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SubjectRe: [PATCH 9/9] scsi: ufs: Add clock ungating to a separate workqueue
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On 2/24/2018 5:27 AM, Miguel Ojeda wrote:
> On Wed, Feb 21, 2018 at 5:56 AM, Asutosh Das <asutoshd@codeaurora.org> wrote:
>> From: Vijay Viswanath <vviswana@codeaurora.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__RECLAIM flag enabled.Such a workqueue will have
>
> WQ_MEM_RECLAIM here. Also space after dot.
>
>> a rescue thread which will be called when the above deadlock
>> condition is possible.
>>
>> Signed-off-by: Vijay Viswanath <vviswana@codeaurora.org>
>> Signed-off-by: Can Guo <cang@codeaurora.org>
>> Signed-off-by: Asutosh Das <asutoshd@codeaurora.org>
>> ---
>> drivers/scsi/ufs/ufshcd.c | 10 +++++++++-
>> drivers/scsi/ufs/ufshcd.h | 1 +
>> 2 files changed, 10 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
>> index 6541e1d..bb3382a 100644
>> --- a/drivers/scsi/ufs/ufshcd.c
>> +++ b/drivers/scsi/ufs/ufshcd.c
>> @@ -1503,7 +1503,8 @@ 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.
>> @@ -1689,6 +1690,8 @@ 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;
>>
>> @@ -1696,6 +1699,10 @@ 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 = create_singlethread_workqueue(wq_name);
>
> Shouldn't this be alloc_ordered_workqueue() with WQ_MEM_RECLAIM then?
> (create_singlethread_workqueue() and friends are deprecated).
>
> Cheers,
> Miguel
>
>> +
>> hba->clk_gating.is_enabled = true;
>>
>> hba->clk_gating.delay_attr.show = ufshcd_clkgate_delay_show;
>> @@ -1723,6 +1730,7 @@ 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 4385741..570c33e 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 {
>> --
>> Qualcomm India Private Limited, on behalf of Qualcomm Innovation Center, Inc.
>> Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux Foundation Collaborative Project.
>>

Hi Miguel
Thanks for the review.

I'll check this and put up the changes in v2.


-asd

--
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a
Linux Foundation Collaborative Project

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