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

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Date:   Wed, 17 Oct 2018 13:26:32 -0700
From:   Stephen Boyd <sboyd@...nel.org>
To:     "James E.J. Bottomley" <jejb@...ux.vnet.ibm.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        Evan Green <evgreen@...omium.org>,
        Vinayak Holikatti <vinholikatti@...il.com>,
        linux-kernel@...r.kernel.org, linux-scsi@...r.kernel.org,
        sayalil@...eaurora.org
Cc:     Evan Green <evgreen@...omium.org>
Subject: Re: [PATCH] scsi: ufs: Schedule clk gating work on correct queue

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@...omium.org>
> 
> ---

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