From db0785db9ae779a2dc25966a12e951ed3d55e195 Mon Sep 17 00:00:00 2001 From: Vijay Viswanath Date: Tue, 15 Nov 2016 11:02:03 +0530 Subject: [PATCH] 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: I91c5bff812be403addc98fbb8c620e67cf28f5d9 Signed-off-by: Vijay Viswanath --- drivers/scsi/ufs/ufshcd.c | 9 ++++++++- drivers/scsi/ufs/ufshcd.h | 1 + 2 files changed, 9 insertions(+), 1 deletion(-) diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c index 6e88e4b11273..2138e81bb9e9 100644 --- a/drivers/scsi/ufs/ufshcd.c +++ b/drivers/scsi/ufs/ufshcd.c @@ -1344,7 +1344,8 @@ 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. @@ -1617,6 +1618,7 @@ static enum hrtimer_restart ufshcd_clkgate_hrtimer_handler( 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; @@ -1645,6 +1647,10 @@ static void ufshcd_init_clk_gating(struct ufs_hba *hba) hrtimer_init(&gating->gate_hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); gating->gate_hrtimer.function = ufshcd_clkgate_hrtimer_handler; + 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; gating->delay_ms_pwr_save = UFSHCD_CLK_GATING_DELAY_MS_PWR_SAVE; @@ -1707,6 +1713,7 @@ static void ufshcd_exit_clk_gating(struct ufs_hba *hba) device_remove_file(hba->dev, &hba->clk_gating.enable_attr); ufshcd_cancel_gate_work(hba); cancel_work_sync(&hba->clk_gating.ungate_work); + destroy_workqueue(hba->clk_gating.ungating_workq); } static void ufshcd_set_auto_hibern8_timer(struct ufs_hba *hba, u32 delay) diff --git a/drivers/scsi/ufs/ufshcd.h b/drivers/scsi/ufs/ufshcd.h index b20afd85beab..c34a998aac17 100644 --- a/drivers/scsi/ufs/ufshcd.h +++ b/drivers/scsi/ufs/ufshcd.h @@ -431,6 +431,7 @@ struct ufs_clk_gating { struct device_attribute enable_attr; bool is_enabled; int active_reqs; + struct workqueue_struct *ungating_workq; }; /* Hibern8 state */