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Fri, 29 Sep 2023 11:40:33 -0700 (PDT) X-Google-Smtp-Source: AGHT+IHwASWCl5cZ1JPkXdR7F8OEtFHMXuQkyf5k8zTIL92lAUzma1wamU3ODUvk5iZJIg+H+IXjAg== X-Received: by 2002:ac8:7d91:0:b0:419:4f1e:7ea9 with SMTP id c17-20020ac87d91000000b004194f1e7ea9mr6172362qtd.3.1696012832708; Fri, 29 Sep 2023 11:40:32 -0700 (PDT) Received: from fedora ([107.171.218.122]) by smtp.gmail.com with ESMTPSA id g11-20020ac8124b000000b004181234dd1dsm955698qtj.96.2023.09.29.11.40.31 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 29 Sep 2023 11:40:32 -0700 (PDT) Date: Fri, 29 Sep 2023 14:40:30 -0400 From: Adrien Thierry To: Deepti Jaggi Cc: james.morse@arm.com, mchehab@kernel.org, rric@kernel.org, bp@alien8.de, tony.luck@intel.com, linux-edac@vger.kernel.org, linux-kernel@vger.kernel.org, kernel@quicinc.com, quic_psodagud@quicinc.com Subject: Re: [PATCH] EDAC/device: Add sysfs notification for UE,CE count change Message-ID: References: <20230731220059.28474-1-quic_djaggi@quicinc.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230731220059.28474-1-quic_djaggi@quicinc.com> Precedence: bulk List-ID: X-Mailing-List: linux-edac@vger.kernel.org Hi Deepti, On Mon, Jul 31, 2023 at 03:00:59PM -0700, Deepti Jaggi wrote: > A daemon running in user space collects information on correctable > and uncorrectable errors from EDAC driver by reading corresponding > sysfs entries and takes appropriate action. > This patch adds support for user space daemon to wait on poll() until > the sysfs entries for UE count and CE count change and then read updated > counts instead of continuously monitoring the sysfs entries for > any changes. > > Signed-off-by: Deepti Jaggi > --- > drivers/edac/edac_device.c | 16 ++++++++++++++++ > drivers/edac/edac_device.h | 8 ++++++++ > drivers/edac/edac_device_sysfs.c | 20 ++++++++++++++++++++ > 3 files changed, 44 insertions(+) > > diff --git a/drivers/edac/edac_device.c b/drivers/edac/edac_device.c > index 8c4d947fb848..7b7aec4da6b9 100644 > --- a/drivers/edac/edac_device.c > +++ b/drivers/edac/edac_device.c > @@ -587,12 +587,20 @@ void edac_device_handle_ce_count(struct edac_device_ctl_info *edac_dev, > if (instance->nr_blocks > 0) { > block = instance->blocks + block_nr; > block->counters.ce_count += count; > + > + /* Notify block sysfs attribute change */ > + if (block->kn_ce) > + sysfs_notify_dirent(block->kn_ce); > } > > /* Propagate the count up the 'totals' tree */ > instance->counters.ce_count += count; > edac_dev->counters.ce_count += count; > > + /* Notify instance sysfs attribute change */ > + if (instance->kn_ce) > + sysfs_notify_dirent(instance->kn_ce); > + > if (edac_device_get_log_ce(edac_dev)) > edac_device_printk(edac_dev, KERN_WARNING, > "CE: %s instance: %s block: %s count: %d '%s'\n", > @@ -633,12 +641,20 @@ void edac_device_handle_ue_count(struct edac_device_ctl_info *edac_dev, > if (instance->nr_blocks > 0) { > block = instance->blocks + block_nr; > block->counters.ue_count += count; > + > + /* Notify block sysfs attribute change */ > + if (block->kn_ue) > + sysfs_notify_dirent(block->kn_ue); > } > > /* Propagate the count up the 'totals' tree */ > instance->counters.ue_count += count; > edac_dev->counters.ue_count += count; > > + /* Notify instance sysfs attribute change */ > + if (instance->kn_ue) > + sysfs_notify_dirent(instance->kn_ue); > + > if (edac_device_get_log_ue(edac_dev)) > edac_device_printk(edac_dev, KERN_EMERG, > "UE: %s instance: %s block: %s count: %d '%s'\n", > diff --git a/drivers/edac/edac_device.h b/drivers/edac/edac_device.h > index fc2d2c218064..459514ea549e 100644 > --- a/drivers/edac/edac_device.h > +++ b/drivers/edac/edac_device.h > @@ -127,6 +127,10 @@ struct edac_device_block { > > /* edac sysfs device control */ > struct kobject kobj; > + > + /* kern fs node for block ue_count and ce count attributes*/ > + struct kernfs_node *kn_ue; > + struct kernfs_node *kn_ce; > }; > > /* device instance control structure */ > @@ -141,6 +145,10 @@ struct edac_device_instance { > > /* edac sysfs device control */ > struct kobject kobj; > + > + /* kern fs node for block ue_count and ce count attributes*/ > + struct kernfs_node *kn_ue; > + struct kernfs_node *kn_ce; > }; > > > diff --git a/drivers/edac/edac_device_sysfs.c b/drivers/edac/edac_device_sysfs.c > index 5e7593753799..d1e04a9296c7 100644 > --- a/drivers/edac/edac_device_sysfs.c > +++ b/drivers/edac/edac_device_sysfs.c > @@ -562,6 +562,13 @@ static int edac_device_create_block(struct edac_device_ctl_info *edac_dev, > } > kobject_uevent(&block->kobj, KOBJ_ADD); > > + /* > + * Save kernfs pointer for ue count and ce count > + * to notify from any context when attributes change > + */ > + block->kn_ue = sysfs_get_dirent(block->kobj.sd, "ue_count"); > + block->kn_ce = sysfs_get_dirent(block->kobj.sd, "ce_count"); > + > return 0; > > /* Error unwind stack */ > @@ -594,6 +601,9 @@ static void edac_device_delete_block(struct edac_device_ctl_info *edac_dev, > } > } > > + block->kn_ue = NULL; > + block->kn_ce = NULL; > + Isn't there a possibility for a race condition here? It seems to me that between the moment the attribute files are removed with sysfs_remove_file() a few lines above, and the moment block->kn_ue and block->kn_ce are nulled, sysfs_notify_dirent() can be called from edac_device_handle_ce_count() with an block->kn_ce that refers to a deleted file. > /* unregister this block's kobject, SEE: > * edac_device_ctrl_block_release() callback operation > */ > @@ -660,6 +670,13 @@ static int edac_device_create_instance(struct edac_device_ctl_info *edac_dev, > edac_dbg(4, "Registered instance %d '%s' kobject\n", > idx, instance->name); > > + /* > + * Save kernfs pointer for ue count and ce count > + * to notify from any context when attributes change > + */ > + instance->kn_ue = sysfs_get_dirent(instance->kobj.sd, "ue_count"); > + instance->kn_ce = sysfs_get_dirent(instance->kobj.sd, "ce_count"); > + > return 0; > > /* error unwind stack */ > @@ -682,6 +699,9 @@ static void edac_device_delete_instance(struct edac_device_ctl_info *edac_dev, > > instance = &edac_dev->instances[idx]; > > + instance->kn_ue = NULL; > + instance->kn_ce = NULL; > + > /* unregister all blocks in this instance */ > for (i = 0; i < instance->nr_blocks; i++) > edac_device_delete_block(edac_dev, &instance->blocks[i]); > -- > 2.31.1 > Best, Adrien