| Message ID | 20220722095308.10112-1-peter.wang@mediatek.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v1] ufs: core: fix lockdep warning of clk_scaling_lock | expand |
On 7/22/22 02:53, peter.wang@mediatek.com wrote: > This patch only release write lock of clk_scaling_lock before > ufshcd_wb_toggle. The above is not clear to me. Please make the above more clear. Additionally, patches must be signed before these can be merged upstream. Where is your Signed-off-by? > - /* 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); > + 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); > + > return ret; > } The patch description should mention that this patch changes the ufshcd_wb_toggle() call: before this patch clk_scaling_lock was held in reader mode during the ufshcd_wb_toggle() call and with this patch applied clk_scaling_lock is not held while ufshcd_wb_toggle() is called. I'm missing an explanation of why this change is safe. Thanks, Bart.
diff --git a/drivers/ufs/core/ufshcd.c b/drivers/ufs/core/ufshcd.c index c7b337480e3e..209089bd8085 100644 --- a/drivers/ufs/core/ufshcd.c +++ b/drivers/ufs/core/ufshcd.c @@ -1249,12 +1249,10 @@ 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 +1269,7 @@ 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 +1298,15 @@ 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); + 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); + return ret; }
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: Because ufshcd_wb_toggle -> ufshcd_query_flag -> ufshcd_exec_dev_cmd will get read lock of clk_scaling_lock, so ufshcd_devfreq_scale can release read lock before call ufshcd_wb_toggle. This patch only release write lock of clk_scaling_lock before ufshcd_wb_toggle. --- drivers/ufs/core/ufshcd.c | 22 +++++++++++----------- 1 file changed, 11 insertions(+), 11 deletions(-)