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Tue, 27 Oct 2020 02:44:15 GMT Received: by smtp.codeaurora.org (Postfix, from userid 1001) id D3B19C43382; Tue, 27 Oct 2020 02:44:15 +0000 (UTC) Received: from mail.codeaurora.org (localhost.localdomain [127.0.0.1]) (using TLSv1 with cipher ECDHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) (Authenticated sender: cang) by smtp.codeaurora.org (Postfix) with ESMTPSA id B4407C433F0; Tue, 27 Oct 2020 02:44:14 +0000 (UTC) MIME-Version: 1.0 Date: Tue, 27 Oct 2020 10:44:14 +0800 From: Can Guo To: Jaegeuk Kim In-Reply-To: <20201026194817.GA359340@google.com> References: <20201024150646.1790529-1-jaegeuk@kernel.org> <20201024150646.1790529-2-jaegeuk@kernel.org> <68cf5fe17691653f07544db5fe390c97@codeaurora.org> <20201026061313.GA2517102@google.com> <6c029b64cb4d78e7624bc896f9c9f16d@codeaurora.org> <20201026194817.GA359340@google.com> Message-ID: <63bb653fe0a26f092426945a8af1aba5@codeaurora.org> X-Sender: cang@codeaurora.org User-Agent: Roundcube Webmail/1.3.9 X-Headers-End: 1kXEyP-00F1hr-LX Subject: Re: [f2fs-dev] [PATCH v3 1/5] scsi: ufs: atomic update for clkgating_enable X-BeenThere: linux-f2fs-devel@lists.sourceforge.net X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , 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 Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Errors-To: linux-f2fs-devel-bounces@lists.sourceforge.net On 2020-10-27 03:48, Jaegeuk Kim wrote: > On 10/26, Can Guo wrote: >> 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 >> > > > >> > > > 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 > > This doesn't help. So, I checked this back again, and, like what you > said, now > suspect __ufshcd_release() which changed state to REQ_CLKS_OFF on > CLKS_OFF. > Aha, sorry that I gave the right analysis but wrong fix - my check won't help since it is checking CLKS_OFF, but at that moment it has become CLKS_REQ_OFF. Your fix is fulfiling the right purpose. Thanks, Can Guo. > With the below change, I can see the issue anymore. Let me send v4. > > --- > drivers/scsi/ufs/ufshcd.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c > index b8f573a02713..cc8d5f0c3fdc 100644 > --- a/drivers/scsi/ufs/ufshcd.c > +++ b/drivers/scsi/ufs/ufshcd.c > @@ -1745,7 +1745,8 @@ static void __ufshcd_release(struct ufs_hba *hba) > if (hba->clk_gating.active_reqs || hba->clk_gating.is_suspended || > hba->ufshcd_state != UFSHCD_STATE_OPERATIONAL || > ufshcd_any_tag_in_use(hba) || hba->outstanding_tasks || > - hba->active_uic_cmd || hba->uic_async_done) > + hba->active_uic_cmd || hba->uic_async_done || > + hba->clk_gating.state == CLKS_OFF) > return; > > hba->clk_gating.state = REQ_CLKS_OFF; > -- > 2.29.0.rc1.297.gfa9743e501-goog > > >> >> Regards, >> >> Can Guo. >> >> > By using active_req, I don't see any problem. >> > >> > > >> > > Thanks, >> > > >> > > Can Guo. >> > > >> > > > Signed-off-by: Jaegeuk Kim >> > > > --- >> > > > 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