From: Can Guo <cang@codeaurora.org> To: Jaegeuk Kim <jaegeuk@kernel.org> Cc: linux-kernel@vger.kernel.org, linux-scsi@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net, kernel-team@android.com, alim.akhtar@samsung.com, avri.altman@wdc.com, bvanassche@acm.org Subject: Re: [PATCH v3 1/5] scsi: ufs: atomic update for clkgating_enable Date: Mon, 26 Oct 2020 14:43:53 +0800 [thread overview] Message-ID: <6c029b64cb4d78e7624bc896f9c9f16d@codeaurora.org> (raw) In-Reply-To: <20201026061313.GA2517102@google.com> On 2020-10-26 14:13, Jaegeuk Kim wrote: > On 10/26, Can Guo wrote: >> On 2020-10-24 23:06, Jaegeuk Kim wrote: >> > From: Jaegeuk Kim <jaegeuk@google.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 > .. > I don't see how can you tell that the two works are running in parallel just from above trace. May I know what is the exact error by "UFS timeout when doing hibern8"? By using __ufshcd_release() here, I do see one potential issue if your test quickly toggles on/off of clk_gating - disable it, enable it, disable it and enable it, which will cause that __ufshcd_release() being called twice, meaning we queue two gate_works back to back. So can you try below code and let me know if it helps or not? I am OK with your current change, but I would like to understand the problem. Thanks. diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c index 1791bce..3eee438 100644 --- a/drivers/scsi/ufs/ufshcd.c +++ b/drivers/scsi/ufs/ufshcd.c @@ -2271,6 +2271,8 @@ static void ufshcd_gate_work(struct work_struct *work) unsigned long flags; spin_lock_irqsave(hba->host->host_lock, flags); + if (hba->clk_gating.state == CLKS_OFF) + goto rel_lock; /* * In case you are here to cancel this work the gating state * would be marked as REQ_CLKS_ON. In this case save time by Regards, Can Guo. > By using active_req, I don't see any problem. > >> >> Thanks, >> >> Can Guo. >> >> > Signed-off-by: Jaegeuk Kim <jaegeuk@google.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; >> > }
WARNING: multiple messages have this Message-ID (diff)
From: Can Guo <cang@codeaurora.org> To: Jaegeuk Kim <jaegeuk@kernel.org> Cc: bvanassche@acm.org, linux-scsi@vger.kernel.org, linux-kernel@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net, avri.altman@wdc.com, alim.akhtar@samsung.com, kernel-team@android.com Subject: Re: [f2fs-dev] [PATCH v3 1/5] scsi: ufs: atomic update for clkgating_enable Date: Mon, 26 Oct 2020 14:43:53 +0800 [thread overview] Message-ID: <6c029b64cb4d78e7624bc896f9c9f16d@codeaurora.org> (raw) In-Reply-To: <20201026061313.GA2517102@google.com> On 2020-10-26 14:13, Jaegeuk Kim wrote: > On 10/26, Can Guo wrote: >> On 2020-10-24 23:06, Jaegeuk Kim wrote: >> > From: Jaegeuk Kim <jaegeuk@google.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 > .. > I don't see how can you tell that the two works are running in parallel just from above trace. May I know what is the exact error by "UFS timeout when doing hibern8"? By using __ufshcd_release() here, I do see one potential issue if your test quickly toggles on/off of clk_gating - disable it, enable it, disable it and enable it, which will cause that __ufshcd_release() being called twice, meaning we queue two gate_works back to back. So can you try below code and let me know if it helps or not? I am OK with your current change, but I would like to understand the problem. Thanks. diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c index 1791bce..3eee438 100644 --- a/drivers/scsi/ufs/ufshcd.c +++ b/drivers/scsi/ufs/ufshcd.c @@ -2271,6 +2271,8 @@ static void ufshcd_gate_work(struct work_struct *work) unsigned long flags; spin_lock_irqsave(hba->host->host_lock, flags); + if (hba->clk_gating.state == CLKS_OFF) + goto rel_lock; /* * In case you are here to cancel this work the gating state * would be marked as REQ_CLKS_ON. In this case save time by Regards, Can Guo. > By using active_req, I don't see any problem. > >> >> Thanks, >> >> Can Guo. >> >> > Signed-off-by: Jaegeuk Kim <jaegeuk@google.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; >> > } _______________________________________________ Linux-f2fs-devel mailing list Linux-f2fs-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel
next prev parent reply other threads:[~2020-10-26 6:43 UTC|newest] Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top 2020-10-24 15:06 [UFS v3] UFS fixes Jaegeuk Kim 2020-10-24 15:06 ` [f2fs-dev] " Jaegeuk Kim 2020-10-24 15:06 ` [PATCH v3 1/5] scsi: ufs: atomic update for clkgating_enable Jaegeuk Kim 2020-10-24 15:06 ` [f2fs-dev] " Jaegeuk Kim 2020-10-26 3:28 ` Can Guo 2020-10-26 3:28 ` [f2fs-dev] " Can Guo 2020-10-26 6:13 ` Jaegeuk Kim 2020-10-26 6:13 ` [f2fs-dev] " Jaegeuk Kim 2020-10-26 6:43 ` Can Guo [this message] 2020-10-26 6:43 ` Can Guo 2020-10-26 19:48 ` Jaegeuk Kim 2020-10-26 19:48 ` [f2fs-dev] " Jaegeuk Kim 2020-10-27 2:44 ` Can Guo 2020-10-27 2:44 ` [f2fs-dev] " Can Guo 2020-10-24 15:06 ` [PATCH v3 2/5] scsi: ufs: clear UAC for FFU and RPMB LUNs Jaegeuk Kim 2020-10-24 15:06 ` [f2fs-dev] " Jaegeuk Kim 2020-10-26 18:25 ` asutoshd 2020-10-26 18:25 ` [f2fs-dev] " asutoshd 2020-10-26 19:43 ` Jaegeuk Kim 2020-10-26 19:43 ` [f2fs-dev] " Jaegeuk Kim 2020-10-27 17:48 ` kernel test robot 2020-10-27 17:48 ` kernel test robot 2020-10-24 15:06 ` [PATCH v3 3/5] scsi: ufs: use WQ_HIGHPRI for gating work Jaegeuk Kim 2020-10-24 15:06 ` [f2fs-dev] " Jaegeuk Kim 2020-10-26 18:27 ` asutoshd 2020-10-26 18:27 ` [f2fs-dev] " asutoshd 2020-10-24 15:06 ` [PATCH v3 4/5] scsi: add more contexts in the ufs tracepoints Jaegeuk Kim 2020-10-24 15:06 ` [f2fs-dev] " Jaegeuk Kim 2020-10-24 15:06 ` [PATCH v3 5/5] scsi: ufs: fix clkgating on/off correctly Jaegeuk Kim 2020-10-24 15:06 ` [f2fs-dev] " Jaegeuk Kim 2020-10-26 18:33 ` asutoshd 2020-10-26 18:33 ` [f2fs-dev] " asutoshd
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