[PATCH] scsi: ufs: Schedule clk gating work on correct queue

[PATCH] scsi: ufs: Schedule clk gating work on correct queue

[Evan Green]

With commit 10e5e37581fc ("scsi: ufs: Add clock ungating to a separate
workqueue"), clock gating work was moved to a
separate work queue with WQ_MEM_RECLAIM set, since clock
gating could occur from a memory reclaim context. Unfortunately,
clk_gating.gate_work was left queued via schedule_delayed_work,
which is a system workqueue that does not have WQ_MEM_RECLAIM set.
Because ufshcd_ungate_work attempts to cancel gate_work, the
following warning appears:

[   14.174170] workqueue: WQ_MEM_RECLAIM ufs_clk_gating_0:ufshcd_ungate_work is flushing !WQ_MEM_RECLAIM events:ufshcd_gate_work
[   14.174179] WARNING: CPU: 4 PID: 173 at kernel/workqueue.c:2440 check_flush_dependency+0x110/0x118
[   14.205725] CPU: 4 PID: 173 Comm: kworker/u16:3 Not tainted 4.14.68 #1
[   14.212437] Hardware name: Google Cheza (rev1) (DT)
[   14.217459] Workqueue: ufs_clk_gating_0 ufshcd_ungate_work
[   14.223107] task: ffffffc0f6a40080 task.stack: ffffff800a490000
[   14.229195] PC is at check_flush_dependency+0x110/0x118
[   14.234569] LR is at check_flush_dependency+0x110/0x118
[   14.239944] pc : [<ffffff80080cad14>] lr : [<ffffff80080cad14>] pstate: 60c001c9
[   14.333050] Call trace:
[   14.427767] [<ffffff80080cad14>] check_flush_dependency+0x110/0x118
[   14.434219] [<ffffff80080cafec>] start_flush_work+0xac/0x1fc
[   14.440046] [<ffffff80080caeec>] flush_work+0x40/0x94
[   14.445246] [<ffffff80080cb288>] __cancel_work_timer+0x11c/0x1b8
[   14.451433] [<ffffff80080cb4b8>] cancel_delayed_work_sync+0x20/0x30
[   14.457886] [<ffffff80085b9294>] ufshcd_ungate_work+0x24/0xd0
[   14.463800] [<ffffff80080cfb04>] process_one_work+0x32c/0x690
[   14.469713] [<ffffff80080d0154>] worker_thread+0x218/0x338
[   14.475361] [<ffffff80080d527c>] kthread+0x120/0x130
[   14.480470] [<ffffff8008084814>] ret_from_fork+0x10/0x18

The simple solution is to put the gate_work on the same WQ_MEM_RECLAIM
work queue as the ungate_work.

Fixes: 10e5e37581fc ("scsi: ufs: Add clock ungating to a separate workqueue")
Signed-off-by: Evan Green <evgreen@chromium.org>

---
 drivers/scsi/ufs/ufshcd.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
index c55f38ec391c..54074dd483a7 100644
--- a/drivers/scsi/ufs/ufshcd.c
+++ b/drivers/scsi/ufs/ufshcd.c
@@ -1691,8 +1691,9 @@ static void __ufshcd_release(struct ufs_hba *hba)
 
 	hba->clk_gating.state = REQ_CLKS_OFF;
 	trace_ufshcd_clk_gating(dev_name(hba->dev), hba->clk_gating.state);
-	schedule_delayed_work(&hba->clk_gating.gate_work,
-			msecs_to_jiffies(hba->clk_gating.delay_ms));
+	queue_delayed_work(hba->clk_gating.clk_gating_workq,
+			   &hba->clk_gating.gate_work,
+			   msecs_to_jiffies(hba->clk_gating.delay_ms));
 }
 
 void ufshcd_release(struct ufs_hba *hba)
-- 
2.16.4

Re: [PATCH] scsi: ufs: Schedule clk gating work on correct queue

[Doug Anderson]

Hi,

On Fri, Oct 5, 2018 at 10:28 AM Evan Green <evgreen@chromium.org> wrote:
>
> With commit 10e5e37581fc ("scsi: ufs: Add clock ungating to a separate
> workqueue"), clock gating work was moved to a
> separate work queue with WQ_MEM_RECLAIM set, since clock
> gating could occur from a memory reclaim context. Unfortunately,
> clk_gating.gate_work was left queued via schedule_delayed_work,
> which is a system workqueue that does not have WQ_MEM_RECLAIM set.
> Because ufshcd_ungate_work attempts to cancel gate_work, the
> following warning appears:
>
> [   14.174170] workqueue: WQ_MEM_RECLAIM ufs_clk_gating_0:ufshcd_ungate_work is flushing !WQ_MEM_RECLAIM events:ufshcd_gate_work
> [   14.174179] WARNING: CPU: 4 PID: 173 at kernel/workqueue.c:2440 check_flush_dependency+0x110/0x118
> [   14.205725] CPU: 4 PID: 173 Comm: kworker/u16:3 Not tainted 4.14.68 #1
> [   14.212437] Hardware name: Google Cheza (rev1) (DT)
> [   14.217459] Workqueue: ufs_clk_gating_0 ufshcd_ungate_work
> [   14.223107] task: ffffffc0f6a40080 task.stack: ffffff800a490000
> [   14.229195] PC is at check_flush_dependency+0x110/0x118
> [   14.234569] LR is at check_flush_dependency+0x110/0x118
> [   14.239944] pc : [<ffffff80080cad14>] lr : [<ffffff80080cad14>] pstate: 60c001c9
> [   14.333050] Call trace:
> [   14.427767] [<ffffff80080cad14>] check_flush_dependency+0x110/0x118
> [   14.434219] [<ffffff80080cafec>] start_flush_work+0xac/0x1fc
> [   14.440046] [<ffffff80080caeec>] flush_work+0x40/0x94
> [   14.445246] [<ffffff80080cb288>] __cancel_work_timer+0x11c/0x1b8
> [   14.451433] [<ffffff80080cb4b8>] cancel_delayed_work_sync+0x20/0x30
> [   14.457886] [<ffffff80085b9294>] ufshcd_ungate_work+0x24/0xd0
> [   14.463800] [<ffffff80080cfb04>] process_one_work+0x32c/0x690
> [   14.469713] [<ffffff80080d0154>] worker_thread+0x218/0x338
> [   14.475361] [<ffffff80080d527c>] kthread+0x120/0x130
> [   14.480470] [<ffffff8008084814>] ret_from_fork+0x10/0x18
>
> The simple solution is to put the gate_work on the same WQ_MEM_RECLAIM
> work queue as the ungate_work.
>
> Fixes: 10e5e37581fc ("scsi: ufs: Add clock ungating to a separate workqueue")
> Signed-off-by: Evan Green <evgreen@chromium.org>
>
> ---
>  drivers/scsi/ufs/ufshcd.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)

Seems sane to me:

Reviewed-by: Douglas Anderson <dianders@chromium.org>

Re: [PATCH] scsi: ufs: Schedule clk gating work on correct queue

[Stephen Boyd]

Quoting Evan Green (2018-10-05 10:27:32)
> With commit 10e5e37581fc ("scsi: ufs: Add clock ungating to a separate
> workqueue"), clock gating work was moved to a
> separate work queue with WQ_MEM_RECLAIM set, since clock
> gating could occur from a memory reclaim context. Unfortunately,
> clk_gating.gate_work was left queued via schedule_delayed_work,
> which is a system workqueue that does not have WQ_MEM_RECLAIM set.
> Because ufshcd_ungate_work attempts to cancel gate_work, the
> following warning appears:
> 
> [   14.174170] workqueue: WQ_MEM_RECLAIM ufs_clk_gating_0:ufshcd_ungate_work is flushing !WQ_MEM_RECLAIM events:ufshcd_gate_work
> [   14.174179] WARNING: CPU: 4 PID: 173 at kernel/workqueue.c:2440 check_flush_dependency+0x110/0x118
> [   14.205725] CPU: 4 PID: 173 Comm: kworker/u16:3 Not tainted 4.14.68 #1
> [   14.212437] Hardware name: Google Cheza (rev1) (DT)
> [   14.217459] Workqueue: ufs_clk_gating_0 ufshcd_ungate_work
> [   14.223107] task: ffffffc0f6a40080 task.stack: ffffff800a490000
> [   14.229195] PC is at check_flush_dependency+0x110/0x118
> [   14.234569] LR is at check_flush_dependency+0x110/0x118
> [   14.239944] pc : [<ffffff80080cad14>] lr : [<ffffff80080cad14>] pstate: 60c001c9
> [   14.333050] Call trace:
> [   14.427767] [<ffffff80080cad14>] check_flush_dependency+0x110/0x118
> [   14.434219] [<ffffff80080cafec>] start_flush_work+0xac/0x1fc
> [   14.440046] [<ffffff80080caeec>] flush_work+0x40/0x94
> [   14.445246] [<ffffff80080cb288>] __cancel_work_timer+0x11c/0x1b8
> [   14.451433] [<ffffff80080cb4b8>] cancel_delayed_work_sync+0x20/0x30
> [   14.457886] [<ffffff80085b9294>] ufshcd_ungate_work+0x24/0xd0
> [   14.463800] [<ffffff80080cfb04>] process_one_work+0x32c/0x690
> [   14.469713] [<ffffff80080d0154>] worker_thread+0x218/0x338
> [   14.475361] [<ffffff80080d527c>] kthread+0x120/0x130
> [   14.480470] [<ffffff8008084814>] ret_from_fork+0x10/0x18
> 
> The simple solution is to put the gate_work on the same WQ_MEM_RECLAIM
> work queue as the ungate_work.
> 
> Fixes: 10e5e37581fc ("scsi: ufs: Add clock ungating to a separate workqueue")
> Signed-off-by: Evan Green <evgreen@chromium.org>
> 
> ---

Reviewed-by: Stephen Boyd <swboyd@chromium.org>

Re: [PATCH] scsi: ufs: Schedule clk gating work on correct queue

[Martin K. Petersen]

Evan,

> With commit 10e5e37581fc ("scsi: ufs: Add clock ungating to a separate
> workqueue"), clock gating work was moved to a separate work queue with
> WQ_MEM_RECLAIM set, since clock gating could occur from a memory
> reclaim context. Unfortunately, clk_gating.gate_work was left queued
> via schedule_delayed_work, which is a system workqueue that does not
> have WQ_MEM_RECLAIM set.

Applied to 4.20/scsi-queue, thanks!

-- 
Martin K. Petersen	Oracle Linux Engineering