From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id F3487139574 for ; Thu, 7 Mar 2024 13:39:53 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.133.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1709818796; cv=none; b=YBOVGzh6AbPQYyYkI2RJqAejBeI5MFgs/CCsxSdlLe4JcmBprJIYLRAk3+pxyWo3oAyvvLL1etHOhW9HzByImdxSesUvon0bptQNsJxDHpWNoPS1D31Q3NO7NdVw8DRxYNAXZhWI6aRjP91tQkfhRRsJodDmlbxm9j+pBNmVMF0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1709818796; c=relaxed/simple; bh=lNA1D4PxgTE+BH5Xs2JJugSoGU2banGwahprvTGRSvs=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=tqC1AzmzXBtodz7hxXIUND+BkdIpm0PBy4Pej+MACOYc5e190/5C+oht5sA87qFClyPA0W7do294sX2JmDeYSFtmJw9JPLdU/8G4ekPq/uGLZ7Cp9uz5pfv9KA4Od4auIKS+y6CG/ekdNlxIwEhZWDXxU1UFB/Ps+PYuYwThgQ8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=D5YqfRFS; arc=none smtp.client-ip=170.10.133.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="D5YqfRFS" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1709818793; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=112pI+gt3JMCgKzIzUNSwArv3bdYT5A5xYg70+5/nCY=; b=D5YqfRFSQihjhvSRKnbpjEPDtCbp51UkbW9vQHYe+0aMeRoo2MIS7gOXHmxqw81/lmGg+l BrJwUlXAOY31UUyvD+t7WYDoMonOv05MfOteaHrq+YMTugJWboSQ9rRN7ncq1xpagdEdYy Ak+t2Zd1gfQaDS0fCQpD33zpXRnfRAA= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-286-PhGOQ0k9Pra5YEfCRg8aGQ-1; Thu, 07 Mar 2024 08:39:50 -0500 X-MC-Unique: PhGOQ0k9Pra5YEfCRg8aGQ-1 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.rdu2.redhat.com [10.11.54.7]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 1EA19101A523; Thu, 7 Mar 2024 13:39:49 +0000 (UTC) Received: from [10.22.17.9] (unknown [10.22.17.9]) by smtp.corp.redhat.com (Postfix) with ESMTP id 5BB371C0653F; Thu, 7 Mar 2024 13:39:47 +0000 (UTC) Message-ID: <3d95ab40-2df5-4988-87be-568a628a0561@redhat.com> Date: Thu, 7 Mar 2024 08:39:46 -0500 Precedence: bulk X-Mailing-List: linux-leds@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v5 02/10] locking/mutex: introduce devm_mutex_init Content-Language: en-US To: =?UTF-8?Q?Marek_Beh=C3=BAn?= , George Stark Cc: andy.shevchenko@gmail.com, pavel@ucw.cz, lee@kernel.org, vadimp@nvidia.com, mpe@ellerman.id.au, npiggin@gmail.com, christophe.leroy@csgroup.eu, hdegoede@redhat.com, mazziesaccount@gmail.com, peterz@infradead.org, mingo@redhat.com, will@kernel.org, boqun.feng@gmail.com, nikitos.tr@gmail.com, kabel@kernel.org, linux-leds@vger.kernel.org, linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, kernel@salutedevices.com References: <20240307024034.1548605-1-gnstark@salutedevices.com> <20240307024034.1548605-3-gnstark@salutedevices.com> <20240307095639.b6utkbzr36liuu3p@kandell> From: Waiman Long In-Reply-To: <20240307095639.b6utkbzr36liuu3p@kandell> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.7 On 3/7/24 04:56, Marek Behún wrote: > On Thu, Mar 07, 2024 at 05:40:26AM +0300, George Stark wrote: >> Using of devm API leads to a certain order of releasing resources. >> So all dependent resources which are not devm-wrapped should be deleted >> with respect to devm-release order. Mutex is one of such objects that >> often is bound to other resources and has no own devm wrapping. >> Since mutex_destroy() actually does nothing in non-debug builds >> frequently calling mutex_destroy() is just ignored which is safe for now >> but wrong formally and can lead to a problem if mutex_destroy() will be >> extended so introduce devm_mutex_init() >> >> Signed-off-by: George Stark >> Signed-off-by: Christophe Leroy >> --- >> Hello Christophe. Hope you don't mind I put you SoB tag because you helped alot >> to make this patch happen. >> >> include/linux/mutex.h | 13 +++++++++++++ >> kernel/locking/mutex-debug.c | 22 ++++++++++++++++++++++ >> 2 files changed, 35 insertions(+) >> >> diff --git a/include/linux/mutex.h b/include/linux/mutex.h >> index f7611c092db7..9bcf72cb941a 100644 >> --- a/include/linux/mutex.h >> +++ b/include/linux/mutex.h >> @@ -22,6 +22,8 @@ >> #include >> #include >> >> +struct device; >> + >> #ifdef CONFIG_DEBUG_LOCK_ALLOC >> # define __DEP_MAP_MUTEX_INITIALIZER(lockname) \ >> , .dep_map = { \ >> @@ -115,10 +117,21 @@ do { \ >> >> #ifdef CONFIG_DEBUG_MUTEXES >> >> +int devm_mutex_init(struct device *dev, struct mutex *lock); >> void mutex_destroy(struct mutex *lock); >> >> #else >> >> +static inline int devm_mutex_init(struct device *dev, struct mutex *lock) >> +{ >> + /* >> + * since mutex_destroy is nop actually there's no need to register it >> + * in devm subsystem. >> + */ >> + mutex_init(lock); >> + return 0; >> +} >> + >> static inline void mutex_destroy(struct mutex *lock) {} >> >> #endif >> diff --git a/kernel/locking/mutex-debug.c b/kernel/locking/mutex-debug.c >> index bc8abb8549d2..c9efab1a8026 100644 >> --- a/kernel/locking/mutex-debug.c >> +++ b/kernel/locking/mutex-debug.c >> @@ -19,6 +19,7 @@ >> #include >> #include >> #include >> +#include >> >> #include "mutex.h" >> >> @@ -104,3 +105,24 @@ void mutex_destroy(struct mutex *lock) >> } >> >> EXPORT_SYMBOL_GPL(mutex_destroy); >> + >> +static void devm_mutex_release(void *res) >> +{ >> + mutex_destroy(res); >> +} >> + >> +/** >> + * devm_mutex_init - Resource-managed mutex initialization >> + * @dev: Device which lifetime mutex is bound to >> + * @lock: Pointer to a mutex >> + * >> + * Initialize mutex which is automatically destroyed when the driver is detached. >> + * >> + * Returns: 0 on success or a negative error code on failure. >> + */ >> +int devm_mutex_init(struct device *dev, struct mutex *lock) >> +{ >> + mutex_init(lock); >> + return devm_add_action_or_reset(dev, devm_mutex_release, lock); >> +} >> +EXPORT_SYMBOL_GPL(devm_mutex_init); > Hi George, > > look at > https://lore.kernel.org/lkml/7013bf9e-2663-4613-ae61-61872e81355b@redhat.com/ > where Matthew and Hans explain that devm_mutex_init needs to be a macro > because of the static lockdep key. > > so this should be something like: > > static inline int __devm_mutex_init(struct device *dev, struct mutex *mutex, > const char *name, > struct lock_class_key *key) > { > __mutex_init(mutex, name, key); > return devm_add_action_or_reset(dev, devm_mutex_release, mutex); > } > > #define devm_mutex_init(dev, mutex) \ > do { \ > static struct lock_class_key __key; \ > \ > __devm_mutex_init(dev, (mutex), #mutex, &__key); \ > } while (0); > > > Marek Making devm_mutex_init() a function will make all the devm_mutex share the same lockdep key. Making it a macro will make each caller of devm_mutex_init() have a distinct lockdep key. It all depends on whether all the devm_mutexes have the same lock usage pattern or not and whether it is possible for one devm_mutex to be nested inside another. So either way can be fine depending on the mutex usage pattern. My suggestion is to use a function, if possible, unless it will cause a false positive lockdep splat as there is a limit on the maximum # of lockdep keys that can be used. Cheers, Longman From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from lists.ozlabs.org (lists.ozlabs.org [112.213.38.117]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 2A440C54798 for ; Thu, 7 Mar 2024 13:40:44 +0000 (UTC) Authentication-Results: lists.ozlabs.org; dkim=fail reason="signature verification failed" (1024-bit key; unprotected) header.d=redhat.com header.i=@redhat.com header.a=rsa-sha256 header.s=mimecast20190719 header.b=iyeW1MaJ; dkim=fail reason="signature verification failed" (1024-bit key) header.d=redhat.com header.i=@redhat.com header.a=rsa-sha256 header.s=mimecast20190719 header.b=iyeW1MaJ; dkim-atps=neutral Received: from boromir.ozlabs.org (localhost [IPv6:::1]) by lists.ozlabs.org (Postfix) with ESMTP id 4Tr9RZ5bgMz3cCx for ; Fri, 8 Mar 2024 00:40:42 +1100 (AEDT) Authentication-Results: lists.ozlabs.org; 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Thu, 07 Mar 2024 08:39:50 -0500 X-MC-Unique: PhGOQ0k9Pra5YEfCRg8aGQ-1 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.rdu2.redhat.com [10.11.54.7]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 1EA19101A523; Thu, 7 Mar 2024 13:39:49 +0000 (UTC) Received: from [10.22.17.9] (unknown [10.22.17.9]) by smtp.corp.redhat.com (Postfix) with ESMTP id 5BB371C0653F; Thu, 7 Mar 2024 13:39:47 +0000 (UTC) Message-ID: <3d95ab40-2df5-4988-87be-568a628a0561@redhat.com> Date: Thu, 7 Mar 2024 08:39:46 -0500 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v5 02/10] locking/mutex: introduce devm_mutex_init Content-Language: en-US To: =?UTF-8?Q?Marek_Beh=C3=BAn?= , George Stark References: <20240307024034.1548605-1-gnstark@salutedevices.com> <20240307024034.1548605-3-gnstark@salutedevices.com> <20240307095639.b6utkbzr36liuu3p@kandell> From: Waiman Long In-Reply-To: <20240307095639.b6utkbzr36liuu3p@kandell> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.7 X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: kabel@kernel.org, linuxppc-dev@lists.ozlabs.org, vadimp@nvidia.com, mazziesaccount@gmail.com, peterz@infradead.org, boqun.feng@gmail.com, lee@kernel.org, kernel@salutedevices.com, linux-kernel@vger.kernel.org, npiggin@gmail.com, hdegoede@redhat.com, andy.shevchenko@gmail.com, mingo@redhat.com, pavel@ucw.cz, nikitos.tr@gmail.com, will@kernel.org, linux-leds@vger.kernel.org Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On 3/7/24 04:56, Marek Behún wrote: > On Thu, Mar 07, 2024 at 05:40:26AM +0300, George Stark wrote: >> Using of devm API leads to a certain order of releasing resources. >> So all dependent resources which are not devm-wrapped should be deleted >> with respect to devm-release order. Mutex is one of such objects that >> often is bound to other resources and has no own devm wrapping. >> Since mutex_destroy() actually does nothing in non-debug builds >> frequently calling mutex_destroy() is just ignored which is safe for now >> but wrong formally and can lead to a problem if mutex_destroy() will be >> extended so introduce devm_mutex_init() >> >> Signed-off-by: George Stark >> Signed-off-by: Christophe Leroy >> --- >> Hello Christophe. Hope you don't mind I put you SoB tag because you helped alot >> to make this patch happen. >> >> include/linux/mutex.h | 13 +++++++++++++ >> kernel/locking/mutex-debug.c | 22 ++++++++++++++++++++++ >> 2 files changed, 35 insertions(+) >> >> diff --git a/include/linux/mutex.h b/include/linux/mutex.h >> index f7611c092db7..9bcf72cb941a 100644 >> --- a/include/linux/mutex.h >> +++ b/include/linux/mutex.h >> @@ -22,6 +22,8 @@ >> #include >> #include >> >> +struct device; >> + >> #ifdef CONFIG_DEBUG_LOCK_ALLOC >> # define __DEP_MAP_MUTEX_INITIALIZER(lockname) \ >> , .dep_map = { \ >> @@ -115,10 +117,21 @@ do { \ >> >> #ifdef CONFIG_DEBUG_MUTEXES >> >> +int devm_mutex_init(struct device *dev, struct mutex *lock); >> void mutex_destroy(struct mutex *lock); >> >> #else >> >> +static inline int devm_mutex_init(struct device *dev, struct mutex *lock) >> +{ >> + /* >> + * since mutex_destroy is nop actually there's no need to register it >> + * in devm subsystem. >> + */ >> + mutex_init(lock); >> + return 0; >> +} >> + >> static inline void mutex_destroy(struct mutex *lock) {} >> >> #endif >> diff --git a/kernel/locking/mutex-debug.c b/kernel/locking/mutex-debug.c >> index bc8abb8549d2..c9efab1a8026 100644 >> --- a/kernel/locking/mutex-debug.c >> +++ b/kernel/locking/mutex-debug.c >> @@ -19,6 +19,7 @@ >> #include >> #include >> #include >> +#include >> >> #include "mutex.h" >> >> @@ -104,3 +105,24 @@ void mutex_destroy(struct mutex *lock) >> } >> >> EXPORT_SYMBOL_GPL(mutex_destroy); >> + >> +static void devm_mutex_release(void *res) >> +{ >> + mutex_destroy(res); >> +} >> + >> +/** >> + * devm_mutex_init - Resource-managed mutex initialization >> + * @dev: Device which lifetime mutex is bound to >> + * @lock: Pointer to a mutex >> + * >> + * Initialize mutex which is automatically destroyed when the driver is detached. >> + * >> + * Returns: 0 on success or a negative error code on failure. >> + */ >> +int devm_mutex_init(struct device *dev, struct mutex *lock) >> +{ >> + mutex_init(lock); >> + return devm_add_action_or_reset(dev, devm_mutex_release, lock); >> +} >> +EXPORT_SYMBOL_GPL(devm_mutex_init); > Hi George, > > look at > https://lore.kernel.org/lkml/7013bf9e-2663-4613-ae61-61872e81355b@redhat.com/ > where Matthew and Hans explain that devm_mutex_init needs to be a macro > because of the static lockdep key. > > so this should be something like: > > static inline int __devm_mutex_init(struct device *dev, struct mutex *mutex, > const char *name, > struct lock_class_key *key) > { > __mutex_init(mutex, name, key); > return devm_add_action_or_reset(dev, devm_mutex_release, mutex); > } > > #define devm_mutex_init(dev, mutex) \ > do { \ > static struct lock_class_key __key; \ > \ > __devm_mutex_init(dev, (mutex), #mutex, &__key); \ > } while (0); > > > Marek Making devm_mutex_init() a function will make all the devm_mutex share the same lockdep key. Making it a macro will make each caller of devm_mutex_init() have a distinct lockdep key. It all depends on whether all the devm_mutexes have the same lock usage pattern or not and whether it is possible for one devm_mutex to be nested inside another. So either way can be fine depending on the mutex usage pattern. My suggestion is to use a function, if possible, unless it will cause a false positive lockdep splat as there is a limit on the maximum # of lockdep keys that can be used. Cheers, Longman