch_direct_xmit from __dev_queue_xmit+0x680/0x1440
 __dev_queue_xmit from packet_sendmsg+0xfa4/0x1568
 packet_sendmsg from __sys_sendto+0x110/0x19c
 __sys_sendto from sys_send+0x18/0x20
 sys_send from ret_fast_syscall+0x0/0x1c
Exception stack(0xf0b05fa8 to 0xf0b05ff0)
5fa0:                   00000001 0000000e 0000000e 0004b47a 0000003a 00000000
5fc0: 00000001 0000000e 00000000 00000121 0004af58 00044874 00000000 00000000
5fe0: 00000001 bee9d420 00025a10 b6e75c7c

So, instead of using the ts_lock for tx_queue, use the spinlock that
skb_buff_head has.

Fixes: 7d272e63e0979d ("net: phy: mscc: timestamping and PHC support")
Signed-off-by: Horatiu Vultur <horatiu.vultur@microchip.com>

---
v1->v2:
- initialize tx_queue in ptp_probe
- purge the tx_queue when the driver is removed or when TX timestamping
  is OFF
---
 drivers/net/phy/mscc/mscc_ptp.c | 16 +++++++---------
 1 file changed, 7 insertions(+), 9 deletions(-)

diff --git a/drivers/net/phy/mscc/mscc_ptp.c b/drivers/net/phy/mscc/mscc_ptp.c
index 72847320cb652..e866a1d865f8b 100644
--- a/drivers/net/phy/mscc/mscc_ptp.c
+++ b/drivers/net/phy/mscc/mscc_ptp.c
@@ -461,7 +461,7 @@ static void vsc85xx_dequeue_skb(struct vsc85xx_ptp *ptp)
 		return;
 
 	while (len--) {
-		skb = __skb_dequeue(&ptp->tx_queue);
+		skb = skb_dequeue(&ptp->tx_queue);
 		if (!skb)
 			return;
 
@@ -486,7 +486,7 @@ static void vsc85xx_dequeue_skb(struct vsc85xx_ptp *ptp)
 		 * packet in the FIFO right now, reschedule it for later
 		 * packets.
 		 */
-		__skb_queue_tail(&ptp->tx_queue, skb);
+		skb_queue_tail(&ptp->tx_queue, skb);
 	}
 }
 
@@ -1068,6 +1068,7 @@ static int vsc85xx_hwtstamp(struct mii_timestamper *mii_ts,
 	case HWTSTAMP_TX_ON:
 		break;
 	case HWTSTAMP_TX_OFF:
+		skb_queue_purge(&vsc8531->ptp->tx_queue);
 		break;
 	default:
 		return -ERANGE;
@@ -1092,9 +1093,6 @@ static int vsc85xx_hwtstamp(struct mii_timestamper *mii_ts,
 
 	mutex_lock(&vsc8531->ts_lock);
 
-	__skb_queue_purge(&vsc8531->ptp->tx_queue);
-	__skb_queue_head_init(&vsc8531->ptp->tx_queue);
-
 	/* Disable predictor while configuring the 1588 block */
 	val = vsc85xx_ts_read_csr(phydev, PROCESSOR,
 				  MSCC_PHY_PTP_INGR_PREDICTOR);
@@ -1180,9 +1178,7 @@ static void vsc85xx_txtstamp(struct mii_timestamper *mii_ts,
 
 	skb_shinfo(skb)->tx_flags |= SKBTX_IN_PROGRESS;
 
-	mutex_lock(&vsc8531->ts_lock);
-	__skb_queue_tail(&vsc8531->ptp->tx_queue, skb);
-	mutex_unlock(&vsc8531->ts_lock);
+	skb_queue_tail(&vsc8531->ptp->tx_queue, skb);
 	return;
 
 out:
@@ -1548,6 +1544,7 @@ void vsc8584_ptp_deinit(struct phy_device *phydev)
 	if (vsc8531->ptp->ptp_clock) {
 		ptp_clock_unregister(vsc8531->ptp->ptp_clock);
 		skb_queue_purge(&vsc8531->rx_skbs_list);
+		skb_queue_purge(&vsc8531->ptp->tx_queue);
 	}
 }
 
@@ -1571,7 +1568,7 @@ irqreturn_t vsc8584_handle_ts_interrupt(struct phy_device *phydev)
 	if (rc & VSC85XX_1588_INT_FIFO_ADD) {
 		vsc85xx_get_tx_ts(priv->ptp);
 	} else if (rc & VSC85XX_1588_INT_FIFO_OVERFLOW) {
-		__skb_queue_purge(&priv->ptp->tx_queue);
+		skb_queue_purge(&priv->ptp->tx_queue);
 		vsc85xx_ts_reset_fifo(phydev);
 	}
 
@@ -1591,6 +1588,7 @@ int vsc8584_ptp_probe(struct phy_device *phydev)
 	mutex_init(&vsc8531->phc_lock);
 	mutex_init(&vsc8531->ts_lock);
 	skb_queue_head_init(&vsc8531->rx_skbs_list);
+	skb_queue_head_init(&vsc8531->ptp->tx_queue);
 
 	/* Retrieve the shared load/save GPIO. Request it as non exclusive as
 	 * the same GPIO can be requested by all the PHYs of the same package.
-- 
2.34.1
Re: [PATCH net v2] phy: mscc: Stop taking ts_lock for tx_queue and use its own lock
Posted by Vadim Fedorenko 1 month ago 
On 01/09/2025 10:23, Horatiu Vultur wrote:
> When transmitting a PTP frame which is timestamp using 2 step, the
> following warning appears if CONFIG_PROVE_LOCKING is enabled:
> =============================
> [ BUG: Invalid wait context ]
> 6.17.0-rc1-00326-ge6160462704e #427 Not tainted
> -----------------------------
> ptp4l/119 is trying to lock:
> c2a44ed4 (&vsc8531->ts_lock){+.+.}-{3:3}, at: vsc85xx_txtstamp+0x50/0xac
> other info that might help us debug this:
> context-{4:4}
> 4 locks held by ptp4l/119:
>   #0: c145f068 (rcu_read_lock_bh){....}-{1:2}, at: __dev_queue_xmit+0x58/0x1440
>   #1: c29df974 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock){+...}-{2:2}, at: __dev_queue_xmit+0x5c4/0x1440
>   #2: c2aaaad0 (_xmit_ETHER#2){+.-.}-{2:2}, at: sch_direct_xmit+0x108/0x350
>   #3: c2aac170 (&lan966x->tx_lock){+.-.}-{2:2}, at: lan966x_port_xmit+0xd0/0x350
> stack backtrace:
> CPU: 0 UID: 0 PID: 119 Comm: ptp4l Not tainted 6.17.0-rc1-00326-ge6160462704e #427 NONE
> Hardware name: Generic DT based system
> Call trace:
>   unwind_backtrace from show_stack+0x10/0x14
>   show_stack from dump_stack_lvl+0x7c/0xac
>   dump_stack_lvl from __lock_acquire+0x8e8/0x29dc
>   __lock_acquire from lock_acquire+0x108/0x38c
>   lock_acquire from __mutex_lock+0xb0/0xe78
>   __mutex_lock from mutex_lock_nested+0x1c/0x24
>   mutex_lock_nested from vsc85xx_txtstamp+0x50/0xac
>   vsc85xx_txtstamp from lan966x_fdma_xmit+0xd8/0x3a8
>   lan966x_fdma_xmit from lan966x_port_xmit+0x1bc/0x350
>   lan966x_port_xmit from dev_hard_start_xmit+0xc8/0x2c0
>   dev_hard_start_xmit from sch_direct_xmit+0x8c/0x350
>   sch_direct_xmit from __dev_queue_xmit+0x680/0x1440
>   __dev_queue_xmit from packet_sendmsg+0xfa4/0x1568
>   packet_sendmsg from __sys_sendto+0x110/0x19c
>   __sys_sendto from sys_send+0x18/0x20
>   sys_send from ret_fast_syscall+0x0/0x1c
> Exception stack(0xf0b05fa8 to 0xf0b05ff0)
> 5fa0:                   00000001 0000000e 0000000e 0004b47a 0000003a 00000000
> 5fc0: 00000001 0000000e 00000000 00000121 0004af58 00044874 00000000 00000000
> 5fe0: 00000001 bee9d420 00025a10 b6e75c7c
> 
> So, instead of using the ts_lock for tx_queue, use the spinlock that
> skb_buff_head has.
> 
> Fixes: 7d272e63e0979d ("net: phy: mscc: timestamping and PHC support")
> Signed-off-by: Horatiu Vultur <horatiu.vultur@microchip.com>
> 
> ---
> v1->v2:
> - initialize tx_queue in ptp_probe
> - purge the tx_queue when the driver is removed or when TX timestamping
>    is OFF
> ---
>   drivers/net/phy/mscc/mscc_ptp.c | 16 +++++++---------
>   1 file changed, 7 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/net/phy/mscc/mscc_ptp.c b/drivers/net/phy/mscc/mscc_ptp.c
> index 72847320cb652..e866a1d865f8b 100644
> --- a/drivers/net/phy/mscc/mscc_ptp.c
> +++ b/drivers/net/phy/mscc/mscc_ptp.c
> @@ -461,7 +461,7 @@ static void vsc85xx_dequeue_skb(struct vsc85xx_ptp *ptp)
>   		return;
>   
>   	while (len--) {
> -		skb = __skb_dequeue(&ptp->tx_queue);
> +		skb = skb_dequeue(&ptp->tx_queue);

Now as you switched to use spinlock of tx_queue, it is technically
correct to change skb_queue_len(&ptp->tx_queue) to
skb_queue_len_lockless(&ptp->tx_queue) a couple of lines above this
chunk.

Otherwise LGTM, once skb_queue_len fixed you can add

Reviewed-by: Vadim Fedorenko <vadim.fedorenko@linux.dev>


Thanks!

>   		if (!skb)
>   			return;
>   
> @@ -486,7 +486,7 @@ static void vsc85xx_dequeue_skb(struct vsc85xx_ptp *ptp)
>   		 * packet in the FIFO right now, reschedule it for later
>   		 * packets.
>   		 */
> -		__skb_queue_tail(&ptp->tx_queue, skb);
> +		skb_queue_tail(&ptp->tx_queue, skb);
Re: [PATCH net v2] phy: mscc: Stop taking ts_lock for tx_queue and use its own lock
Posted by Horatiu Vultur 1 month ago 
The 09/01/2025 11:19, Vadim Fedorenko wrote:

Hi Vadim,

> 
> On 01/09/2025 10:23, Horatiu Vultur wrote:
> > When transmitting a PTP frame which is timestamp using 2 step, the
> > following warning appears if CONFIG_PROVE_LOCKING is enabled:
> > =============================
> > [ BUG: Invalid wait context ]
> > 6.17.0-rc1-00326-ge6160462704e #427 Not tainted
> > -----------------------------
> > ptp4l/119 is trying to lock:
> > c2a44ed4 (&vsc8531->ts_lock){+.+.}-{3:3}, at: vsc85xx_txtstamp+0x50/0xac
> > other info that might help us debug this:
> > context-{4:4}
> > 4 locks held by ptp4l/119:
> >   #0: c145f068 (rcu_read_lock_bh){....}-{1:2}, at: __dev_queue_xmit+0x58/0x1440
> >   #1: c29df974 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock){+...}-{2:2}, at: __dev_queue_xmit+0x5c4/0x1440
> >   #2: c2aaaad0 (_xmit_ETHER#2){+.-.}-{2:2}, at: sch_direct_xmit+0x108/0x350
> >   #3: c2aac170 (&lan966x->tx_lock){+.-.}-{2:2}, at: lan966x_port_xmit+0xd0/0x350
> > stack backtrace:
> > CPU: 0 UID: 0 PID: 119 Comm: ptp4l Not tainted 6.17.0-rc1-00326-ge6160462704e #427 NONE
> > Hardware name: Generic DT based system
> > Call trace:
> >   unwind_backtrace from show_stack+0x10/0x14
> >   show_stack from dump_stack_lvl+0x7c/0xac
> >   dump_stack_lvl from __lock_acquire+0x8e8/0x29dc
> >   __lock_acquire from lock_acquire+0x108/0x38c
> >   lock_acquire from __mutex_lock+0xb0/0xe78
> >   __mutex_lock from mutex_lock_nested+0x1c/0x24
> >   mutex_lock_nested from vsc85xx_txtstamp+0x50/0xac
> >   vsc85xx_txtstamp from lan966x_fdma_xmit+0xd8/0x3a8
> >   lan966x_fdma_xmit from lan966x_port_xmit+0x1bc/0x350
> >   lan966x_port_xmit from dev_hard_start_xmit+0xc8/0x2c0
> >   dev_hard_start_xmit from sch_direct_xmit+0x8c/0x350
> >   sch_direct_xmit from __dev_queue_xmit+0x680/0x1440
> >   __dev_queue_xmit from packet_sendmsg+0xfa4/0x1568
> >   packet_sendmsg from __sys_sendto+0x110/0x19c
> >   __sys_sendto from sys_send+0x18/0x20
> >   sys_send from ret_fast_syscall+0x0/0x1c
> > Exception stack(0xf0b05fa8 to 0xf0b05ff0)
> > 5fa0:                   00000001 0000000e 0000000e 0004b47a 0000003a 00000000
> > 5fc0: 00000001 0000000e 00000000 00000121 0004af58 00044874 00000000 00000000
> > 5fe0: 00000001 bee9d420 00025a10 b6e75c7c
> > 
> > So, instead of using the ts_lock for tx_queue, use the spinlock that
> > skb_buff_head has.
> > 
> > Fixes: 7d272e63e0979d ("net: phy: mscc: timestamping and PHC support")
> > Signed-off-by: Horatiu Vultur <horatiu.vultur@microchip.com>
> > 
> > ---
> > v1->v2:
> > - initialize tx_queue in ptp_probe
> > - purge the tx_queue when the driver is removed or when TX timestamping
> >    is OFF
> > ---
> >   drivers/net/phy/mscc/mscc_ptp.c | 16 +++++++---------
> >   1 file changed, 7 insertions(+), 9 deletions(-)
> > 
> > diff --git a/drivers/net/phy/mscc/mscc_ptp.c b/drivers/net/phy/mscc/mscc_ptp.c
> > index 72847320cb652..e866a1d865f8b 100644
> > --- a/drivers/net/phy/mscc/mscc_ptp.c
> > +++ b/drivers/net/phy/mscc/mscc_ptp.c
> > @@ -461,7 +461,7 @@ static void vsc85xx_dequeue_skb(struct vsc85xx_ptp *ptp)
> >               return;
> > 
> >       while (len--) {
> > -             skb = __skb_dequeue(&ptp->tx_queue);
> > +             skb = skb_dequeue(&ptp->tx_queue);
> 
> Now as you switched to use spinlock of tx_queue, it is technically
> correct to change skb_queue_len(&ptp->tx_queue) to
> skb_queue_len_lockless(&ptp->tx_queue) a couple of lines above this
> chunk.

I will update this in the next version.
Thanks!

> 
> Otherwise LGTM, once skb_queue_len fixed you can add
> 
> Reviewed-by: Vadim Fedorenko <vadim.fedorenko@linux.dev>
> 
> 
> Thanks!
> 
> >               if (!skb)
> >                       return;
> > 
> > @@ -486,7 +486,7 @@ static void vsc85xx_dequeue_skb(struct vsc85xx_ptp *ptp)
> >                * packet in the FIFO right now, reschedule it for later
> >                * packets.
> >                */
> > -             __skb_queue_tail(&ptp->tx_queue, skb);
> > +             skb_queue_tail(&ptp->tx_queue, skb);
> 

-- 
/Horatiu

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