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Date: Sun, 25 Oct 2020 23:13:13 -0700 From: Jaegeuk Kim <jaegeuk@...nel.org> To: Can Guo <cang@...eaurora.org> Cc: linux-kernel@...r.kernel.org, linux-scsi@...r.kernel.org, linux-f2fs-devel@...ts.sourceforge.net, kernel-team@...roid.com, alim.akhtar@...sung.com, avri.altman@....com, bvanassche@....org Subject: Re: [PATCH v3 1/5] scsi: ufs: atomic update for clkgating_enable On 10/26, Can Guo wrote: > On 2020-10-24 23:06, Jaegeuk Kim wrote: > > From: Jaegeuk Kim <jaegeuk@...gle.com> > > > > When giving a stress test which enables/disables clkgating, we hit > > device > > timeout sometimes. This patch avoids subtle racy condition to address > > it. > > > > If we use __ufshcd_release(), I've seen that gate_work can be called in > > parallel > > with ungate_work, which results in UFS timeout when doing hibern8. > > Should avoid it. > > > > I don't understand this comment. gate_work and ungate_work are queued on > an ordered workqueue and an ordered workqueue executes at most one work item > at any given time in the queued order. How can the two run in parallel? When I hit UFS stuck, I saw this by clkgating tracepoint. - REQ_CLK_OFF - CLKS_OFF - REQ_CLK_OFF - REQ_CLKS_ON .. By using active_req, I don't see any problem. > > Thanks, > > Can Guo. > > > Signed-off-by: Jaegeuk Kim <jaegeuk@...gle.com> > > --- > > drivers/scsi/ufs/ufshcd.c | 12 ++++++------ > > 1 file changed, 6 insertions(+), 6 deletions(-) > > > > diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c > > index b8f573a02713..e0b479f9eb8a 100644 > > --- a/drivers/scsi/ufs/ufshcd.c > > +++ b/drivers/scsi/ufs/ufshcd.c > > @@ -1807,19 +1807,19 @@ static ssize_t > > ufshcd_clkgate_enable_store(struct device *dev, > > return -EINVAL; > > > > value = !!value; > > + > > + spin_lock_irqsave(hba->host->host_lock, flags); > > if (value == hba->clk_gating.is_enabled) > > goto out; > > > > - if (value) { > > - ufshcd_release(hba); > > - } else { > > - spin_lock_irqsave(hba->host->host_lock, flags); > > + if (value) > > + hba->clk_gating.active_reqs--; > > + else > > hba->clk_gating.active_reqs++; > > - spin_unlock_irqrestore(hba->host->host_lock, flags); > > - } > > > > hba->clk_gating.is_enabled = value; > > out: > > + spin_unlock_irqrestore(hba->host->host_lock, flags); > > return count; > > }
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