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Date: Wed, 21 Feb 2018 10:26:40 +0530 From: Asutosh Das <asutoshd@...eaurora.org> To: subhashj@...eaurora.org, cang@...eaurora.org, vivek.gautam@...eaurora.org, rnayak@...eaurora.org, vinholikatti@...il.com, jejb@...ux.vnet.ibm.com, martin.petersen@...cle.com Cc: linux-scsi@...r.kernel.org, Vijay Viswanath <vviswana@...eaurora.org>, Asutosh Das <asutoshd@...eaurora.org>, linux-kernel@...r.kernel.org (open list) Subject: [PATCH 9/9] scsi: ufs: Add clock ungating to a separate workqueue From: Vijay Viswanath <vviswana@...eaurora.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__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@...eaurora.org> Signed-off-by: Can Guo <cang@...eaurora.org> Signed-off-by: Asutosh Das <asutoshd@...eaurora.org> --- drivers/scsi/ufs/ufshcd.c | 10 +++++++++- drivers/scsi/ufs/ufshcd.h | 1 + 2 files changed, 10 insertions(+), 1 deletion(-) diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c index 6541e1d..bb3382a 100644 --- a/drivers/scsi/ufs/ufshcd.c +++ b/drivers/scsi/ufs/ufshcd.c @@ -1503,7 +1503,8 @@ 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. @@ -1689,6 +1690,8 @@ 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; @@ -1696,6 +1699,10 @@ 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 = create_singlethread_workqueue(wq_name); + hba->clk_gating.is_enabled = true; hba->clk_gating.delay_attr.show = ufshcd_clkgate_delay_show; @@ -1723,6 +1730,7 @@ 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 4385741..570c33e 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.
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