On 7/26/22 11:05 PM, Greg KH wrote:
On Tue, Jul 26, 2022 at 05:14:33PM +0800, peter.wang@mediatek.com wrote:
From: Peter Wang peter.wang@mediatek.com
There have a lockdep warning like below in current flow. kworker/u16:0: Possible unsafe locking scenario:
kworker/u16:0: CPU0 CPU1 kworker/u16:0: ---- ---- kworker/u16:0: lock(&hba->clk_scaling_lock); kworker/u16:0: lock(&hba->dev_cmd.lock); kworker/u16:0: lock(&hba->clk_scaling_lock); kworker/u16:0: lock(&hba->dev_cmd.lock); kworker/u16:0:
Before this patch clk_scaling_lock was held in reader mode during the ufshcd_wb_toggle() call. With this patch applied clk_scaling_lock is not held while ufshcd_wb_toggle() is called.
This is safe because ufshcd_wb_toggle will held clk_scaling_lock in reader mode "again" in flow ufshcd_wb_toggle -> __ufshcd_wb_toggle -> ufshcd_query_flag_retry -> ufshcd_query_flag -> ufshcd_exec_dev_cmd -> down_read(&hba->clk_scaling_lock); The protect should enough and make sure clock is not change while send command.
ufshcd_wb_toggle can protected by hba->clk_scaling.is_allowed to make sure ufshcd_devfreq_scale function not run concurrently.
Fixes: 0e9d4ca43ba8 ("scsi: ufs: Protect some contexts from unexpected clock scaling") Signed-off-by: Peter Wang peter.wang@mediatek.com
drivers/ufs/core/ufshcd.c | 27 ++++++++++++++++----------- 1 file changed, 16 insertions(+), 11 deletions(-)
diff --git a/drivers/ufs/core/ufshcd.c b/drivers/ufs/core/ufshcd.c index c7b337480e3e..aa57126fdb49 100644 --- a/drivers/ufs/core/ufshcd.c +++ b/drivers/ufs/core/ufshcd.c @@ -272,6 +272,7 @@ static void ufshcd_wb_toggle_flush_during_h8(struct ufs_hba *hba, bool set); static inline void ufshcd_wb_toggle_flush(struct ufs_hba *hba, bool enable); static void ufshcd_hba_vreg_set_lpm(struct ufs_hba *hba); static void ufshcd_hba_vreg_set_hpm(struct ufs_hba *hba); +static void ufshcd_clk_scaling_allow(struct ufs_hba *hba, bool allow); static inline void ufshcd_enable_irq(struct ufs_hba *hba) { @@ -1249,12 +1250,10 @@ static int ufshcd_clock_scaling_prepare(struct ufs_hba *hba) return ret; } -static void ufshcd_clock_scaling_unprepare(struct ufs_hba *hba, bool writelock) +static void ufshcd_clock_scaling_unprepare(struct ufs_hba *hba) {
- if (writelock)
up_write(&hba->clk_scaling_lock);- else
up_read(&hba->clk_scaling_lock);
- up_write(&hba->clk_scaling_lock);
- ufshcd_scsi_unblock_requests(hba); ufshcd_release(hba); }
@@ -1271,7 +1270,7 @@ static void ufshcd_clock_scaling_unprepare(struct ufs_hba *hba, bool writelock) static int ufshcd_devfreq_scale(struct ufs_hba *hba, bool scale_up) { int ret = 0;
- bool is_writelock = true;
- bool wb_toggle = false;
ret = ufshcd_clock_scaling_prepare(hba); if (ret) @@ -1300,13 +1299,19 @@ static int ufshcd_devfreq_scale(struct ufs_hba *hba, bool scale_up) } }
- /* Enable Write Booster if we have scaled up else disable it */
- downgrade_write(&hba->clk_scaling_lock);
- is_writelock = false;
- ufshcd_wb_toggle(hba, scale_up);
- /* Disable clk_scaling until ufshcd_wb_toggle finish */
- hba->clk_scaling.is_allowed = false;
- wb_toggle = true;
out_unprepare:
- ufshcd_clock_scaling_unprepare(hba, is_writelock);
- ufshcd_clock_scaling_unprepare(hba);
- /* Enable Write Booster if we have scaled up else disable it */
- if (wb_toggle) {
ufshcd_wb_toggle(hba, scale_up);ufshcd_clk_scaling_allow(hba, true);- }
- return ret; }
2.18.0
<formletter>
This is not the correct way to submit patches for inclusion in the stable kernel tree. Please read: https://urldefense.com/v3/__https://www.kernel.org/doc/html/latest/process/s... for how to do this properly.
Hi Greg,
Thank you for remind.
Will use correct way next version
Thanks
Peter
</formletter>