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 X-Spam-Level: X-Spam-Status: No, score=-14.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,HK_RANDOM_FROM,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id BDCEFC433F5 for ; Wed, 22 Sep 2021 14:37:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9B644611C9 for ; Wed, 22 Sep 2021 14:37:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236059AbhIVOi6 (ORCPT ); Wed, 22 Sep 2021 10:38:58 -0400 Received: from mga09.intel.com ([134.134.136.24]:23927 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232720AbhIVOi6 (ORCPT ); Wed, 22 Sep 2021 10:38:58 -0400 X-IronPort-AV: E=McAfee;i="6200,9189,10114"; a="223640694" X-IronPort-AV: E=Sophos;i="5.85,314,1624345200"; d="scan'208";a="223640694" Received: from fmsmga005.fm.intel.com ([10.253.24.32]) by orsmga102.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 22 Sep 2021 07:36:33 -0700 X-IronPort-AV: E=Sophos;i="5.85,314,1624345200"; d="scan'208";a="704043056" Received: from bbrowne-mobl.ger.corp.intel.com (HELO [10.213.200.151]) ([10.213.200.151]) by fmsmga005-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 22 Sep 2021 07:36:31 -0700 Subject: Re: [PATCH 01/26] dma-buf: add dma_resv_for_each_fence_unlocked v4 To: =?UTF-8?Q?Christian_K=c3=b6nig?= , linaro-mm-sig@lists.linaro.org, dri-devel@lists.freedesktop.org, linux-media@vger.kernel.org, intel-gfx@lists.freedesktop.org Cc: daniel@ffwll.ch References: <20210922091044.2612-1-christian.koenig@amd.com> <20210922091044.2612-2-christian.koenig@amd.com> From: Tvrtko Ursulin Organization: Intel Corporation UK Plc Message-ID: <093432d2-de8e-9684-03aa-7cb4842ea755@linux.intel.com> Date: Wed, 22 Sep 2021 15:36:29 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.13.0 MIME-Version: 1.0 In-Reply-To: <20210922091044.2612-2-christian.koenig@amd.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-media@vger.kernel.org On 22/09/2021 10:10, Christian König wrote: > Abstract the complexity of iterating over all the fences > in a dma_resv object. > > The new loop handles the whole RCU and retry dance and > returns only fences where we can be sure we grabbed the > right one. > > v2: fix accessing the shared fences while they might be freed, > improve kerneldoc, rename _cursor to _iter, add > dma_resv_iter_is_exclusive, add dma_resv_iter_begin/end > > v3: restructor the code, move rcu_read_lock()/unlock() into the > iterator, add dma_resv_iter_is_restarted() > > v4: fix NULL deref when no explicit fence exists, drop superflous > rcu_read_lock()/unlock() calls. > > Signed-off-by: Christian König > --- > drivers/dma-buf/dma-resv.c | 95 ++++++++++++++++++++++++++++++++++++++ > include/linux/dma-resv.h | 95 ++++++++++++++++++++++++++++++++++++++ > 2 files changed, 190 insertions(+) > > diff --git a/drivers/dma-buf/dma-resv.c b/drivers/dma-buf/dma-resv.c > index 84fbe60629e3..7768140ab36d 100644 > --- a/drivers/dma-buf/dma-resv.c > +++ b/drivers/dma-buf/dma-resv.c > @@ -323,6 +323,101 @@ void dma_resv_add_excl_fence(struct dma_resv *obj, struct dma_fence *fence) > } > EXPORT_SYMBOL(dma_resv_add_excl_fence); > > +/** > + * dma_resv_iter_restart_unlocked - restart the unlocked iterator > + * @cursor: The dma_resv_iter object to restart > + * > + * Restart the unlocked iteration by initializing the cursor object. > + */ > +static void dma_resv_iter_restart_unlocked(struct dma_resv_iter *cursor) > +{ > + cursor->seq = read_seqcount_begin(&cursor->obj->seq); > + cursor->index = -1; > + if (cursor->all_fences) > + cursor->fences = dma_resv_shared_list(cursor->obj); > + else > + cursor->fences = NULL; > + cursor->is_restarted = true; > +} > + > +/** > + * dma_resv_iter_walk_unlocked - walk over fences in a dma_resv obj > + * @cursor: cursor to record the current position > + * > + * Return all the fences in the dma_resv object which are not yet signaled. > + * The returned fence has an extra local reference so will stay alive. > + * If a concurrent modify is detected the whole iterration is started over again. iteration > + */ > +static void dma_resv_iter_walk_unlocked(struct dma_resv_iter *cursor) > +{ > + struct dma_resv *obj = cursor->obj; > + > + do { > + /* Drop the reference from the previous round */ > + dma_fence_put(cursor->fence); > + > + if (cursor->index++ == -1) { > + cursor->fence = dma_resv_excl_fence(obj); > + > + } else if (!cursor->fences || > + cursor->index >= cursor->fences->shared_count) { > + cursor->fence = NULL; > + > + } else { > + struct dma_resv_list *fences = cursor->fences; > + unsigned int idx = cursor->index; > + > + cursor->fence = rcu_dereference(fences->shared[idx]); > + } > + if (cursor->fence) > + cursor->fence = dma_fence_get_rcu(cursor->fence); > + } while (cursor->fence && dma_fence_is_signaled(cursor->fence)); > +} > + > +/** > + * dma_resv_iter_first_unlocked - first fence in an unlocked dma_resv obj. > + * @cursor: the cursor with the current position > + * > + * Returns the first fence from an unlocked dma_resv obj. > + */ > +struct dma_fence *dma_resv_iter_first_unlocked(struct dma_resv_iter *cursor) > +{ > + rcu_read_lock(); > + do { > + dma_resv_iter_restart_unlocked(cursor); > + dma_resv_iter_walk_unlocked(cursor); > + } while (read_seqcount_retry(&cursor->obj->seq, cursor->seq)); > + rcu_read_unlock(); > + > + return cursor->fence; > +} > +EXPORT_SYMBOL(dma_resv_iter_first_unlocked); Why is this one split from dma_resv_iter_begin and even exported? I couldn't find any users in the series. > + > +/** > + * dma_resv_iter_next_unlocked - next fence in an unlocked dma_resv obj. > + * @cursor: the cursor with the current position > + * > + * Returns the next fence from an unlocked dma_resv obj. > + */ > +struct dma_fence *dma_resv_iter_next_unlocked(struct dma_resv_iter *cursor) > +{ > + bool restart; > + > + rcu_read_lock(); > + cursor->is_restarted = false; > + restart = read_seqcount_retry(&cursor->obj->seq, cursor->seq); > + do { > + if (restart) > + dma_resv_iter_restart_unlocked(cursor); > + dma_resv_iter_walk_unlocked(cursor); > + restart = true; > + } while (read_seqcount_retry(&cursor->obj->seq, cursor->seq)); > + rcu_read_unlock(); > + > + return cursor->fence; > +} > +EXPORT_SYMBOL(dma_resv_iter_next_unlocked); Couldn't dma_resv_iter_first_unlocked and dma_resv_iter_next_unlocked share the same implementation? Especially if you are able to replace cursor->is_restarted with cursor->index == -1. > + > /** > * dma_resv_copy_fences - Copy all fences from src to dst. > * @dst: the destination reservation object > diff --git a/include/linux/dma-resv.h b/include/linux/dma-resv.h > index 9100dd3dc21f..baf77a542392 100644 > --- a/include/linux/dma-resv.h > +++ b/include/linux/dma-resv.h > @@ -149,6 +149,101 @@ struct dma_resv { > struct dma_resv_list __rcu *fence; > }; > > +/** > + * struct dma_resv_iter - current position into the dma_resv fences > + * > + * Don't touch this directly in the driver, use the accessor function instead. > + */ > +struct dma_resv_iter { > + /** @obj: The dma_resv object we iterate over */ > + struct dma_resv *obj; > + > + /** @all_fences: If all fences should be returned */ > + bool all_fences; > + > + /** @fence: the currently handled fence */ > + struct dma_fence *fence; > + > + /** @seq: sequence number to check for modifications */ > + unsigned int seq; > + > + /** @index: index into the shared fences */ > + unsigned int index; > + > + /** @fences: the shared fences */ > + struct dma_resv_list *fences; > + > + /** @is_restarted: true if this is the first returned fence */ > + bool is_restarted; > +}; > + > +struct dma_fence *dma_resv_iter_first_unlocked(struct dma_resv_iter *cursor); > +struct dma_fence *dma_resv_iter_next_unlocked(struct dma_resv_iter *cursor); > + > +/** > + * dma_resv_iter_begin - initialize a dma_resv_iter object > + * @cursor: The dma_resv_iter object to initialize > + * @obj: The dma_resv object which we want to iterator over iterate > + * @all_fences: If all fences should be returned or just the exclusive one > + */ > +static inline void dma_resv_iter_begin(struct dma_resv_iter *cursor, > + struct dma_resv *obj, > + bool all_fences) > +{ > + cursor->obj = obj; > + cursor->all_fences = all_fences; > + cursor->fence = NULL; > +} > + > +/** > + * dma_resv_iter_end - cleanup a dma_resv_iter object > + * @cursor: the dma_resv_iter object which should be cleaned up > + * > + * Make sure that the reference to the fence in the cursor is properly > + * dropped. > + */ > +static inline void dma_resv_iter_end(struct dma_resv_iter *cursor) > +{ > + dma_fence_put(cursor->fence); > +} > + > +/** > + * dma_resv_iter_is_exclusive - test if the current fence is the exclusive one > + * @cursor: the cursor of the current position > + * > + * Returns true if the currently returned fence is the exclusive one. > + */ > +static inline bool dma_resv_iter_is_exclusive(struct dma_resv_iter *cursor) > +{ > + return cursor->index == -1; > +} > + > +/** > + * dma_resv_iter_is_restarted - test if this is the first fence after a restart > + * @cursor: the cursor with the current position > + * > + * Return true if this is the first fence in an interation after a restart. iteration > + */ > +static inline bool dma_resv_iter_is_restarted(struct dma_resv_iter *cursor) > +{ > + return cursor->is_restarted; > +} > + > +/** > + * dma_resv_for_each_fence_unlocked - unlocked fence iterator > + * @cursor: a struct dma_resv_iter pointer > + * @fence: the current fence > + * > + * Iterate over the fences in a struct dma_resv object without holding the > + * &dma_resv.lock and using RCU instead. The cursor needs to be initialized > + * with dma_resv_iter_begin() and cleaned up with dma_resv_iter_end(). Inside > + * the iterator a reference to the dma_fence is hold and the RCU lock dropped. held > + * When the dma_resv is modified the iteration starts over again. > + */ > +#define dma_resv_for_each_fence_unlocked(cursor, fence) \ > + for (fence = dma_resv_iter_first_unlocked(cursor); \ > + fence; fence = dma_resv_iter_next_unlocked(cursor)) > + > #define dma_resv_held(obj) lockdep_is_held(&(obj)->lock.base) > #define dma_resv_assert_held(obj) lockdep_assert_held(&(obj)->lock.base) > > Regards, Tvrtko 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 X-Spam-Level: X-Spam-Status: No, score=-14.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,HK_RANDOM_FROM,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8410AC433F5 for ; Wed, 22 Sep 2021 14:37:47 +0000 (UTC) Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 26B0460F26 for ; Wed, 22 Sep 2021 14:37:47 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 26B0460F26 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.intel.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=lists.freedesktop.org Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id D3C6C6EBFD; Wed, 22 Sep 2021 14:37:42 +0000 (UTC) Received: from mga05.intel.com (mga05.intel.com [192.55.52.43]) by gabe.freedesktop.org (Postfix) with ESMTPS id DEBDF6E831; Wed, 22 Sep 2021 14:37:40 +0000 (UTC) X-IronPort-AV: E=McAfee;i="6200,9189,10114"; a="309161512" X-IronPort-AV: E=Sophos;i="5.85,314,1624345200"; d="scan'208";a="309161512" Received: from fmsmga005.fm.intel.com ([10.253.24.32]) by fmsmga105.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 22 Sep 2021 07:36:33 -0700 X-IronPort-AV: E=Sophos;i="5.85,314,1624345200"; d="scan'208";a="704043056" Received: from bbrowne-mobl.ger.corp.intel.com (HELO [10.213.200.151]) ([10.213.200.151]) by fmsmga005-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 22 Sep 2021 07:36:31 -0700 To: =?UTF-8?Q?Christian_K=c3=b6nig?= , linaro-mm-sig@lists.linaro.org, dri-devel@lists.freedesktop.org, linux-media@vger.kernel.org, intel-gfx@lists.freedesktop.org Cc: daniel@ffwll.ch References: <20210922091044.2612-1-christian.koenig@amd.com> <20210922091044.2612-2-christian.koenig@amd.com> From: Tvrtko Ursulin Organization: Intel Corporation UK Plc Message-ID: <093432d2-de8e-9684-03aa-7cb4842ea755@linux.intel.com> Date: Wed, 22 Sep 2021 15:36:29 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.13.0 MIME-Version: 1.0 In-Reply-To: <20210922091044.2612-2-christian.koenig@amd.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit Subject: Re: [Intel-gfx] [PATCH 01/26] dma-buf: add dma_resv_for_each_fence_unlocked v4 X-BeenThere: intel-gfx@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Intel graphics driver community testing & development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: intel-gfx-bounces@lists.freedesktop.org Sender: "Intel-gfx" On 22/09/2021 10:10, Christian König wrote: > Abstract the complexity of iterating over all the fences > in a dma_resv object. > > The new loop handles the whole RCU and retry dance and > returns only fences where we can be sure we grabbed the > right one. > > v2: fix accessing the shared fences while they might be freed, > improve kerneldoc, rename _cursor to _iter, add > dma_resv_iter_is_exclusive, add dma_resv_iter_begin/end > > v3: restructor the code, move rcu_read_lock()/unlock() into the > iterator, add dma_resv_iter_is_restarted() > > v4: fix NULL deref when no explicit fence exists, drop superflous > rcu_read_lock()/unlock() calls. > > Signed-off-by: Christian König > --- > drivers/dma-buf/dma-resv.c | 95 ++++++++++++++++++++++++++++++++++++++ > include/linux/dma-resv.h | 95 ++++++++++++++++++++++++++++++++++++++ > 2 files changed, 190 insertions(+) > > diff --git a/drivers/dma-buf/dma-resv.c b/drivers/dma-buf/dma-resv.c > index 84fbe60629e3..7768140ab36d 100644 > --- a/drivers/dma-buf/dma-resv.c > +++ b/drivers/dma-buf/dma-resv.c > @@ -323,6 +323,101 @@ void dma_resv_add_excl_fence(struct dma_resv *obj, struct dma_fence *fence) > } > EXPORT_SYMBOL(dma_resv_add_excl_fence); > > +/** > + * dma_resv_iter_restart_unlocked - restart the unlocked iterator > + * @cursor: The dma_resv_iter object to restart > + * > + * Restart the unlocked iteration by initializing the cursor object. > + */ > +static void dma_resv_iter_restart_unlocked(struct dma_resv_iter *cursor) > +{ > + cursor->seq = read_seqcount_begin(&cursor->obj->seq); > + cursor->index = -1; > + if (cursor->all_fences) > + cursor->fences = dma_resv_shared_list(cursor->obj); > + else > + cursor->fences = NULL; > + cursor->is_restarted = true; > +} > + > +/** > + * dma_resv_iter_walk_unlocked - walk over fences in a dma_resv obj > + * @cursor: cursor to record the current position > + * > + * Return all the fences in the dma_resv object which are not yet signaled. > + * The returned fence has an extra local reference so will stay alive. > + * If a concurrent modify is detected the whole iterration is started over again. iteration > + */ > +static void dma_resv_iter_walk_unlocked(struct dma_resv_iter *cursor) > +{ > + struct dma_resv *obj = cursor->obj; > + > + do { > + /* Drop the reference from the previous round */ > + dma_fence_put(cursor->fence); > + > + if (cursor->index++ == -1) { > + cursor->fence = dma_resv_excl_fence(obj); > + > + } else if (!cursor->fences || > + cursor->index >= cursor->fences->shared_count) { > + cursor->fence = NULL; > + > + } else { > + struct dma_resv_list *fences = cursor->fences; > + unsigned int idx = cursor->index; > + > + cursor->fence = rcu_dereference(fences->shared[idx]); > + } > + if (cursor->fence) > + cursor->fence = dma_fence_get_rcu(cursor->fence); > + } while (cursor->fence && dma_fence_is_signaled(cursor->fence)); > +} > + > +/** > + * dma_resv_iter_first_unlocked - first fence in an unlocked dma_resv obj. > + * @cursor: the cursor with the current position > + * > + * Returns the first fence from an unlocked dma_resv obj. > + */ > +struct dma_fence *dma_resv_iter_first_unlocked(struct dma_resv_iter *cursor) > +{ > + rcu_read_lock(); > + do { > + dma_resv_iter_restart_unlocked(cursor); > + dma_resv_iter_walk_unlocked(cursor); > + } while (read_seqcount_retry(&cursor->obj->seq, cursor->seq)); > + rcu_read_unlock(); > + > + return cursor->fence; > +} > +EXPORT_SYMBOL(dma_resv_iter_first_unlocked); Why is this one split from dma_resv_iter_begin and even exported? I couldn't find any users in the series. > + > +/** > + * dma_resv_iter_next_unlocked - next fence in an unlocked dma_resv obj. > + * @cursor: the cursor with the current position > + * > + * Returns the next fence from an unlocked dma_resv obj. > + */ > +struct dma_fence *dma_resv_iter_next_unlocked(struct dma_resv_iter *cursor) > +{ > + bool restart; > + > + rcu_read_lock(); > + cursor->is_restarted = false; > + restart = read_seqcount_retry(&cursor->obj->seq, cursor->seq); > + do { > + if (restart) > + dma_resv_iter_restart_unlocked(cursor); > + dma_resv_iter_walk_unlocked(cursor); > + restart = true; > + } while (read_seqcount_retry(&cursor->obj->seq, cursor->seq)); > + rcu_read_unlock(); > + > + return cursor->fence; > +} > +EXPORT_SYMBOL(dma_resv_iter_next_unlocked); Couldn't dma_resv_iter_first_unlocked and dma_resv_iter_next_unlocked share the same implementation? Especially if you are able to replace cursor->is_restarted with cursor->index == -1. > + > /** > * dma_resv_copy_fences - Copy all fences from src to dst. > * @dst: the destination reservation object > diff --git a/include/linux/dma-resv.h b/include/linux/dma-resv.h > index 9100dd3dc21f..baf77a542392 100644 > --- a/include/linux/dma-resv.h > +++ b/include/linux/dma-resv.h > @@ -149,6 +149,101 @@ struct dma_resv { > struct dma_resv_list __rcu *fence; > }; > > +/** > + * struct dma_resv_iter - current position into the dma_resv fences > + * > + * Don't touch this directly in the driver, use the accessor function instead. > + */ > +struct dma_resv_iter { > + /** @obj: The dma_resv object we iterate over */ > + struct dma_resv *obj; > + > + /** @all_fences: If all fences should be returned */ > + bool all_fences; > + > + /** @fence: the currently handled fence */ > + struct dma_fence *fence; > + > + /** @seq: sequence number to check for modifications */ > + unsigned int seq; > + > + /** @index: index into the shared fences */ > + unsigned int index; > + > + /** @fences: the shared fences */ > + struct dma_resv_list *fences; > + > + /** @is_restarted: true if this is the first returned fence */ > + bool is_restarted; > +}; > + > +struct dma_fence *dma_resv_iter_first_unlocked(struct dma_resv_iter *cursor); > +struct dma_fence *dma_resv_iter_next_unlocked(struct dma_resv_iter *cursor); > + > +/** > + * dma_resv_iter_begin - initialize a dma_resv_iter object > + * @cursor: The dma_resv_iter object to initialize > + * @obj: The dma_resv object which we want to iterator over iterate > + * @all_fences: If all fences should be returned or just the exclusive one > + */ > +static inline void dma_resv_iter_begin(struct dma_resv_iter *cursor, > + struct dma_resv *obj, > + bool all_fences) > +{ > + cursor->obj = obj; > + cursor->all_fences = all_fences; > + cursor->fence = NULL; > +} > + > +/** > + * dma_resv_iter_end - cleanup a dma_resv_iter object > + * @cursor: the dma_resv_iter object which should be cleaned up > + * > + * Make sure that the reference to the fence in the cursor is properly > + * dropped. > + */ > +static inline void dma_resv_iter_end(struct dma_resv_iter *cursor) > +{ > + dma_fence_put(cursor->fence); > +} > + > +/** > + * dma_resv_iter_is_exclusive - test if the current fence is the exclusive one > + * @cursor: the cursor of the current position > + * > + * Returns true if the currently returned fence is the exclusive one. > + */ > +static inline bool dma_resv_iter_is_exclusive(struct dma_resv_iter *cursor) > +{ > + return cursor->index == -1; > +} > + > +/** > + * dma_resv_iter_is_restarted - test if this is the first fence after a restart > + * @cursor: the cursor with the current position > + * > + * Return true if this is the first fence in an interation after a restart. iteration > + */ > +static inline bool dma_resv_iter_is_restarted(struct dma_resv_iter *cursor) > +{ > + return cursor->is_restarted; > +} > + > +/** > + * dma_resv_for_each_fence_unlocked - unlocked fence iterator > + * @cursor: a struct dma_resv_iter pointer > + * @fence: the current fence > + * > + * Iterate over the fences in a struct dma_resv object without holding the > + * &dma_resv.lock and using RCU instead. The cursor needs to be initialized > + * with dma_resv_iter_begin() and cleaned up with dma_resv_iter_end(). Inside > + * the iterator a reference to the dma_fence is hold and the RCU lock dropped. held > + * When the dma_resv is modified the iteration starts over again. > + */ > +#define dma_resv_for_each_fence_unlocked(cursor, fence) \ > + for (fence = dma_resv_iter_first_unlocked(cursor); \ > + fence; fence = dma_resv_iter_next_unlocked(cursor)) > + > #define dma_resv_held(obj) lockdep_is_held(&(obj)->lock.base) > #define dma_resv_assert_held(obj) lockdep_assert_held(&(obj)->lock.base) > > Regards, Tvrtko