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[2.34.24.178]) by smtp.gmail.com with ESMTPSA id v7-20020ac87487000000b0041950c7f6d8sm4430101qtq.60.2023.11.22.06.33.05 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 22 Nov 2023 06:33:07 -0800 (PST) From: Marco Pagani To: Moritz Fischer , Wu Hao , Xu Yilun , Tom Rix , Greg Kroah-Hartman Cc: Marco Pagani , linux-kernel@vger.kernel.org, linux-fpga@vger.kernel.org Subject: [RFC PATCH 1/2] fpga: add a module owner field to fpga_manager and fpga_manager_ops Date: Wed, 22 Nov 2023 15:32:51 +0100 Message-ID: <20231122143252.181680-2-marpagan@redhat.com> X-Mailer: git-send-email 2.42.0 In-Reply-To: <20231122143252.181680-1-marpagan@redhat.com> References: <20231122143252.181680-1-marpagan@redhat.com> Precedence: bulk X-Mailing-List: linux-fpga@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Add a module *owner field to the fpga_manager_ops and fpga_manager structs to protect the fpga manager against the unloading of the low-level control module while someone is holding a reference to the manager device. Low-level control modules should statically set the owner field of the fpga_manager_ops struct to THIS_MODULE. Then, when the manager is registered using fpga_mgr_register(), the value is copied into the owner field of the fpga_manager struct (that contains the device context). In this way, the manager can later use it in fpga_mgr_get() to take the low-level module's refcount. To prevent races while unloading the low-level control module, the fpga_mgr_get() and fpga_mgr_put() methods are protected with a mutex. Other changes: moved put_device() form __fpga_mgr_get() to fpga_mgr_get() and of_fpga_mgr_get() to improve code clarity. Fixes: 654ba4cc0f3e ("fpga manager: ensure lifetime with of_fpga_mgr_get") Signed-off-by: Marco Pagani --- drivers/fpga/fpga-mgr.c | 56 +++++++++++++++++++++++++---------- include/linux/fpga/fpga-mgr.h | 4 +++ 2 files changed, 44 insertions(+), 16 deletions(-) diff --git a/drivers/fpga/fpga-mgr.c b/drivers/fpga/fpga-mgr.c index 06651389c592..f76be7e2f722 100644 --- a/drivers/fpga/fpga-mgr.c +++ b/drivers/fpga/fpga-mgr.c @@ -21,6 +21,8 @@ static DEFINE_IDA(fpga_mgr_ida); static const struct class fpga_mgr_class; +static DEFINE_MUTEX(mgr_lock); + struct fpga_mgr_devres { struct fpga_manager *mgr; }; @@ -667,17 +669,15 @@ ATTRIBUTE_GROUPS(fpga_mgr); static struct fpga_manager *__fpga_mgr_get(struct device *dev) { struct fpga_manager *mgr; + struct module *owner; mgr = to_fpga_manager(dev); + owner = mgr->owner; - if (!try_module_get(dev->parent->driver->owner)) - goto err_dev; + if (owner && !try_module_get(owner)) + mgr = ERR_PTR(-ENODEV); return mgr; - -err_dev: - put_device(dev); - return ERR_PTR(-ENODEV); } static int fpga_mgr_dev_match(struct device *dev, const void *data) @@ -693,12 +693,22 @@ static int fpga_mgr_dev_match(struct device *dev, const void *data) */ struct fpga_manager *fpga_mgr_get(struct device *dev) { - struct device *mgr_dev = class_find_device(&fpga_mgr_class, NULL, dev, - fpga_mgr_dev_match); + struct fpga_manager *mgr = ERR_PTR(-ENODEV); + struct device *mgr_dev; + + mutex_lock(&mgr_lock); + + mgr_dev = class_find_device(&fpga_mgr_class, NULL, dev, fpga_mgr_dev_match); if (!mgr_dev) - return ERR_PTR(-ENODEV); + goto out; + + mgr = __fpga_mgr_get(mgr_dev); + if (IS_ERR(mgr)) + put_device(mgr_dev); - return __fpga_mgr_get(mgr_dev); +out: + mutex_unlock(&mgr_lock); + return mgr; } EXPORT_SYMBOL_GPL(fpga_mgr_get); @@ -711,13 +721,22 @@ EXPORT_SYMBOL_GPL(fpga_mgr_get); */ struct fpga_manager *of_fpga_mgr_get(struct device_node *node) { - struct device *dev; + struct fpga_manager *mgr = ERR_PTR(-ENODEV); + struct device *mgr_dev; + + mutex_lock(&mgr_lock); + + mgr_dev = class_find_device_by_of_node(&fpga_mgr_class, node); + if (!mgr_dev) + goto out; - dev = class_find_device_by_of_node(&fpga_mgr_class, node); - if (!dev) - return ERR_PTR(-ENODEV); + mgr = __fpga_mgr_get(mgr_dev); + if (IS_ERR(mgr)) + put_device(mgr_dev); - return __fpga_mgr_get(dev); +out: + mutex_unlock(&mgr_lock); + return mgr; } EXPORT_SYMBOL_GPL(of_fpga_mgr_get); @@ -727,8 +746,12 @@ EXPORT_SYMBOL_GPL(of_fpga_mgr_get); */ void fpga_mgr_put(struct fpga_manager *mgr) { - module_put(mgr->dev.parent->driver->owner); + mutex_lock(&mgr_lock); + + module_put(mgr->owner); put_device(&mgr->dev); + + mutex_unlock(&mgr_lock); } EXPORT_SYMBOL_GPL(fpga_mgr_put); @@ -806,6 +829,7 @@ fpga_mgr_register_full(struct device *parent, const struct fpga_manager_info *in mgr->name = info->name; mgr->mops = info->mops; + mgr->owner = info->mops->owner; mgr->priv = info->priv; mgr->compat_id = info->compat_id; diff --git a/include/linux/fpga/fpga-mgr.h b/include/linux/fpga/fpga-mgr.h index 54f63459efd6..eaf6e072dbc0 100644 --- a/include/linux/fpga/fpga-mgr.h +++ b/include/linux/fpga/fpga-mgr.h @@ -162,6 +162,7 @@ struct fpga_manager_info { * @write_complete: set FPGA to operating state after writing is done * @fpga_remove: optional: Set FPGA into a specific state during driver remove * @groups: optional attribute groups. + * @owner: owner module. * * fpga_manager_ops are the low level functions implemented by a specific * fpga manager driver. The optional ones are tested for NULL before being @@ -184,6 +185,7 @@ struct fpga_manager_ops { struct fpga_image_info *info); void (*fpga_remove)(struct fpga_manager *mgr); const struct attribute_group **groups; + struct module *owner; }; /* FPGA manager status: Partial/Full Reconfiguration errors */ @@ -201,6 +203,7 @@ struct fpga_manager_ops { * @state: state of fpga manager * @compat_id: FPGA manager id for compatibility check. * @mops: pointer to struct of fpga manager ops + * @owner: owner module. * @priv: low level driver private date */ struct fpga_manager { @@ -210,6 +213,7 @@ struct fpga_manager { enum fpga_mgr_states state; struct fpga_compat_id *compat_id; const struct fpga_manager_ops *mops; + struct module *owner; void *priv; };