Commit 10e5e375 authored by Vijay Viswanath's avatar Vijay Viswanath Committed by Martin K. Petersen
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_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: default avatarVijay Viswanath <vviswana@codeaurora.org>
Signed-off-by: default avatarCan Guo <cang@codeaurora.org>
Signed-off-by: default avatarAsutosh Das <asutoshd@codeaurora.org>
Reviewed-by: default avatarSubhash Jadavani <subhashj@codeaurora.org>
Signed-off-by: default avatarMartin K. Petersen <martin.petersen@oracle.com>
parent 7f6ba4f1

drivers/scsi/ufs/ufshcd.c

+10 −1
Original line number Diff line number Diff line
@@ -1532,7 +1532,8 @@ 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.clk_gating_workq,

			   &hba->clk_gating.ungate_work);

		/*

		 * fall through to check if we should wait for this

		 * work to be done or not.
@@ -1718,6 +1719,8 @@ out: 


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;
@@ -1725,6 +1728,11 @@ 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;
@@ -1752,6 +1760,7 @@ 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 */

drivers/scsi/ufs/ufshcd.h

+1 −0
Original line number Diff line number Diff line
@@ -362,6 +362,7 @@ 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 {

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