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Message-ID: <9b3fe3b9f1bd2f7c36dcd840acf7848d@codeaurora.org>
Date: Wed, 16 May 2018 14:14:43 -0700
From: Subhash Jadavani <subhashj@...eaurora.org>
To: Asutosh Das <asutoshd@...eaurora.org>
Cc: cang@...eaurora.org, vivek.gautam@...eaurora.org,
rnayak@...eaurora.org, vinholikatti@...il.com,
jejb@...ux.vnet.ibm.com, martin.petersen@...cle.com,
linux-mmc@...r.kernel.org, linux-scsi@...r.kernel.org,
Vijay Viswanath <vviswana@...eaurora.org>,
linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-scsi-owner@...r.kernel.org
Subject: Re: [PATCH v2 10/10] scsi: ufs: Add clock ungating to a separate
workqueue
On 2018-05-03 04:07, Asutosh Das wrote:
> From: Vijay Viswanath <vviswana@...eaurora.org>
>
> UFS driver can receive a request during memory reclaim by kswapd.
> So when ufs driver puts the ungate work in queue, and if there are no
> idle workers, kthreadd is invoked to create a new kworker. Since
> kswapd task holds a mutex which kthreadd also needs, this can cause
> a deadlock situation. So ungate work must be done in a separate
> work queue with WQ_MEM_RECLAIM flag enabled.
> Such a workqueue will have a rescue thread which will be called
> when the above deadlock condition is possible.
>
> Signed-off-by: Vijay Viswanath <vviswana@...eaurora.org>
> Signed-off-by: Can Guo <cang@...eaurora.org>
> Signed-off-by: Asutosh Das <asutoshd@...eaurora.org>
> ---
> drivers/scsi/ufs/ufshcd.c | 11 ++++++++++-
> drivers/scsi/ufs/ufshcd.h | 1 +
> 2 files changed, 11 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
> index 557d538..3be61b7 100644
> --- a/drivers/scsi/ufs/ufshcd.c
> +++ b/drivers/scsi/ufs/ufshcd.c
> @@ -1483,7 +1483,8 @@ int ufshcd_hold(struct ufs_hba *hba, bool async)
> hba->clk_gating.state = REQ_CLKS_ON;
> trace_ufshcd_clk_gating(dev_name(hba->dev),
> hba->clk_gating.state);
> - schedule_work(&hba->clk_gating.ungate_work);
> + queue_work(hba->clk_gating.clk_gating_workq,
> + &hba->clk_gating.ungate_work);
> /*
> * fall through to check if we should wait for this
> * work to be done or not.
> @@ -1669,6 +1670,8 @@ static ssize_t
> ufshcd_clkgate_enable_store(struct device *dev,
>
> static void ufshcd_init_clk_gating(struct ufs_hba *hba)
> {
> + char wq_name[sizeof("ufs_clk_gating_00")];
> +
> if (!ufshcd_is_clkgating_allowed(hba))
> return;
>
> @@ -1676,6 +1679,11 @@ static void ufshcd_init_clk_gating(struct
> ufs_hba *hba)
> INIT_DELAYED_WORK(&hba->clk_gating.gate_work, ufshcd_gate_work);
> INIT_WORK(&hba->clk_gating.ungate_work, ufshcd_ungate_work);
>
> + snprintf(wq_name, ARRAY_SIZE(wq_name), "ufs_clk_gating_%d",
> + hba->host->host_no);
> + hba->clk_gating.clk_gating_workq = alloc_ordered_workqueue(wq_name,
> + WQ_MEM_RECLAIM);
> +
> hba->clk_gating.is_enabled = true;
>
> hba->clk_gating.delay_attr.show = ufshcd_clkgate_delay_show;
> @@ -1703,6 +1711,7 @@ static void ufshcd_exit_clk_gating(struct ufs_hba
> *hba)
> device_remove_file(hba->dev, &hba->clk_gating.enable_attr);
> cancel_work_sync(&hba->clk_gating.ungate_work);
> cancel_delayed_work_sync(&hba->clk_gating.gate_work);
> + destroy_workqueue(hba->clk_gating.clk_gating_workq);
> }
>
> /* Must be called with host lock acquired */
> diff --git a/drivers/scsi/ufs/ufshcd.h b/drivers/scsi/ufs/ufshcd.h
> index 76c31d5..2e6bdc0 100644
> --- a/drivers/scsi/ufs/ufshcd.h
> +++ b/drivers/scsi/ufs/ufshcd.h
> @@ -361,6 +361,7 @@ struct ufs_clk_gating {
> struct device_attribute enable_attr;
> bool is_enabled;
> int active_reqs;
> + struct workqueue_struct *clk_gating_workq;
> };
>
> struct ufs_saved_pwr_info {
Looks good to me.
Reviewed-by: Subhash Jadavani <subhashj@...eaurora.org>
--
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