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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: Vijay Viswanath <vviswana@codeaurora.org>
Signed-off-by: Can Guo <cang@codeaurora.org>
Signed-off-by: Asutosh Das <asutoshd@codeaurora.org>
Reviewed-by: Subhash Jadavani <subhashj@codeaurora.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
This commit is contained in:
Vijay Viswanath 2018-05-03 16:37:22 +05:30 committed by Martin K. Petersen
parent 7f6ba4f12e
commit 10e5e37581
2 changed files with 11 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

11
drivers/scsi/ufs/ufshcd.c
View File

@ -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 */

1
drivers/scsi/ufs/ufshcd.h
View File

@ -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 {