lpuart_dma_shutdown tears down lpuart dma, but lpuart_flush_buffer can
still occur which in turn tries to access dma apis if lpuart_dma_tx_use
flag is true. At this point since dma is torn down, these dma apis can
abort. Set lpuart_dma_tx_use and the corresponding rx flag
lpuart_dma_rx_use to false in lpuart_dma_shutdown so that dmas are not
accessed after they are relinquished.
Otherwise, when try to kill btattach, kernel may panic. This patch may
fix this issue.
root@imx8ulpevk:~# btattach -B /dev/ttyLP2 -S 115200
^C[ 90.182296] Internal error: synchronous external abort: 96000210 [#1] PREEMPT SMP
[ 90.189806] Modules linked in: moal(O) mlan(O)
[ 90.194258] CPU: 0 PID: 503 Comm: btattach Tainted: G O 5.15.32-06136-g34eecdf2f9e4 #37
[ 90.203554] Hardware name: NXP i.MX8ULP 9X9 EVK (DT)
[ 90.208513] pstate: 600000c5 (nZCv daIF -PAN -UAO -TCO -DIT -SSBS BTYPE=--)
[ 90.215470] pc : fsl_edma3_disable_request+0x8/0x60
[ 90.220358] lr : fsl_edma3_terminate_all+0x34/0x20c
[ 90.225237] sp : ffff800013f0bac0
[ 90.228548] x29: ffff800013f0bac0 x28: 0000000000000001 x27: ffff000008404800
[ 90.235681] x26: ffff000008404960 x25: ffff000008404a08 x24: ffff000008404a00
[ 90.242813] x23: ffff000008404a60 x22: 0000000000000002 x21: 0000000000000000
[ 90.249946] x20: ffff800013f0baf8 x19: ffff00000559c800 x18: 0000000000000000
[ 90.257078] x17: 0000000000000000 x16: 0000000000000000 x15: 0000000000000000
[ 90.264211] x14: 0000000000000003 x13: 0000000000000000 x12: 0000000000000040
[ 90.271344] x11: ffff00000600c248 x10: ffff800013f0bb10 x9 : ffff000057bcb090
[ 90.278477] x8 : fffffc0000241a08 x7 : ffff00000534ee00 x6 : ffff000008404804
[ 90.285609] x5 : 0000000000000000 x4 : 0000000000000000 x3 : ffff0000055b3480
[ 90.292742] x2 : ffff8000135c0000 x1 : ffff00000534ee00 x0 : ffff00000559c800
[ 90.299876] Call trace:
[ 90.302321] fsl_edma3_disable_request+0x8/0x60
[ 90.306851] lpuart_flush_buffer+0x40/0x160
[ 90.311037] uart_flush_buffer+0x88/0x120
[ 90.315050] tty_driver_flush_buffer+0x20/0x30
[ 90.319496] hci_uart_flush+0x44/0x90
[ 90.323162] +0x34/0x12c
[ 90.327253] tty_ldisc_close+0x38/0x70
[ 90.331005] tty_ldisc_release+0xa8/0x190
[ 90.335018] tty_release_struct+0x24/0x8c
[ 90.339022] tty_release+0x3ec/0x4c0
[ 90.342593] __fput+0x70/0x234
[ 90.345652] ____fput+0x14/0x20
[ 90.348790] task_work_run+0x84/0x17c
[ 90.352455] do_exit+0x310/0x96c
[ 90.355688] do_group_exit+0x3c/0xa0
[ 90.359259] __arm64_sys_exit_group+0x1c/0x20
[ 90.363609] invoke_syscall+0x48/0x114
[ 90.367362] el0_svc_common.constprop.0+0xd4/0xfc
[ 90.372068] do_el0_svc+0x2c/0x94
[ 90.375379] el0_svc+0x28/0x80
[ 90.378438] el0t_64_sync_handler+0xa8/0x130
[ 90.382711] el0t_64_sync+0x1a0/0x1a4
[ 90.386376] Code: 17ffffda d503201f d503233f f9409802 (b9400041)
[ 90.392467] ---[ end trace 2f60524b4a43f1f6 ]---
[ 90.397073] note: btattach[503] exited with preempt_count 1
[ 90.402636] Fixing recursive fault but reboot is needed!
Fixes: 6250cc30c4c4 ("tty: serial: fsl_lpuart: Use scatter/gather DMA for Tx")
Signed-off-by: Thara Gopinath <[email protected]>
Signed-off-by: Sherry Sun <[email protected]>
---
drivers/tty/serial/fsl_lpuart.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/drivers/tty/serial/fsl_lpuart.c b/drivers/tty/serial/fsl_lpuart.c
index f21915015d67..064bd1f33c21 100644
--- a/drivers/tty/serial/fsl_lpuart.c
+++ b/drivers/tty/serial/fsl_lpuart.c
@@ -1771,6 +1771,7 @@ static void lpuart_dma_shutdown(struct lpuart_port *sport)
if (sport->lpuart_dma_rx_use) {
del_timer_sync(&sport->lpuart_timer);
lpuart_dma_rx_free(&sport->port);
+ sport->lpuart_dma_rx_use = false;
}
if (sport->lpuart_dma_tx_use) {
@@ -1779,6 +1780,7 @@ static void lpuart_dma_shutdown(struct lpuart_port *sport)
sport->dma_tx_in_progress = false;
dmaengine_terminate_all(sport->dma_tx_chan);
}
+ sport->lpuart_dma_tx_use = false;
}
if (sport->dma_tx_chan)
--
2.17.1
On Tue, 20 Sep 2022, Sherry Sun wrote:
> lpuart_dma_shutdown tears down lpuart dma, but lpuart_flush_buffer can
> still occur which in turn tries to access dma apis if lpuart_dma_tx_use
> flag is true. At this point since dma is torn down, these dma apis can
> abort. Set lpuart_dma_tx_use and the corresponding rx flag
> lpuart_dma_rx_use to false in lpuart_dma_shutdown so that dmas are not
> accessed after they are relinquished.
>
> Otherwise, when try to kill btattach, kernel may panic. This patch may
> fix this issue.
> root@imx8ulpevk:~# btattach -B /dev/ttyLP2 -S 115200
> ^C[ 90.182296] Internal error: synchronous external abort: 96000210 [#1] PREEMPT SMP
> [ 90.189806] Modules linked in: moal(O) mlan(O)
> [ 90.194258] CPU: 0 PID: 503 Comm: btattach Tainted: G O 5.15.32-06136-g34eecdf2f9e4 #37
> [ 90.203554] Hardware name: NXP i.MX8ULP 9X9 EVK (DT)
> [ 90.208513] pstate: 600000c5 (nZCv daIF -PAN -UAO -TCO -DIT -SSBS BTYPE=--)
> [ 90.215470] pc : fsl_edma3_disable_request+0x8/0x60
> [ 90.220358] lr : fsl_edma3_terminate_all+0x34/0x20c
> [ 90.225237] sp : ffff800013f0bac0
> [ 90.228548] x29: ffff800013f0bac0 x28: 0000000000000001 x27: ffff000008404800
> [ 90.235681] x26: ffff000008404960 x25: ffff000008404a08 x24: ffff000008404a00
> [ 90.242813] x23: ffff000008404a60 x22: 0000000000000002 x21: 0000000000000000
> [ 90.249946] x20: ffff800013f0baf8 x19: ffff00000559c800 x18: 0000000000000000
> [ 90.257078] x17: 0000000000000000 x16: 0000000000000000 x15: 0000000000000000
> [ 90.264211] x14: 0000000000000003 x13: 0000000000000000 x12: 0000000000000040
> [ 90.271344] x11: ffff00000600c248 x10: ffff800013f0bb10 x9 : ffff000057bcb090
> [ 90.278477] x8 : fffffc0000241a08 x7 : ffff00000534ee00 x6 : ffff000008404804
> [ 90.285609] x5 : 0000000000000000 x4 : 0000000000000000 x3 : ffff0000055b3480
> [ 90.292742] x2 : ffff8000135c0000 x1 : ffff00000534ee00 x0 : ffff00000559c800
> [ 90.299876] Call trace:
> [ 90.302321] fsl_edma3_disable_request+0x8/0x60
> [ 90.306851] lpuart_flush_buffer+0x40/0x160
> [ 90.311037] uart_flush_buffer+0x88/0x120
> [ 90.315050] tty_driver_flush_buffer+0x20/0x30
> [ 90.319496] hci_uart_flush+0x44/0x90
> [ 90.323162] +0x34/0x12c
> [ 90.327253] tty_ldisc_close+0x38/0x70
> [ 90.331005] tty_ldisc_release+0xa8/0x190
> [ 90.335018] tty_release_struct+0x24/0x8c
> [ 90.339022] tty_release+0x3ec/0x4c0
> [ 90.342593] __fput+0x70/0x234
> [ 90.345652] ____fput+0x14/0x20
> [ 90.348790] task_work_run+0x84/0x17c
> [ 90.352455] do_exit+0x310/0x96c
> [ 90.355688] do_group_exit+0x3c/0xa0
> [ 90.359259] __arm64_sys_exit_group+0x1c/0x20
> [ 90.363609] invoke_syscall+0x48/0x114
> [ 90.367362] el0_svc_common.constprop.0+0xd4/0xfc
> [ 90.372068] do_el0_svc+0x2c/0x94
> [ 90.375379] el0_svc+0x28/0x80
> [ 90.378438] el0t_64_sync_handler+0xa8/0x130
> [ 90.382711] el0t_64_sync+0x1a0/0x1a4
> [ 90.386376] Code: 17ffffda d503201f d503233f f9409802 (b9400041)
> [ 90.392467] ---[ end trace 2f60524b4a43f1f6 ]---
> [ 90.397073] note: btattach[503] exited with preempt_count 1
> [ 90.402636] Fixing recursive fault but reboot is needed!
>
> Fixes: 6250cc30c4c4 ("tty: serial: fsl_lpuart: Use scatter/gather DMA for Tx")
> Signed-off-by: Thara Gopinath <[email protected]>
> Signed-off-by: Sherry Sun <[email protected]>
> ---
> drivers/tty/serial/fsl_lpuart.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/drivers/tty/serial/fsl_lpuart.c b/drivers/tty/serial/fsl_lpuart.c
> index f21915015d67..064bd1f33c21 100644
> --- a/drivers/tty/serial/fsl_lpuart.c
> +++ b/drivers/tty/serial/fsl_lpuart.c
> @@ -1771,6 +1771,7 @@ static void lpuart_dma_shutdown(struct lpuart_port *sport)
> if (sport->lpuart_dma_rx_use) {
> del_timer_sync(&sport->lpuart_timer);
> lpuart_dma_rx_free(&sport->port);
> + sport->lpuart_dma_rx_use = false;
> }
>
> if (sport->lpuart_dma_tx_use) {
> @@ -1779,6 +1780,7 @@ static void lpuart_dma_shutdown(struct lpuart_port *sport)
> sport->dma_tx_in_progress = false;
> dmaengine_terminate_all(sport->dma_tx_chan);
> }
> + sport->lpuart_dma_tx_use = false;
> }
>
> if (sport->dma_tx_chan)
Isn't it still racy because lpuart_dma_shutdown() is called outside of
port's lock?
--
i.
> -----Original Message-----
> From: Ilpo Järvinen <[email protected]>
> Sent: 2022年9月20日 20:26
> To: Sherry Sun <[email protected]>
> Cc: [email protected]; [email protected];
> [email protected]; [email protected]; linux-
> [email protected]; dl-linux-imx <[email protected]>
> Subject: Re: [PATCH] tty: serial: fsl_lpuart: disable dma rx/tx use flags in
> lpuart_dma_shutdown
>
> On Tue, 20 Sep 2022, Sherry Sun wrote:
>
> > lpuart_dma_shutdown tears down lpuart dma, but lpuart_flush_buffer can
> > still occur which in turn tries to access dma apis if
> > lpuart_dma_tx_use flag is true. At this point since dma is torn down,
> > these dma apis can abort. Set lpuart_dma_tx_use and the corresponding
> > rx flag lpuart_dma_rx_use to false in lpuart_dma_shutdown so that dmas
> > are not accessed after they are relinquished.
> >
> > Otherwise, when try to kill btattach, kernel may panic. This patch may
> > fix this issue.
> > root@imx8ulpevk:~# btattach -B /dev/ttyLP2 -S 115200
> > ^C[ 90.182296] Internal error: synchronous external abort: 96000210 [#1]
> PREEMPT SMP
> > [ 90.189806] Modules linked in: moal(O) mlan(O)
> > [ 90.194258] CPU: 0 PID: 503 Comm: btattach Tainted: G O
> 5.15.32-06136-g34eecdf2f9e4 #37
> > [ 90.203554] Hardware name: NXP i.MX8ULP 9X9 EVK (DT)
> > [ 90.208513] pstate: 600000c5 (nZCv daIF -PAN -UAO -TCO -DIT -SSBS
> BTYPE=--)
> > [ 90.215470] pc : fsl_edma3_disable_request+0x8/0x60
> > [ 90.220358] lr : fsl_edma3_terminate_all+0x34/0x20c
> > [ 90.225237] sp : ffff800013f0bac0
> > [ 90.228548] x29: ffff800013f0bac0 x28: 0000000000000001 x27:
> ffff000008404800
> > [ 90.235681] x26: ffff000008404960 x25: ffff000008404a08 x24:
> ffff000008404a00
> > [ 90.242813] x23: ffff000008404a60 x22: 0000000000000002 x21:
> 0000000000000000
> > [ 90.249946] x20: ffff800013f0baf8 x19: ffff00000559c800 x18:
> 0000000000000000
> > [ 90.257078] x17: 0000000000000000 x16: 0000000000000000 x15:
> 0000000000000000
> > [ 90.264211] x14: 0000000000000003 x13: 0000000000000000 x12:
> 0000000000000040
> > [ 90.271344] x11: ffff00000600c248 x10: ffff800013f0bb10 x9 :
> ffff000057bcb090
> > [ 90.278477] x8 : fffffc0000241a08 x7 : ffff00000534ee00 x6 :
> ffff000008404804
> > [ 90.285609] x5 : 0000000000000000 x4 : 0000000000000000 x3 :
> ffff0000055b3480
> > [ 90.292742] x2 : ffff8000135c0000 x1 : ffff00000534ee00 x0 :
> ffff00000559c800
> > [ 90.299876] Call trace:
> > [ 90.302321] fsl_edma3_disable_request+0x8/0x60
> > [ 90.306851] lpuart_flush_buffer+0x40/0x160
> > [ 90.311037] uart_flush_buffer+0x88/0x120
> > [ 90.315050] tty_driver_flush_buffer+0x20/0x30
> > [ 90.319496] hci_uart_flush+0x44/0x90
> > [ 90.323162] +0x34/0x12c
> > [ 90.327253] tty_ldisc_close+0x38/0x70
> > [ 90.331005] tty_ldisc_release+0xa8/0x190
> > [ 90.335018] tty_release_struct+0x24/0x8c
> > [ 90.339022] tty_release+0x3ec/0x4c0
> > [ 90.342593] __fput+0x70/0x234
> > [ 90.345652] ____fput+0x14/0x20
> > [ 90.348790] task_work_run+0x84/0x17c
> > [ 90.352455] do_exit+0x310/0x96c
> > [ 90.355688] do_group_exit+0x3c/0xa0
> > [ 90.359259] __arm64_sys_exit_group+0x1c/0x20
> > [ 90.363609] invoke_syscall+0x48/0x114
> > [ 90.367362] el0_svc_common.constprop.0+0xd4/0xfc
> > [ 90.372068] do_el0_svc+0x2c/0x94
> > [ 90.375379] el0_svc+0x28/0x80
> > [ 90.378438] el0t_64_sync_handler+0xa8/0x130
> > [ 90.382711] el0t_64_sync+0x1a0/0x1a4
> > [ 90.386376] Code: 17ffffda d503201f d503233f f9409802 (b9400041)
> > [ 90.392467] ---[ end trace 2f60524b4a43f1f6 ]---
> > [ 90.397073] note: btattach[503] exited with preempt_count 1
> > [ 90.402636] Fixing recursive fault but reboot is needed!
> >
> > Fixes: 6250cc30c4c4 ("tty: serial: fsl_lpuart: Use scatter/gather DMA
> > for Tx")
> > Signed-off-by: Thara Gopinath <[email protected]>
> > Signed-off-by: Sherry Sun <[email protected]>
> > ---
> > drivers/tty/serial/fsl_lpuart.c | 2 ++
> > 1 file changed, 2 insertions(+)
> >
> > diff --git a/drivers/tty/serial/fsl_lpuart.c
> > b/drivers/tty/serial/fsl_lpuart.c index f21915015d67..064bd1f33c21
> > 100644
> > --- a/drivers/tty/serial/fsl_lpuart.c
> > +++ b/drivers/tty/serial/fsl_lpuart.c
> > @@ -1771,6 +1771,7 @@ static void lpuart_dma_shutdown(struct
> lpuart_port *sport)
> > if (sport->lpuart_dma_rx_use) {
> > del_timer_sync(&sport->lpuart_timer);
> > lpuart_dma_rx_free(&sport->port);
> > + sport->lpuart_dma_rx_use = false;
> > }
> >
> > if (sport->lpuart_dma_tx_use) {
> > @@ -1779,6 +1780,7 @@ static void lpuart_dma_shutdown(struct
> lpuart_port *sport)
> > sport->dma_tx_in_progress = false;
> > dmaengine_terminate_all(sport->dma_tx_chan);
> > }
> > + sport->lpuart_dma_tx_use = false;
> > }
> >
> > if (sport->dma_tx_chan)
>
> Isn't it still racy because lpuart_dma_shutdown() is called outside of port's
> lock?
Hi Ilpo, do you think add the following changes should work for this?
diff --git a/drivers/tty/serial/fsl_lpuart.c b/drivers/tty/serial/fsl_lpuart.c
index 064bd1f33c21..b3c53935fbc8 100644
--- a/drivers/tty/serial/fsl_lpuart.c
+++ b/drivers/tty/serial/fsl_lpuart.c
@@ -1768,10 +1768,14 @@ static int lpuart32_startup(struct uart_port *port)
static void lpuart_dma_shutdown(struct lpuart_port *sport)
{
+ unsigned long flags;
+
if (sport->lpuart_dma_rx_use) {
del_timer_sync(&sport->lpuart_timer);
lpuart_dma_rx_free(&sport->port);
+ spin_lock_irqsave(&sport->port.lock, flags);
sport->lpuart_dma_rx_use = false;
+ spin_unlock_irqrestore(&sport->port.lock, flags);
}
if (sport->lpuart_dma_tx_use) {
@@ -1780,7 +1784,9 @@ static void lpuart_dma_shutdown(struct lpuart_port *sport)
sport->dma_tx_in_progress = false;
dmaengine_terminate_all(sport->dma_tx_chan);
}
+ spin_lock_irqsave(&sport->port.lock, flags);
sport->lpuart_dma_tx_use = false;
+ spin_unlock_irqrestore(&sport->port.lock, flags);
}
Best Regards
Sherry
On Tue, 20 Sep 2022, Sherry Sun wrote:
> lpuart_dma_shutdown tears down lpuart dma, but lpuart_flush_buffer can
> still occur which in turn tries to access dma apis if lpuart_dma_tx_use
> flag is true. At this point since dma is torn down, these dma apis can
> abort. Set lpuart_dma_tx_use and the corresponding rx flag
> lpuart_dma_rx_use to false in lpuart_dma_shutdown so that dmas are not
> accessed after they are relinquished.
>
> Otherwise, when try to kill btattach, kernel may panic. This patch may
> fix this issue.
> root@imx8ulpevk:~# btattach -B /dev/ttyLP2 -S 115200
> ^C[ 90.182296] Internal error: synchronous external abort: 96000210 [#1] PREEMPT SMP
> [ 90.189806] Modules linked in: moal(O) mlan(O)
> [ 90.194258] CPU: 0 PID: 503 Comm: btattach Tainted: G O 5.15.32-06136-g34eecdf2f9e4 #37
> [ 90.203554] Hardware name: NXP i.MX8ULP 9X9 EVK (DT)
> [ 90.208513] pstate: 600000c5 (nZCv daIF -PAN -UAO -TCO -DIT -SSBS BTYPE=--)
> [ 90.215470] pc : fsl_edma3_disable_request+0x8/0x60
> [ 90.220358] lr : fsl_edma3_terminate_all+0x34/0x20c
> [ 90.225237] sp : ffff800013f0bac0
> [ 90.228548] x29: ffff800013f0bac0 x28: 0000000000000001 x27: ffff000008404800
> [ 90.235681] x26: ffff000008404960 x25: ffff000008404a08 x24: ffff000008404a00
> [ 90.242813] x23: ffff000008404a60 x22: 0000000000000002 x21: 0000000000000000
> [ 90.249946] x20: ffff800013f0baf8 x19: ffff00000559c800 x18: 0000000000000000
> [ 90.257078] x17: 0000000000000000 x16: 0000000000000000 x15: 0000000000000000
> [ 90.264211] x14: 0000000000000003 x13: 0000000000000000 x12: 0000000000000040
> [ 90.271344] x11: ffff00000600c248 x10: ffff800013f0bb10 x9 : ffff000057bcb090
> [ 90.278477] x8 : fffffc0000241a08 x7 : ffff00000534ee00 x6 : ffff000008404804
> [ 90.285609] x5 : 0000000000000000 x4 : 0000000000000000 x3 : ffff0000055b3480
> [ 90.292742] x2 : ffff8000135c0000 x1 : ffff00000534ee00 x0 : ffff00000559c800
> [ 90.299876] Call trace:
> [ 90.302321] fsl_edma3_disable_request+0x8/0x60
> [ 90.306851] lpuart_flush_buffer+0x40/0x160
> [ 90.311037] uart_flush_buffer+0x88/0x120
> [ 90.315050] tty_driver_flush_buffer+0x20/0x30
> [ 90.319496] hci_uart_flush+0x44/0x90
> [ 90.323162] +0x34/0x12c
> [ 90.327253] tty_ldisc_close+0x38/0x70
> [ 90.331005] tty_ldisc_release+0xa8/0x190
> [ 90.335018] tty_release_struct+0x24/0x8c
> [ 90.339022] tty_release+0x3ec/0x4c0
> [ 90.342593] __fput+0x70/0x234
> [ 90.345652] ____fput+0x14/0x20
> [ 90.348790] task_work_run+0x84/0x17c
> [ 90.352455] do_exit+0x310/0x96c
> [ 90.355688] do_group_exit+0x3c/0xa0
> [ 90.359259] __arm64_sys_exit_group+0x1c/0x20
> [ 90.363609] invoke_syscall+0x48/0x114
> [ 90.367362] el0_svc_common.constprop.0+0xd4/0xfc
> [ 90.372068] do_el0_svc+0x2c/0x94
> [ 90.375379] el0_svc+0x28/0x80
> [ 90.378438] el0t_64_sync_handler+0xa8/0x130
> [ 90.382711] el0t_64_sync+0x1a0/0x1a4
> [ 90.386376] Code: 17ffffda d503201f d503233f f9409802 (b9400041)
> [ 90.392467] ---[ end trace 2f60524b4a43f1f6 ]---
> [ 90.397073] note: btattach[503] exited with preempt_count 1
> [ 90.402636] Fixing recursive fault but reboot is needed!
>
> Fixes: 6250cc30c4c4 ("tty: serial: fsl_lpuart: Use scatter/gather DMA for Tx")
> Signed-off-by: Thara Gopinath <[email protected]>
> Signed-off-by: Sherry Sun <[email protected]>
> ---
> drivers/tty/serial/fsl_lpuart.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/drivers/tty/serial/fsl_lpuart.c b/drivers/tty/serial/fsl_lpuart.c
> index f21915015d67..064bd1f33c21 100644
> --- a/drivers/tty/serial/fsl_lpuart.c
> +++ b/drivers/tty/serial/fsl_lpuart.c
> @@ -1771,6 +1771,7 @@ static void lpuart_dma_shutdown(struct lpuart_port *sport)
> if (sport->lpuart_dma_rx_use) {
> del_timer_sync(&sport->lpuart_timer);
> lpuart_dma_rx_free(&sport->port);
> + sport->lpuart_dma_rx_use = false;
> }
>
> if (sport->lpuart_dma_tx_use) {
> @@ -1779,6 +1780,7 @@ static void lpuart_dma_shutdown(struct lpuart_port *sport)
> sport->dma_tx_in_progress = false;
> dmaengine_terminate_all(sport->dma_tx_chan);
> }
> + sport->lpuart_dma_tx_use = false;
> }
>
> if (sport->dma_tx_chan)
Reviewed-by: Ilpo J?rvinen <[email protected]>
--
i.
On Tue, 20 Sep 2022, Sherry Sun wrote:
>
>
> > -----Original Message-----
> > From: Ilpo Järvinen <[email protected]>
> > Sent: 2022年9月20日 20:26
> > To: Sherry Sun <[email protected]>
> > Cc: [email protected]; [email protected];
> > [email protected]; [email protected]; linux-
> > [email protected]; dl-linux-imx <[email protected]>
> > Subject: Re: [PATCH] tty: serial: fsl_lpuart: disable dma rx/tx use flags in
> > lpuart_dma_shutdown
> >
> > On Tue, 20 Sep 2022, Sherry Sun wrote:
> >
> > > lpuart_dma_shutdown tears down lpuart dma, but lpuart_flush_buffer can
> > > still occur which in turn tries to access dma apis if
> > > lpuart_dma_tx_use flag is true. At this point since dma is torn down,
> > > these dma apis can abort. Set lpuart_dma_tx_use and the corresponding
> > > rx flag lpuart_dma_rx_use to false in lpuart_dma_shutdown so that dmas
> > > are not accessed after they are relinquished.
> > >
> > > Otherwise, when try to kill btattach, kernel may panic. This patch may
> > > fix this issue.
> > > root@imx8ulpevk:~# btattach -B /dev/ttyLP2 -S 115200
> > > ^C[ 90.182296] Internal error: synchronous external abort: 96000210 [#1]
> > PREEMPT SMP
> > > [ 90.189806] Modules linked in: moal(O) mlan(O)
> > > [ 90.194258] CPU: 0 PID: 503 Comm: btattach Tainted: G O
> > 5.15.32-06136-g34eecdf2f9e4 #37
> > > [ 90.203554] Hardware name: NXP i.MX8ULP 9X9 EVK (DT)
> > > [ 90.208513] pstate: 600000c5 (nZCv daIF -PAN -UAO -TCO -DIT -SSBS
> > BTYPE=--)
> > > [ 90.215470] pc : fsl_edma3_disable_request+0x8/0x60
> > > [ 90.220358] lr : fsl_edma3_terminate_all+0x34/0x20c
> > > [ 90.225237] sp : ffff800013f0bac0
> > > [ 90.228548] x29: ffff800013f0bac0 x28: 0000000000000001 x27:
> > ffff000008404800
> > > [ 90.235681] x26: ffff000008404960 x25: ffff000008404a08 x24:
> > ffff000008404a00
> > > [ 90.242813] x23: ffff000008404a60 x22: 0000000000000002 x21:
> > 0000000000000000
> > > [ 90.249946] x20: ffff800013f0baf8 x19: ffff00000559c800 x18:
> > 0000000000000000
> > > [ 90.257078] x17: 0000000000000000 x16: 0000000000000000 x15:
> > 0000000000000000
> > > [ 90.264211] x14: 0000000000000003 x13: 0000000000000000 x12:
> > 0000000000000040
> > > [ 90.271344] x11: ffff00000600c248 x10: ffff800013f0bb10 x9 :
> > ffff000057bcb090
> > > [ 90.278477] x8 : fffffc0000241a08 x7 : ffff00000534ee00 x6 :
> > ffff000008404804
> > > [ 90.285609] x5 : 0000000000000000 x4 : 0000000000000000 x3 :
> > ffff0000055b3480
> > > [ 90.292742] x2 : ffff8000135c0000 x1 : ffff00000534ee00 x0 :
> > ffff00000559c800
> > > [ 90.299876] Call trace:
> > > [ 90.302321] fsl_edma3_disable_request+0x8/0x60
> > > [ 90.306851] lpuart_flush_buffer+0x40/0x160
> > > [ 90.311037] uart_flush_buffer+0x88/0x120
> > > [ 90.315050] tty_driver_flush_buffer+0x20/0x30
> > > [ 90.319496] hci_uart_flush+0x44/0x90
> > > [ 90.323162] +0x34/0x12c
> > > [ 90.327253] tty_ldisc_close+0x38/0x70
> > > [ 90.331005] tty_ldisc_release+0xa8/0x190
> > > [ 90.335018] tty_release_struct+0x24/0x8c
> > > [ 90.339022] tty_release+0x3ec/0x4c0
> > > [ 90.342593] __fput+0x70/0x234
> > > [ 90.345652] ____fput+0x14/0x20
> > > [ 90.348790] task_work_run+0x84/0x17c
> > > [ 90.352455] do_exit+0x310/0x96c
> > > [ 90.355688] do_group_exit+0x3c/0xa0
> > > [ 90.359259] __arm64_sys_exit_group+0x1c/0x20
> > > [ 90.363609] invoke_syscall+0x48/0x114
> > > [ 90.367362] el0_svc_common.constprop.0+0xd4/0xfc
> > > [ 90.372068] do_el0_svc+0x2c/0x94
> > > [ 90.375379] el0_svc+0x28/0x80
> > > [ 90.378438] el0t_64_sync_handler+0xa8/0x130
> > > [ 90.382711] el0t_64_sync+0x1a0/0x1a4
> > > [ 90.386376] Code: 17ffffda d503201f d503233f f9409802 (b9400041)
> > > [ 90.392467] ---[ end trace 2f60524b4a43f1f6 ]---
> > > [ 90.397073] note: btattach[503] exited with preempt_count 1
> > > [ 90.402636] Fixing recursive fault but reboot is needed!
> > >
> > > Fixes: 6250cc30c4c4 ("tty: serial: fsl_lpuart: Use scatter/gather DMA
> > > for Tx")
> > > Signed-off-by: Thara Gopinath <[email protected]>
> > > Signed-off-by: Sherry Sun <[email protected]>
> > > ---
> > > drivers/tty/serial/fsl_lpuart.c | 2 ++
> > > 1 file changed, 2 insertions(+)
> > >
> > > diff --git a/drivers/tty/serial/fsl_lpuart.c
> > > b/drivers/tty/serial/fsl_lpuart.c index f21915015d67..064bd1f33c21
> > > 100644
> > > --- a/drivers/tty/serial/fsl_lpuart.c
> > > +++ b/drivers/tty/serial/fsl_lpuart.c
> > > @@ -1771,6 +1771,7 @@ static void lpuart_dma_shutdown(struct
> > lpuart_port *sport)
> > > if (sport->lpuart_dma_rx_use) {
> > > del_timer_sync(&sport->lpuart_timer);
> > > lpuart_dma_rx_free(&sport->port);
> > > + sport->lpuart_dma_rx_use = false;
> > > }
> > >
> > > if (sport->lpuart_dma_tx_use) {
> > > @@ -1779,6 +1780,7 @@ static void lpuart_dma_shutdown(struct
> > lpuart_port *sport)
> > > sport->dma_tx_in_progress = false;
> > > dmaengine_terminate_all(sport->dma_tx_chan);
> > > }
> > > + sport->lpuart_dma_tx_use = false;
> > > }
> > >
> > > if (sport->dma_tx_chan)
> >
> > Isn't it still racy because lpuart_dma_shutdown() is called outside of port's
> > lock?
>
> Hi Ilpo, do you think add the following changes should work for this?
>
> diff --git a/drivers/tty/serial/fsl_lpuart.c b/drivers/tty/serial/fsl_lpuart.c
> index 064bd1f33c21..b3c53935fbc8 100644
> --- a/drivers/tty/serial/fsl_lpuart.c
> +++ b/drivers/tty/serial/fsl_lpuart.c
> @@ -1768,10 +1768,14 @@ static int lpuart32_startup(struct uart_port *port)
>
> static void lpuart_dma_shutdown(struct lpuart_port *sport)
> {
> + unsigned long flags;
> +
> if (sport->lpuart_dma_rx_use) {
> del_timer_sync(&sport->lpuart_timer);
> lpuart_dma_rx_free(&sport->port);
> + spin_lock_irqsave(&sport->port.lock, flags);
> sport->lpuart_dma_rx_use = false;
> + spin_unlock_irqrestore(&sport->port.lock, flags);
> }
>
> if (sport->lpuart_dma_tx_use) {
> @@ -1780,7 +1784,9 @@ static void lpuart_dma_shutdown(struct lpuart_port *sport)
> sport->dma_tx_in_progress = false;
> dmaengine_terminate_all(sport->dma_tx_chan);
> }
> + spin_lock_irqsave(&sport->port.lock, flags);
> sport->lpuart_dma_tx_use = false;
> + spin_unlock_irqrestore(&sport->port.lock, flags);
> }
After reading a bit more, I think the original patch is likely fine since
shutdown doesn't seem to be racing with flush_buffer.
--
i.
> > >
> > > On Tue, 20 Sep 2022, Sherry Sun wrote:
> > >
> > > > lpuart_dma_shutdown tears down lpuart dma, but lpuart_flush_buffer
> > > > can still occur which in turn tries to access dma apis if
> > > > lpuart_dma_tx_use flag is true. At this point since dma is torn
> > > > down, these dma apis can abort. Set lpuart_dma_tx_use and the
> > > > corresponding rx flag lpuart_dma_rx_use to false in
> > > > lpuart_dma_shutdown so that dmas are not accessed after they are
> relinquished.
> > > >
> > > > Otherwise, when try to kill btattach, kernel may panic. This patch
> > > > may fix this issue.
> > > > root@imx8ulpevk:~# btattach -B /dev/ttyLP2 -S 115200
> > > > ^C[ 90.182296] Internal error: synchronous external abort: 96000210
> [#1]
> > > PREEMPT SMP
> > > > [ 90.189806] Modules linked in: moal(O) mlan(O)
> > > > [ 90.194258] CPU: 0 PID: 503 Comm: btattach Tainted: G O
> > > 5.15.32-06136-g34eecdf2f9e4 #37
> > > > [ 90.203554] Hardware name: NXP i.MX8ULP 9X9 EVK (DT)
> > > > [ 90.208513] pstate: 600000c5 (nZCv daIF -PAN -UAO -TCO -DIT -SSBS
> > > BTYPE=--)
> > > > [ 90.215470] pc : fsl_edma3_disable_request+0x8/0x60
> > > > [ 90.220358] lr : fsl_edma3_terminate_all+0x34/0x20c
> > > > [ 90.225237] sp : ffff800013f0bac0
> > > > [ 90.228548] x29: ffff800013f0bac0 x28: 0000000000000001 x27:
> > > ffff000008404800
> > > > [ 90.235681] x26: ffff000008404960 x25: ffff000008404a08 x24:
> > > ffff000008404a00
> > > > [ 90.242813] x23: ffff000008404a60 x22: 0000000000000002 x21:
> > > 0000000000000000
> > > > [ 90.249946] x20: ffff800013f0baf8 x19: ffff00000559c800 x18:
> > > 0000000000000000
> > > > [ 90.257078] x17: 0000000000000000 x16: 0000000000000000 x15:
> > > 0000000000000000
> > > > [ 90.264211] x14: 0000000000000003 x13: 0000000000000000 x12:
> > > 0000000000000040
> > > > [ 90.271344] x11: ffff00000600c248 x10: ffff800013f0bb10 x9 :
> > > ffff000057bcb090
> > > > [ 90.278477] x8 : fffffc0000241a08 x7 : ffff00000534ee00 x6 :
> > > ffff000008404804
> > > > [ 90.285609] x5 : 0000000000000000 x4 : 0000000000000000 x3 :
> > > ffff0000055b3480
> > > > [ 90.292742] x2 : ffff8000135c0000 x1 : ffff00000534ee00 x0 :
> > > ffff00000559c800
> > > > [ 90.299876] Call trace:
> > > > [ 90.302321] fsl_edma3_disable_request+0x8/0x60
> > > > [ 90.306851] lpuart_flush_buffer+0x40/0x160
> > > > [ 90.311037] uart_flush_buffer+0x88/0x120
> > > > [ 90.315050] tty_driver_flush_buffer+0x20/0x30
> > > > [ 90.319496] hci_uart_flush+0x44/0x90
> > > > [ 90.323162] +0x34/0x12c
> > > > [ 90.327253] tty_ldisc_close+0x38/0x70
> > > > [ 90.331005] tty_ldisc_release+0xa8/0x190
> > > > [ 90.335018] tty_release_struct+0x24/0x8c
> > > > [ 90.339022] tty_release+0x3ec/0x4c0
> > > > [ 90.342593] __fput+0x70/0x234
> > > > [ 90.345652] ____fput+0x14/0x20
> > > > [ 90.348790] task_work_run+0x84/0x17c
> > > > [ 90.352455] do_exit+0x310/0x96c
> > > > [ 90.355688] do_group_exit+0x3c/0xa0
> > > > [ 90.359259] __arm64_sys_exit_group+0x1c/0x20
> > > > [ 90.363609] invoke_syscall+0x48/0x114
> > > > [ 90.367362] el0_svc_common.constprop.0+0xd4/0xfc
> > > > [ 90.372068] do_el0_svc+0x2c/0x94
> > > > [ 90.375379] el0_svc+0x28/0x80
> > > > [ 90.378438] el0t_64_sync_handler+0xa8/0x130
> > > > [ 90.382711] el0t_64_sync+0x1a0/0x1a4
> > > > [ 90.386376] Code: 17ffffda d503201f d503233f f9409802 (b9400041)
> > > > [ 90.392467] ---[ end trace 2f60524b4a43f1f6 ]---
> > > > [ 90.397073] note: btattach[503] exited with preempt_count 1
> > > > [ 90.402636] Fixing recursive fault but reboot is needed!
> > > >
> > > > Fixes: 6250cc30c4c4 ("tty: serial: fsl_lpuart: Use scatter/gather
> > > > DMA for Tx")
> > > > Signed-off-by: Thara Gopinath <[email protected]>
> > > > Signed-off-by: Sherry Sun <[email protected]>
> > > > ---
> > > > drivers/tty/serial/fsl_lpuart.c | 2 ++
> > > > 1 file changed, 2 insertions(+)
> > > >
> > > > diff --git a/drivers/tty/serial/fsl_lpuart.c
> > > > b/drivers/tty/serial/fsl_lpuart.c index f21915015d67..064bd1f33c21
> > > > 100644
> > > > --- a/drivers/tty/serial/fsl_lpuart.c
> > > > +++ b/drivers/tty/serial/fsl_lpuart.c
> > > > @@ -1771,6 +1771,7 @@ static void lpuart_dma_shutdown(struct
> > > lpuart_port *sport)
> > > > if (sport->lpuart_dma_rx_use) {
> > > > del_timer_sync(&sport->lpuart_timer);
> > > > lpuart_dma_rx_free(&sport->port);
> > > > + sport->lpuart_dma_rx_use = false;
> > > > }
> > > >
> > > > if (sport->lpuart_dma_tx_use) {
> > > > @@ -1779,6 +1780,7 @@ static void lpuart_dma_shutdown(struct
> > > lpuart_port *sport)
> > > > sport->dma_tx_in_progress = false;
> > > > dmaengine_terminate_all(sport->dma_tx_chan);
> > > > }
> > > > + sport->lpuart_dma_tx_use = false;
> > > > }
> > > >
> > > > if (sport->dma_tx_chan)
> > >
> > > Isn't it still racy because lpuart_dma_shutdown() is called outside
> > > of port's lock?
> >
> > Hi Ilpo, do you think add the following changes should work for this?
> >
> > diff --git a/drivers/tty/serial/fsl_lpuart.c
> > b/drivers/tty/serial/fsl_lpuart.c index 064bd1f33c21..b3c53935fbc8
> > 100644
> > --- a/drivers/tty/serial/fsl_lpuart.c
> > +++ b/drivers/tty/serial/fsl_lpuart.c
> > @@ -1768,10 +1768,14 @@ static int lpuart32_startup(struct uart_port
> > *port)
> >
> > static void lpuart_dma_shutdown(struct lpuart_port *sport) {
> > + unsigned long flags;
> > +
> > if (sport->lpuart_dma_rx_use) {
> > del_timer_sync(&sport->lpuart_timer);
> > lpuart_dma_rx_free(&sport->port);
> > + spin_lock_irqsave(&sport->port.lock, flags);
> > sport->lpuart_dma_rx_use = false;
> > + spin_unlock_irqrestore(&sport->port.lock, flags);
> > }
> >
> > if (sport->lpuart_dma_tx_use) { @@ -1780,7 +1784,9 @@ static
> > void lpuart_dma_shutdown(struct lpuart_port *sport)
> > sport->dma_tx_in_progress = false;
> > dmaengine_terminate_all(sport->dma_tx_chan);
> > }
> > + spin_lock_irqsave(&sport->port.lock, flags);
> > sport->lpuart_dma_tx_use = false;
> > + spin_unlock_irqrestore(&sport->port.lock, flags);
> > }
>
> After reading a bit more, I think the original patch is likely fine since
> shutdown doesn't seem to be racing with flush_buffer.
>
Good, thanks for the updates.
Best Regards
Sherry