* [PATCH] scsi: ufs: initialize devfreq synchronously
@ 2023-02-09 21:14 Adrien Thierry
2023-02-10 17:51 ` Bean Huo
2023-02-15 18:50 ` Bart Van Assche
0 siblings, 2 replies; 4+ messages in thread
From: Adrien Thierry @ 2023-02-09 21:14 UTC (permalink / raw)
To: Alim Akhtar, Avri Altman, Bart Van Assche, James E.J. Bottomley,
Martin K. Petersen
Cc: Adrien Thierry, linux-scsi
During ufs initialization, devfreq initialization is asynchronous:
ufshcd_async_scan() calls ufshcd_add_lus(), which in turn initializes
devfreq for ufs. The simple ondemand governor is then loaded. If it is
build as a module, request_module() is called and throws a warning:
WARNING: CPU: 7 PID: 167 at kernel/kmod.c:136 __request_module+0x1e0/0x460
Modules linked in: crct10dif_ce llcc_qcom phy_qcom_qmp_usb ufs_qcom phy_qcom_snps_femto_v2 ufshcd_pltfrm phy_qcom_qmp_combo ufshcd_core phy_qcom_qmp_ufs qcom_wdt socinfo fuse ipv6
CPU: 7 PID: 167 Comm: kworker/u16:3 Not tainted 6.2.0-rc6-00009-g58706f7fb045 #1
Hardware name: Qualcomm SA8540P Ride (DT)
Workqueue: events_unbound async_run_entry_fn
pstate: 00400005 (nzcv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
pc : __request_module+0x1e0/0x460
lr : __request_module+0x1d8/0x460
sp : ffff800009323b90
x29: ffff800009323b90 x28: 0000000000000000 x27: 0000000000000000
x26: ffff800009323d50 x25: ffff7b9045f57810 x24: ffff7b9045f57830
x23: ffffdc5a83e426e8 x22: ffffdc5ae80a9818 x21: 0000000000000001
x20: ffffdc5ae7502f98 x19: ffff7b9045f57800 x18: ffffffffffffffff
x17: 312f716572667665 x16: 642f7366752e3030 x15: 0000000000000000
x14: 000000000000021c x13: 0000000000005400 x12: ffff7b9042ed7614
x11: ffff7b9042ed7600 x10: 00000000636c0890 x9 : 0000000000000038
x8 : ffff7b9045f2c880 x7 : ffff7b9045f57c68 x6 : 0000000000000080
x5 : 0000000000000000 x4 : 8000000000000000 x3 : 0000000000000000
x2 : 0000000000000000 x1 : ffffdc5ae5d382f0 x0 : 0000000000000001
Call trace:
__request_module+0x1e0/0x460
try_then_request_governor+0x7c/0x100
devfreq_add_device+0x4b0/0x5fc
ufshcd_async_scan+0x1d4/0x310 [ufshcd_core]
async_run_entry_fn+0x34/0xe0
process_one_work+0x1d0/0x320
worker_thread+0x14c/0x444
kthread+0x10c/0x110
ret_from_fork+0x10/0x20
This occurs because synchronous module loading from async is not
allowed. According to __request_module():
/*
* We don't allow synchronous module loading from async. Module
* init may invoke async_synchronize_full() which will end up
* waiting for this task which already is waiting for the module
* loading to complete, leading to a deadlock.
*/
I experienced such a deadlock on the Qualcomm QDrive3/sa8540p-ride. With
DEVFREQ_GOV_SIMPLE_ONDEMAND=m, the boot hangs after the warning.
This patch fixes both the warning and the deadlock, by moving devfreq
initialization out of the async routine.
I tested this on the sa8540p-ride by using fio to put the UFS under
load, and printing the trace generated by
/sys/kernel/tracing/events/ufs/ufshcd_clk_scaling events. The trace
looks similar with and without the change.
Signed-off-by: Adrien Thierry <athierry@redhat.com>
---
drivers/ufs/core/ufshcd.c | 40 ++++++++++++++++++++++-----------------
include/ufs/ufshcd.h | 1 +
2 files changed, 24 insertions(+), 17 deletions(-)
diff --git a/drivers/ufs/core/ufshcd.c b/drivers/ufs/core/ufshcd.c
index 3a1c4d31e010..17189934d1ae 100644
--- a/drivers/ufs/core/ufshcd.c
+++ b/drivers/ufs/core/ufshcd.c
@@ -1357,6 +1357,9 @@ static int ufshcd_devfreq_target(struct device *dev,
struct ufs_clk_info *clki;
unsigned long irq_flags;
+ if (!hba->is_initialized)
+ return 0;
+
if (!ufshcd_is_clkscaling_supported(hba))
return -EINVAL;
@@ -8136,22 +8139,6 @@ static int ufshcd_add_lus(struct ufs_hba *hba)
if (ret)
goto out;
- /* Initialize devfreq after UFS device is detected */
- if (ufshcd_is_clkscaling_supported(hba)) {
- memcpy(&hba->clk_scaling.saved_pwr_info.info,
- &hba->pwr_info,
- sizeof(struct ufs_pa_layer_attr));
- hba->clk_scaling.saved_pwr_info.is_valid = true;
- hba->clk_scaling.is_allowed = true;
-
- ret = ufshcd_devfreq_init(hba);
- if (ret)
- goto out;
-
- hba->clk_scaling.is_enabled = true;
- ufshcd_init_clk_scaling_sysfs(hba);
- }
-
ufs_bsg_probe(hba);
ufshpb_init(hba);
scsi_scan_host(hba->host);
@@ -8290,7 +8277,8 @@ static void ufshcd_async_scan(void *data, async_cookie_t cookie)
if (ret) {
pm_runtime_put_sync(hba->dev);
ufshcd_hba_exit(hba);
- }
+ } else
+ hba->is_initialized = true;
}
static enum scsi_timeout_action ufshcd_eh_timed_out(struct scsi_cmnd *scmd)
@@ -9896,12 +9884,30 @@ int ufshcd_init(struct ufs_hba *hba, void __iomem *mmio_base, unsigned int irq)
*/
ufshcd_set_ufs_dev_active(hba);
+ /* Initialize devfreq */
+ if (ufshcd_is_clkscaling_supported(hba)) {
+ memcpy(&hba->clk_scaling.saved_pwr_info.info,
+ &hba->pwr_info,
+ sizeof(struct ufs_pa_layer_attr));
+ hba->clk_scaling.saved_pwr_info.is_valid = true;
+ hba->clk_scaling.is_allowed = true;
+
+ err = ufshcd_devfreq_init(hba);
+ if (err)
+ goto out_power_off;
+
+ hba->clk_scaling.is_enabled = true;
+ ufshcd_init_clk_scaling_sysfs(hba);
+ }
+
async_schedule(ufshcd_async_scan, hba);
ufs_sysfs_add_nodes(hba->dev);
device_enable_async_suspend(dev);
return 0;
+out_power_off:
+ pm_runtime_put_sync(dev);
free_tmf_queue:
blk_mq_destroy_queue(hba->tmf_queue);
blk_put_queue(hba->tmf_queue);
diff --git a/include/ufs/ufshcd.h b/include/ufs/ufshcd.h
index 727084cd79be..58a78dcd3472 100644
--- a/include/ufs/ufshcd.h
+++ b/include/ufs/ufshcd.h
@@ -896,6 +896,7 @@ struct ufs_hba {
struct completion *uic_async_done;
enum ufshcd_state ufshcd_state;
+ bool is_initialized;
u32 eh_flags;
u32 intr_mask;
u16 ee_ctrl_mask;
--
2.39.1
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH] scsi: ufs: initialize devfreq synchronously
2023-02-09 21:14 [PATCH] scsi: ufs: initialize devfreq synchronously Adrien Thierry
@ 2023-02-10 17:51 ` Bean Huo
2023-02-10 20:23 ` Adrien Thierry
2023-02-15 18:50 ` Bart Van Assche
1 sibling, 1 reply; 4+ messages in thread
From: Bean Huo @ 2023-02-10 17:51 UTC (permalink / raw)
To: Adrien Thierry, Alim Akhtar, Avri Altman, Bart Van Assche,
James E.J. Bottomley, Martin K. Petersen
Cc: linux-scsi
Adrien,
On 09.02.23 10:14 PM, Adrien Thierry wrote:
>
> - /* Initialize devfreq after UFS device is detected */
> - if (ufshcd_is_clkscaling_supported(hba)) {
> - memcpy(&hba->clk_scaling.saved_pwr_info.info,
> - &hba->pwr_info,
> - sizeof(struct ufs_pa_layer_attr));
> - hba->clk_scaling.saved_pwr_info.is_valid = true;
> - hba->clk_scaling.is_allowed = true;
> -
> - ret = ufshcd_devfreq_init(hba);
> - if (ret)
> - goto out;
> -
> - hba->clk_scaling.is_enabled = true;
> - ufshcd_init_clk_scaling_sysfs(hba);
> - }
> -
> ufs_bsg_probe(hba);
> ufshpb_init(hba);
> scsi_scan_host(hba->host);
> @@ -8290,7 +8277,8 @@ static void ufshcd_async_scan(void *data, async_cookie_t cookie)
> if (ret) {
> pm_runtime_put_sync(hba->dev);
> ufshcd_hba_exit(hba);
> - }
> + } else
> + hba->is_initialized = true;
after moving devfreq initialization out of the async routine, still has deadlock issue?
> }
>
> static enum scsi_timeout_action ufshcd_eh_timed_out(struct scsi_cmnd *scmd)
> @@ -9896,12 +9884,30 @@ int ufshcd_init(struct ufs_hba *hba, void __iomem *mmio_base, unsigned int irq)
> */
> ufshcd_set_ufs_dev_active(hba);
>
> + /* Initialize devfreq */
> + if (ufshcd_is_clkscaling_supported(hba)) {
> + memcpy(&hba->clk_scaling.saved_pwr_info.info,
> + &hba->pwr_info,
> + sizeof(struct ufs_pa_layer_attr));
> + hba->clk_scaling.saved_pwr_info.is_valid = true;
> + hba->clk_scaling.is_allowed = true;
> +
> + err = ufshcd_devfreq_init(hba);
> + if (err)
> + goto out_power_off;
> +
> + hba->clk_scaling.is_enabled = true;
> + ufshcd_init_clk_scaling_sysfs(hba);
> + }
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] scsi: ufs: initialize devfreq synchronously
2023-02-10 17:51 ` Bean Huo
@ 2023-02-10 20:23 ` Adrien Thierry
0 siblings, 0 replies; 4+ messages in thread
From: Adrien Thierry @ 2023-02-10 20:23 UTC (permalink / raw)
To: Bean Huo
Cc: Alim Akhtar, Avri Altman, Bart Van Assche, James E.J. Bottomley,
Martin K. Petersen, linux-scsi
Hi Bean,
> On 09.02.23 10:14 PM, Adrien Thierry wrote:
> > - /* Initialize devfreq after UFS device is detected */
> > - if (ufshcd_is_clkscaling_supported(hba)) {
> > - memcpy(&hba->clk_scaling.saved_pwr_info.info,
> > - &hba->pwr_info,
> > - sizeof(struct ufs_pa_layer_attr));
> > - hba->clk_scaling.saved_pwr_info.is_valid = true;
> > - hba->clk_scaling.is_allowed = true;
> > -
> > - ret = ufshcd_devfreq_init(hba);
> > - if (ret)
> > - goto out;
> > -
> > - hba->clk_scaling.is_enabled = true;
> > - ufshcd_init_clk_scaling_sysfs(hba);
> > - }
> > -
> > ufs_bsg_probe(hba);
> > ufshpb_init(hba);
> > scsi_scan_host(hba->host);
> > @@ -8290,7 +8277,8 @@ static void ufshcd_async_scan(void *data, async_cookie_t cookie)
> > if (ret) {
> > pm_runtime_put_sync(hba->dev);
> > ufshcd_hba_exit(hba);
> > - }
> > + } else
> > + hba->is_initialized = true;
>
> after moving devfreq initialization out of the async routine, still has deadlock issue?
>
No more deadlock after moving devfreq initialization out of the async
routine. The reason I added the hba->is_initialized variable is to prevent
devfreq_monitor to update the ufs frequency until the async routine had a
chance to run and the ufs is initialized. Otherwise I would sometimes get
"dvfs failed with (-16) error" on boot.
Best,
Adrien
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] scsi: ufs: initialize devfreq synchronously
2023-02-09 21:14 [PATCH] scsi: ufs: initialize devfreq synchronously Adrien Thierry
2023-02-10 17:51 ` Bean Huo
@ 2023-02-15 18:50 ` Bart Van Assche
1 sibling, 0 replies; 4+ messages in thread
From: Bart Van Assche @ 2023-02-15 18:50 UTC (permalink / raw)
To: Adrien Thierry, Alim Akhtar, Avri Altman, James E.J. Bottomley,
Martin K. Petersen
Cc: linux-scsi
On 2/9/23 13:14, Adrien Thierry wrote:
> During ufs initialization, devfreq initialization is asynchronous:
> ufshcd_async_scan() calls ufshcd_add_lus(), which in turn initializes
> devfreq for ufs. The simple ondemand governor is then loaded. If it is
> build as a module, request_module() is called and throws a warning:
>
> WARNING: CPU: 7 PID: 167 at kernel/kmod.c:136 __request_module+0x1e0/0x460
> Modules linked in: crct10dif_ce llcc_qcom phy_qcom_qmp_usb ufs_qcom phy_qcom_snps_femto_v2 ufshcd_pltfrm phy_qcom_qmp_combo ufshcd_core phy_qcom_qmp_ufs qcom_wdt socinfo fuse ipv6
> CPU: 7 PID: 167 Comm: kworker/u16:3 Not tainted 6.2.0-rc6-00009-g58706f7fb045 #1
> Hardware name: Qualcomm SA8540P Ride (DT)
> Workqueue: events_unbound async_run_entry_fn
> pstate: 00400005 (nzcv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
> pc : __request_module+0x1e0/0x460
> lr : __request_module+0x1d8/0x460
> sp : ffff800009323b90
> x29: ffff800009323b90 x28: 0000000000000000 x27: 0000000000000000
> x26: ffff800009323d50 x25: ffff7b9045f57810 x24: ffff7b9045f57830
> x23: ffffdc5a83e426e8 x22: ffffdc5ae80a9818 x21: 0000000000000001
> x20: ffffdc5ae7502f98 x19: ffff7b9045f57800 x18: ffffffffffffffff
> x17: 312f716572667665 x16: 642f7366752e3030 x15: 0000000000000000
> x14: 000000000000021c x13: 0000000000005400 x12: ffff7b9042ed7614
> x11: ffff7b9042ed7600 x10: 00000000636c0890 x9 : 0000000000000038
> x8 : ffff7b9045f2c880 x7 : ffff7b9045f57c68 x6 : 0000000000000080
> x5 : 0000000000000000 x4 : 8000000000000000 x3 : 0000000000000000
> x2 : 0000000000000000 x1 : ffffdc5ae5d382f0 x0 : 0000000000000001
> Call trace:
> __request_module+0x1e0/0x460
> try_then_request_governor+0x7c/0x100
> devfreq_add_device+0x4b0/0x5fc
> ufshcd_async_scan+0x1d4/0x310 [ufshcd_core]
> async_run_entry_fn+0x34/0xe0
> process_one_work+0x1d0/0x320
> worker_thread+0x14c/0x444
> kthread+0x10c/0x110
> ret_from_fork+0x10/0x20
>
> This occurs because synchronous module loading from async is not
> allowed. According to __request_module():
>
> /*
> * We don't allow synchronous module loading from async. Module
> * init may invoke async_synchronize_full() which will end up
> * waiting for this task which already is waiting for the module
> * loading to complete, leading to a deadlock.
> */
>
> I experienced such a deadlock on the Qualcomm QDrive3/sa8540p-ride. With
> DEVFREQ_GOV_SIMPLE_ONDEMAND=m, the boot hangs after the warning.
>
> This patch fixes both the warning and the deadlock, by moving devfreq
> initialization out of the async routine.
>
> I tested this on the sa8540p-ride by using fio to put the UFS under
> load, and printing the trace generated by
> /sys/kernel/tracing/events/ufs/ufshcd_clk_scaling events. The trace
> looks similar with and without the change.
>
> Signed-off-by: Adrien Thierry <athierry@redhat.com>
> ---
> drivers/ufs/core/ufshcd.c | 40 ++++++++++++++++++++++-----------------
> include/ufs/ufshcd.h | 1 +
> 2 files changed, 24 insertions(+), 17 deletions(-)
>
> diff --git a/drivers/ufs/core/ufshcd.c b/drivers/ufs/core/ufshcd.c
> index 3a1c4d31e010..17189934d1ae 100644
> --- a/drivers/ufs/core/ufshcd.c
> +++ b/drivers/ufs/core/ufshcd.c
> @@ -1357,6 +1357,9 @@ static int ufshcd_devfreq_target(struct device *dev,
> struct ufs_clk_info *clki;
> unsigned long irq_flags;
>
> + if (!hba->is_initialized)
> + return 0;
> +
> if (!ufshcd_is_clkscaling_supported(hba))
> return -EINVAL;
>
> @@ -8136,22 +8139,6 @@ static int ufshcd_add_lus(struct ufs_hba *hba)
> if (ret)
> goto out;
>
> - /* Initialize devfreq after UFS device is detected */
> - if (ufshcd_is_clkscaling_supported(hba)) {
> - memcpy(&hba->clk_scaling.saved_pwr_info.info,
> - &hba->pwr_info,
> - sizeof(struct ufs_pa_layer_attr));
> - hba->clk_scaling.saved_pwr_info.is_valid = true;
> - hba->clk_scaling.is_allowed = true;
> -
> - ret = ufshcd_devfreq_init(hba);
> - if (ret)
> - goto out;
> -
> - hba->clk_scaling.is_enabled = true;
> - ufshcd_init_clk_scaling_sysfs(hba);
> - }
> -
> ufs_bsg_probe(hba);
> ufshpb_init(hba);
> scsi_scan_host(hba->host);
> @@ -8290,7 +8277,8 @@ static void ufshcd_async_scan(void *data, async_cookie_t cookie)
> if (ret) {
> pm_runtime_put_sync(hba->dev);
> ufshcd_hba_exit(hba);
> - }
> + } else
> + hba->is_initialized = true;
> }
>
> static enum scsi_timeout_action ufshcd_eh_timed_out(struct scsi_cmnd *scmd)
> @@ -9896,12 +9884,30 @@ int ufshcd_init(struct ufs_hba *hba, void __iomem *mmio_base, unsigned int irq)
> */
> ufshcd_set_ufs_dev_active(hba);
>
> + /* Initialize devfreq */
> + if (ufshcd_is_clkscaling_supported(hba)) {
> + memcpy(&hba->clk_scaling.saved_pwr_info.info,
> + &hba->pwr_info,
> + sizeof(struct ufs_pa_layer_attr));
> + hba->clk_scaling.saved_pwr_info.is_valid = true;
> + hba->clk_scaling.is_allowed = true;
> +
> + err = ufshcd_devfreq_init(hba);
> + if (err)
> + goto out_power_off;
> +
> + hba->clk_scaling.is_enabled = true;
> + ufshcd_init_clk_scaling_sysfs(hba);
> + }
> +
> async_schedule(ufshcd_async_scan, hba);
> ufs_sysfs_add_nodes(hba->dev);
>
> device_enable_async_suspend(dev);
> return 0;
>
> +out_power_off:
> + pm_runtime_put_sync(dev);
> free_tmf_queue:
> blk_mq_destroy_queue(hba->tmf_queue);
> blk_put_queue(hba->tmf_queue);
> diff --git a/include/ufs/ufshcd.h b/include/ufs/ufshcd.h
> index 727084cd79be..58a78dcd3472 100644
> --- a/include/ufs/ufshcd.h
> +++ b/include/ufs/ufshcd.h
> @@ -896,6 +896,7 @@ struct ufs_hba {
> struct completion *uic_async_done;
>
> enum ufshcd_state ufshcd_state;
> + bool is_initialized;
> u32 eh_flags;
> u32 intr_mask;
> u16 ee_ctrl_mask;
Please make the following changes:
* Rename is_initialized into logical_unit_scan_finished or another name
that describes the purpose of this variable more clearly.
* Fix the races between the code that sets the is_initialized variable
and the code that reads it by using smp_load_acquire() and
smp_store_release() instead of an ordinary load and store.
* Document in ufshcd_devfreq_target() why the logical unit scan must
have completed.
Thanks,
Bart.
^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2023-02-15 18:51 UTC | newest]
Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed)
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2023-02-09 21:14 [PATCH] scsi: ufs: initialize devfreq synchronously Adrien Thierry
2023-02-10 17:51 ` Bean Huo
2023-02-10 20:23 ` Adrien Thierry
2023-02-15 18:50 ` Bart Van Assche
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