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From: Asutosh Das <asutoshd@codeaurora.org>
To: subhashj@codeaurora.org, cang@codeaurora.org,
	vivek.gautam@codeaurora.org, rnayak@codeaurora.org,
	vinholikatti@gmail.com, jejb@linux.vnet.ibm.com,
	martin.petersen@oracle.com, asutoshd@codeaurora.org,
	linux-mmc@vger.kernel.org
Cc: linux-scsi@vger.kernel.org,
	Vijay Viswanath <vviswana@codeaurora.org>,
	linux-arm-msm@vger.kernel.org,
	linux-kernel@vger.kernel.org (open list)
Subject: [PATCH v2 10/10] scsi: ufs: Add clock ungating to a separate workqueue
Date: Thu,  3 May 2018 16:37:22 +0530	[thread overview]
Message-ID: <0bfae28dbfb4cf86e80435639b92c7f4023041dc.1525343531.git.asutoshd@codeaurora.org> (raw)
In-Reply-To: <cover.1525341340.git.asutoshd@codeaurora.org>
In-Reply-To: <cover.1525343531.git.asutoshd@codeaurora.org>

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_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@codeaurora.org>
Signed-off-by: Can Guo <cang@codeaurora.org>
Signed-off-by: Asutosh Das <asutoshd@codeaurora.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 {
-- 
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.

  parent reply	other threads:[~2018-05-03 11:15 UTC|newest]

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <cover.1525341340.git.asutoshd@codeaurora.org>
     [not found] ` <cover.1525343531.git.asutoshd@codeaurora.org>
2018-05-03 11:07   ` [PATCH v2 01/10] scsi: ufs: Allowing power mode change Asutosh Das
2018-05-16 21:09     ` Subhash Jadavani
2018-05-03 11:07   ` [PATCH v2 02/10] scsi: ufs-qcom: Enable UFSHCD_QUIRK_BROKEN_PWR_MODE_CHANGE quirk Asutosh Das
2018-05-16 21:10     ` Subhash Jadavani
2018-05-03 11:07   ` [PATCH v2 03/10] scsi: ufs: Add LCC quirk for host and device Asutosh Das
2018-05-16 21:11     ` Subhash Jadavani
2018-05-03 11:07   ` [PATCH v2 04/10] scsi: ufs: fix exception event handling Asutosh Das
2018-05-16 21:12     ` Subhash Jadavani
2018-05-03 11:07   ` [PATCH v2 05/10] scsi: ufshcd: fix possible unclocked register access Asutosh Das
2018-05-16 21:12     ` Subhash Jadavani
2018-05-03 11:07   ` [PATCH v2 06/10] scsi: ufs: add reference counting for scsi block requests Asutosh Das
2018-05-16 21:13     ` Subhash Jadavani
2018-05-03 11:07   ` [PATCH v2 07/10] scsi: ufs-qcom: remove broken hci version quirk Asutosh Das
2018-05-16 21:13     ` Subhash Jadavani
2018-05-03 11:07   ` [PATCH v2 08/10] scsi: ufs: make sure all interrupts are processed Asutosh Das
2018-05-16 21:14     ` Subhash Jadavani
2018-05-03 11:07   ` [PATCH v2 09/10] scsi: ufs: fix irq return code Asutosh Das
2018-06-28 22:26     ` Subhash Jadavani
2018-05-03 11:07   ` Asutosh Das [this message]
2018-05-16 21:14     ` [PATCH v2 10/10] scsi: ufs: Add clock ungating to a separate workqueue Subhash Jadavani

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