[{"id":3686730,"web_url":"http://patchwork.ozlabs.org/comment/3686730/","msgid":"<20260505215228.8E5B1C2BCB4@smtp.kernel.org>","list_archive_url":null,"date":"2026-05-05T21:52:28","subject":"Re: [PATCH v17 05/11] cxl: Limit CXL-CPER kfifo registration\n functions scope","submitter":{"id":93311,"url":"http://patchwork.ozlabs.org/api/people/93311/","name":null,"email":"sashiko-bot@kernel.org"},"content":"Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:\n- [High] Deadlock risk in CPER kfifo registration functions due to non-IRQ-safe spinlocks.\n--\n\ncommit 49bcf423cba32ca4c5cff3926588ae3d815744d1\nAuthor: Dan Williams \n\ncxl: Limit CXL-CPER kfifo registration functions scope\n\nThis commit replaces EXPORT_SYMBOL_NS_GPL with EXPORT_SYMBOL_FOR_MODULES\nfor CXL-CPER kfifo registration functions to improve access control. It also\nchanges the register and unregister functions to return void and adds\nsynchronous cancellation during unregistration.\n\n> diff --git a/drivers/acpi/apei/ghes.c b/drivers/acpi/apei/ghes.c\n> index 3236a3ce79d6b..dd0a073af93c3 100644\n> --- a/drivers/acpi/apei/ghes.c\n> +++ b/drivers/acpi/apei/ghes.c\n> @@ -778,33 +778,34 @@ static void cxl_cper_post_prot_err(struct cxl_cper_sec_prot_err *prot_err,\n> #endif\n> }\n> \n> -int cxl_cper_register_prot_err_work(struct work_struct *work)\n> +void cxl_cper_register_prot_err_work(struct work_struct *work)\n> {\n> -\tif (cxl_cper_prot_err_work)\n> -\t\treturn -EINVAL;\n> -\n> \tguard(spinlock)(&cxl_cper_prot_err_work_lock);\n\nCould this lead to a deadlock with the hardware error interrupt handler?\n\nLooking at cxl_cper_post_prot_err() which is called from GHES error handling\nin hard IRQ context, it uses the IRQ-safe variant to acquire the same lock:\n\n\tguard(spinlock_irqsave)(&cxl_cper_prot_err_work_lock);\n\nSince guard(spinlock) in cxl_cper_register_prot_err_work() leaves local\ninterrupts enabled, if a hardware error interrupt occurs on the same CPU\nwhile the lock is held here, the interrupt handler will execute\ncxl_cper_post_prot_err() and spin indefinitely waiting for the lock.\n\nWould it be better to use guard(spinlock_irqsave) here and in the unregister\nfunction to prevent this lockup?\n\n> +\tWARN_ONCE(cxl_cper_prot_err_work,\n> +\t\t \"CPER-CXL kfifo consumer already registered\\n\");\n> \tcxl_cper_prot_err_work = work;\n> -\treturn 0;\n> }\n> -EXPORT_SYMBOL_NS_GPL(cxl_cper_register_prot_err_work, \"CXL\");\n> +EXPORT_SYMBOL_FOR_MODULES(cxl_cper_register_prot_err_work, \"cxl_core\");\n> \n> -int cxl_cper_unregister_prot_err_work(struct work_struct *work)\n> +void cxl_cper_unregister_prot_err_work(void)\n> {\n> -\tif (cxl_cper_prot_err_work != work)\n> -\t\treturn -EINVAL;\n> +\tstruct work_struct *work;\n> \n> -\tguard(spinlock)(&cxl_cper_prot_err_work_lock);\n> +\tspin_lock(&cxl_cper_prot_err_work_lock);\n\nSimilarly, does this need to be spin_lock_irqsave() to protect against\nthe same deadlock scenario?\n\n> +\twork = cxl_cper_prot_err_work;\n> \tcxl_cper_prot_err_work = NULL;\n> -\treturn 0;\n> +\tspin_unlock(&cxl_cper_prot_err_work_lock);\n> +\n> +\tif (work)\n> +\t\tcancel_work_sync(work);\n> }","headers":{"Return-Path":"\n ","X-Original-To":["incoming@patchwork.ozlabs.org","linux-pci@vger.kernel.org"],"Delivered-To":"patchwork-incoming@legolas.ozlabs.org","Authentication-Results":["legolas.ozlabs.org;\n\tdkim=pass (2048-bit key;\n unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256\n header.s=k20201202 header.b=sutITQFK;\n\tdkim-atps=neutral","legolas.ozlabs.org;\n spf=pass (sender SPF authorized) smtp.mailfrom=vger.kernel.org\n (client-ip=172.105.105.114; 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a=rsa-sha256; c=relaxed/simple; d=kernel.org;\n\ts=k20201202; t=1778017948;\n\tbh=QkCArRIELECPz1MzPTUCGcwOmLkdbVvcH6SbNnQVk4M=;\n\th=From:Subject:Reply-To:To:Cc:In-Reply-To:References:Date:From;\n\tb=sutITQFKa55HHJgIUMf7xgwPgPYLC+GhW7Uxrf2YCE00LFio1IOthPCB8NyI0rsYw\n\t j4nFVxpbiwMfqJxCAyvwIvb0bO7oqKmdTuu4CNwwFhZ/Q/uMJIOABspFjm0UFIqf3X\n\t h0PEMKrNfsYybcXh1Hq1gDtaBLoIEhaH5pnQ5qQ5YsmrMrBXdg5TmHcHM72N14Uj2N\n\t EuclYIYEOcUkcwGuFolx+mosELFGJfUEHZmGdqv11kJp2L9Q9fHDm9wN7j99lLYtsC\n\t T+R8mKXaG+SggVfpprpueKytJQmoKTNpqsV0JiFq1HjusD8iNqYFZ0xGwQTFZybXih\n\t b4irP3PyIY+bw==","From":"sashiko-bot@kernel.org","Subject":"Re: [PATCH v17 05/11] cxl: Limit CXL-CPER kfifo registration\n functions scope","Reply-To":"sashiko@lists.linux.dev","To":"\"Terry Bowman\" ","Cc":"linux-pci@vger.kernel.org","In-Reply-To":"<20260505173029.2718246-6-terry.bowman@amd.com>","References":"<20260505173029.2718246-6-terry.bowman@amd.com>","Content-Type":"text/plain; charset=utf-8","Content-Transfer-Encoding":"quoted-printable","Date":"Tue, 05 May 2026 21:52:28 +0000","Message-Id":"<20260505215228.8E5B1C2BCB4@smtp.kernel.org>","Precedence":"bulk","X-Mailing-List":"linux-pci@vger.kernel.org","List-Id":"","List-Subscribe":"","List-Unsubscribe":""}},{"id":3686745,"web_url":"http://patchwork.ozlabs.org/comment/3686745/","msgid":"<0a372718-a3ae-4c8c-94a6-6b6c334cab16@intel.com>","list_archive_url":null,"date":"2026-05-05T22:16:30","subject":"Re: [PATCH v17 05/11] cxl: Limit CXL-CPER kfifo registration\n functions scope","submitter":{"id":13225,"url":"http://patchwork.ozlabs.org/api/people/13225/","name":"Dave Jiang","email":"dave.jiang@intel.com"},"content":"On 5/5/26 10:30 AM, Terry Bowman wrote:\n> From: Dan Williams \n> \n> Some CPER functions used by CXL drivers are exported using the\n> EXPORT_SYMBOL_NS_GPL(fn, ns) macro. This doesn't provide compile time\n> enforcement or visibility of the consumers.\n> \n> This can be improved by using EXPORT_SYMBOL_FOR_MODULES() instead.\n> EXPORT_SYMBOL_FOR_MODULES() explicitly names the modules that can access\n> the function. This provides more precise control and visibility of symbol\n> exposure than the namespace macro. It also provides compile time checking.\n> \n> To improve control and clarity, update cxl_cper_register_prot_err_work(),\n> cxl_cper_unregister_prot_err_work(), and cxl_cper_prot_err_kfifo_get()\n> to use EXPORT_SYMBOL_FOR_MODULES(). Also, update the register and unregister\n> functions to return void type.\n> \n> Update the CPER kfifo unregister to cancel work while using\n> synchronization.\n> \n> Co-developed-by: Terry Bowman \n> Signed-off-by: Terry Bowman \n> Signed-off-by: Dan Williams \n\nReviewed-by: Dave Jiang \n\n\n> \n> ---\n> \n> Changes in v16->v17:\n> - Split from v16 02/10 (\"Update unregistration for AER-CXL and\n> CPER-CXL kfifos\"); AER-CXL half folded into v17 01/10.\n> - Convert exports to EXPORT_SYMBOL_FOR_MODULES(\"cxl_core\").\n> - Change register/unregister return type from int to void.\n> - Drop work_struct argument from cxl_cper_unregister_prot_err_work();\n> it now cancels its own work.\n> - Remove now-redundant cancel_work_sync() from cxl_ras_exit().\n> - Add WARN_ONCE() in cxl_cper_register_prot_err_work() for\n> double-registration.\n> ---\n> drivers/acpi/apei/ghes.c | 27 ++++++++++++++-------------\n> drivers/cxl/core/ras.c | 6 +++---\n> include/cxl/event.h | 10 ++++------\n> 3 files changed, 21 insertions(+), 22 deletions(-)\n> \n> diff --git a/drivers/acpi/apei/ghes.c b/drivers/acpi/apei/ghes.c\n> index 3236a3ce79d6..dd0a073af93c 100644\n> --- a/drivers/acpi/apei/ghes.c\n> +++ b/drivers/acpi/apei/ghes.c\n> @@ -778,33 +778,34 @@ static void cxl_cper_post_prot_err(struct cxl_cper_sec_prot_err *prot_err,\n> #endif\n> }\n> \n> -int cxl_cper_register_prot_err_work(struct work_struct *work)\n> +void cxl_cper_register_prot_err_work(struct work_struct *work)\n> {\n> -\tif (cxl_cper_prot_err_work)\n> -\t\treturn -EINVAL;\n> -\n> \tguard(spinlock)(&cxl_cper_prot_err_work_lock);\n> +\tWARN_ONCE(cxl_cper_prot_err_work,\n> +\t\t \"CPER-CXL kfifo consumer already registered\\n\");\n> \tcxl_cper_prot_err_work = work;\n> -\treturn 0;\n> }\n> -EXPORT_SYMBOL_NS_GPL(cxl_cper_register_prot_err_work, \"CXL\");\n> +EXPORT_SYMBOL_FOR_MODULES(cxl_cper_register_prot_err_work, \"cxl_core\");\n> \n> -int cxl_cper_unregister_prot_err_work(struct work_struct *work)\n> +void cxl_cper_unregister_prot_err_work(void)\n> {\n> -\tif (cxl_cper_prot_err_work != work)\n> -\t\treturn -EINVAL;\n> +\tstruct work_struct *work;\n> \n> -\tguard(spinlock)(&cxl_cper_prot_err_work_lock);\n> +\tspin_lock(&cxl_cper_prot_err_work_lock);\n> +\twork = cxl_cper_prot_err_work;\n> \tcxl_cper_prot_err_work = NULL;\n> -\treturn 0;\n> +\tspin_unlock(&cxl_cper_prot_err_work_lock);\n> +\n> +\tif (work)\n> +\t\tcancel_work_sync(work);\n> }\n> -EXPORT_SYMBOL_NS_GPL(cxl_cper_unregister_prot_err_work, \"CXL\");\n> +EXPORT_SYMBOL_FOR_MODULES(cxl_cper_unregister_prot_err_work, \"cxl_core\");\n> \n> int cxl_cper_prot_err_kfifo_get(struct cxl_cper_prot_err_work_data *wd)\n> {\n> \treturn kfifo_get(&cxl_cper_prot_err_fifo, wd);\n> }\n> -EXPORT_SYMBOL_NS_GPL(cxl_cper_prot_err_kfifo_get, \"CXL\");\n> +EXPORT_SYMBOL_FOR_MODULES(cxl_cper_prot_err_kfifo_get, \"cxl_core\");\n> \n> /* Room for 8 entries for each of the 4 event log queues */\n> #define CXL_CPER_FIFO_DEPTH 32\n> diff --git a/drivers/cxl/core/ras.c b/drivers/cxl/core/ras.c\n> index 56611da8357a..9193dac4e507 100644\n> --- a/drivers/cxl/core/ras.c\n> +++ b/drivers/cxl/core/ras.c\n> @@ -68,13 +68,13 @@ static DECLARE_WORK(cxl_cper_prot_err_work, cxl_cper_prot_err_work_fn);\n> \n> int cxl_ras_init(void)\n> {\n> -\treturn cxl_cper_register_prot_err_work(&cxl_cper_prot_err_work);\n> +\tcxl_cper_register_prot_err_work(&cxl_cper_prot_err_work);\n> +\treturn 0;\n> }\n> \n> void cxl_ras_exit(void)\n> {\n> -\tcxl_cper_unregister_prot_err_work(&cxl_cper_prot_err_work);\n> -\tcancel_work_sync(&cxl_cper_prot_err_work);\n> +\tcxl_cper_unregister_prot_err_work();\n> }\n> \n> static void cxl_dport_map_ras(struct cxl_dport *dport)\n> diff --git a/include/cxl/event.h b/include/cxl/event.h\n> index ff97fea718d2..51acedb0d683 100644\n> --- a/include/cxl/event.h\n> +++ b/include/cxl/event.h\n> @@ -289,8 +289,8 @@ struct cxl_cper_prot_err_work_data {\n> int cxl_cper_register_work(struct work_struct *work);\n> int cxl_cper_unregister_work(struct work_struct *work);\n> int cxl_cper_kfifo_get(struct cxl_cper_work_data *wd);\n> -int cxl_cper_register_prot_err_work(struct work_struct *work);\n> -int cxl_cper_unregister_prot_err_work(struct work_struct *work);\n> +void cxl_cper_register_prot_err_work(struct work_struct *work);\n> +void cxl_cper_unregister_prot_err_work(void);\n> int cxl_cper_prot_err_kfifo_get(struct cxl_cper_prot_err_work_data *wd);\n> #else\n> static inline int cxl_cper_register_work(struct work_struct *work)\n> @@ -306,13 +306,11 @@ static inline int cxl_cper_kfifo_get(struct cxl_cper_work_data *wd)\n> {\n> \treturn 0;\n> }\n> -static inline int cxl_cper_register_prot_err_work(struct work_struct *work)\n> +static inline void cxl_cper_register_prot_err_work(struct work_struct *work)\n> {\n> -\treturn 0;\n> }\n> -static inline int cxl_cper_unregister_prot_err_work(struct work_struct *work)\n> +static inline void cxl_cper_unregister_prot_err_work(void)\n> {\n> -\treturn 0;\n> }\n> static inline int cxl_cper_prot_err_kfifo_get(struct cxl_cper_prot_err_work_data *wd)\n> {","headers":{"Return-Path":"\n ","X-Original-To":["incoming@patchwork.ozlabs.org","linux-pci@vger.kernel.org"],"Delivered-To":"patchwork-incoming@legolas.ozlabs.org","Authentication-Results":["legolas.ozlabs.org;\n\tdkim=pass (2048-bit key;\n unprotected) header.d=intel.com header.i=@intel.com header.a=rsa-sha256\n header.s=Intel header.b=WKMhNlH2;\n\tdkim-atps=neutral","legolas.ozlabs.org;\n spf=pass (sender SPF authorized) smtp.mailfrom=vger.kernel.org\n (client-ip=172.234.253.10; helo=sea.lore.kernel.org;\n envelope-from=linux-pci+bounces-53806-incoming=patchwork.ozlabs.org@vger.kernel.org;\n receiver=patchwork.ozlabs.org)","smtp.subspace.kernel.org;\n\tdkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com\n header.b=\"WKMhNlH2\"","smtp.subspace.kernel.org;\n arc=none smtp.client-ip=192.198.163.15","smtp.subspace.kernel.org;\n dmarc=pass (p=none dis=none) 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alison.schofield@intel.com, djbw@kernel.org, bhelgaas@google.com,\n ming.li@zohomail.com, Smita.KoralahalliChannabasappa@amd.com,\n rrichter@amd.com, PradeepVineshReddy.Kodamati@amd.com, lukas@wunner.de,\n Benjamin.Cheatham@amd.com, sathyanarayanan.kuppuswamy@linux.intel.com,\n vishal.l.verma@intel.com, alucerop@amd.com, ira.weiny@intel.com,\n corbet@lwn.net, rafael@kernel.org, xueshuai@linux.alibaba.com,\n linux-cxl@vger.kernel.org","Cc":"linux-kernel@vger.kernel.org, linux-pci@vger.kernel.org,\n linux-acpi@vger.kernel.org, linux-doc@vger.kernel.org","References":"<20260505173029.2718246-1-terry.bowman@amd.com>\n <20260505173029.2718246-6-terry.bowman@amd.com>","Content-Language":"en-US","From":"Dave Jiang ","In-Reply-To":"<20260505173029.2718246-6-terry.bowman@amd.com>","Content-Type":"text/plain; charset=UTF-8","Content-Transfer-Encoding":"7bit"}},{"id":3687980,"web_url":"http://patchwork.ozlabs.org/comment/3687980/","msgid":"<20260507191450.45bc94c9@jic23-huawei>","list_archive_url":null,"date":"2026-05-07T18:14:50","subject":"Re: [PATCH v17 05/11] cxl: Limit CXL-CPER kfifo registration\n functions scope","submitter":{"id":10151,"url":"http://patchwork.ozlabs.org/api/people/10151/","name":"Jonathan Cameron","email":"jic23@kernel.org"},"content":"On Tue, 5 May 2026 12:30:23 -0500\nTerry Bowman wrote:\n\n> From: Dan Williams \n> \n> Some CPER functions used by CXL drivers are exported using the\n> EXPORT_SYMBOL_NS_GPL(fn, ns) macro. This doesn't provide compile time\n> enforcement or visibility of the consumers.\n> \n> This can be improved by using EXPORT_SYMBOL_FOR_MODULES() instead.\n> EXPORT_SYMBOL_FOR_MODULES() explicitly names the modules that can access\n> the function. This provides more precise control and visibility of symbol\n> exposure than the namespace macro. It also provides compile time checking.\n> \n> To improve control and clarity, update cxl_cper_register_prot_err_work(),\n> cxl_cper_unregister_prot_err_work(), and cxl_cper_prot_err_kfifo_get()\n> to use EXPORT_SYMBOL_FOR_MODULES(). Also, update the register and unregister\n> functions to return void type.\n> \n> Update the CPER kfifo unregister to cancel work while using\n> synchronization.\n> \n> Co-developed-by: Terry Bowman \n> Signed-off-by: Terry Bowman \n> Signed-off-by: Dan Williams \nOne suggestion on simplifying the code by removing any assumption that\ncxl_ras_init() can fail.\n\n\n> diff --git a/drivers/cxl/core/ras.c b/drivers/cxl/core/ras.c\n> index 56611da8357a..9193dac4e507 100644\n> --- a/drivers/cxl/core/ras.c\n> +++ b/drivers/cxl/core/ras.c\n> @@ -68,13 +68,13 @@ static DECLARE_WORK(cxl_cper_prot_err_work, cxl_cper_prot_err_work_fn);\n> \n> int cxl_ras_init(void)\n> {\n> -\treturn cxl_cper_register_prot_err_work(&cxl_cper_prot_err_work);\n> +\tcxl_cper_register_prot_err_work(&cxl_cper_prot_err_work);\n> +\treturn 0;\n\nI'm lazy and haven't read on, but if this never gains a failure\npath can we change the signature whilst we are here to stop\npretending it does?\n\n> }","headers":{"Return-Path":"\n ","X-Original-To":["incoming@patchwork.ozlabs.org","linux-pci@vger.kernel.org"],"Delivered-To":"patchwork-incoming@legolas.ozlabs.org","Authentication-Results":["legolas.ozlabs.org;\n\tdkim=pass (2048-bit key;\n unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256\n header.s=k20201202 header.b=odT3AOTy;\n\tdkim-atps=neutral","legolas.ozlabs.org;\n spf=pass (sender SPF authorized) smtp.mailfrom=vger.kernel.org\n (client-ip=172.234.253.10; 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