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Commit f8f1e10c authored by Vijay Viswanath's avatar Vijay Viswanath
Browse files

scsi: ufs: Add clock ungating to a separate workqueue 



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
a rescue thread which will be called when the above deadlock
condition is possible.

Change-Id: I6b50e32a12c0279d12e82b278af9b2c2da82ff54
Signed-off-by: default avatarVijay Viswanath <vviswana@codeaurora.org>
parent e1420870

drivers/scsi/ufs/ufshcd.c

+8 −1
Original line number Diff line number Diff line
@@ -1273,7 +1273,8 @@ start: 
		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.ungating_workq,

				&hba->clk_gating.ungate_work);

		/*

		 * fall through to check if we should wait for this

		 * work to be done or not.
@@ -1522,6 +1523,7 @@ out: 
static void ufshcd_init_clk_gating(struct ufs_hba *hba)

{

	struct ufs_clk_gating *gating = &hba->clk_gating;

	char wq_name[sizeof("ufs_clk_ungating_00")];



	hba->clk_gating.state = CLKS_ON;
@@ -1531,6 +1533,10 @@ static void ufshcd_init_clk_gating(struct ufs_hba *hba) 
	INIT_DELAYED_WORK(&gating->gate_work, ufshcd_gate_work);

	INIT_WORK(&gating->ungate_work, ufshcd_ungate_work);



	snprintf(wq_name, ARRAY_SIZE(wq_name), "ufs_clk_ungating_%d",

			hba->host->host_no);

	hba->clk_gating.ungating_workq = create_singlethread_workqueue(wq_name);



	gating->is_enabled = true;



	/*
@@ -1607,6 +1613,7 @@ 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.ungating_workq);

}



/**

drivers/scsi/ufs/ufshcd.h

+1 −0
Original line number Diff line number Diff line
@@ -421,6 +421,7 @@ struct ufs_clk_gating { 
	struct device_attribute enable_attr;

	bool is_enabled;

	int active_reqs;

	struct workqueue_struct *ungating_workq;

};



/* Hibern8 state  */