From patchwork Thu Apr 7 08:59:45 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: =?utf-8?q?Christian_K=C3=B6nig?= X-Patchwork-Id: 12804855 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 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 smtp.lore.kernel.org (Postfix) with ESMTPS id 183D1C433EF for ; Thu, 7 Apr 2022 09:00:23 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 06ECE10E711; Thu, 7 Apr 2022 09:00:13 +0000 (UTC) Received: from mail-ej1-x62b.google.com (mail-ej1-x62b.google.com [IPv6:2a00:1450:4864:20::62b]) by gabe.freedesktop.org (Postfix) with ESMTPS id 4CEBA10E73A; Thu, 7 Apr 2022 09:00:08 +0000 (UTC) Received: by mail-ej1-x62b.google.com with SMTP id n6so9346161ejc.13; Thu, 07 Apr 2022 02:00:08 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=760zU6RiXAIuJGoNLn2/+bYMaUvztiATMp1AUPhE4GU=; b=q5sAcsteXjE5E6buvxHVwksfAOQLd+zFBEwX706pw8PsoRHvTCTP2AVKpJ63aR2Bh0 O9BnR7a6s1AF9ma4MvUfcaRdlRJo1BOtvutC3IbcBP+eziATr99bw7mfnJyxylFFVZJ6 CSh7ei2nLLq2Ldfm7bqqH3CxgAR7HiREMNLcBsk5o2Bfrn0f6IsgEICZRAt07gm3DiG2 9bVYqj4cFNXDAWECUmD8qiTJo9m/L1pABKwZI3+EbOcl8Sl9k9T5fCLlFwiUqGzBd+M2 Hw3rhCSbGcED/tXVf913lA/sM1vevBqnkOs0MvZ7//8h48HKVZzwYXz61QUlh8i7G1sy 0VDg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=760zU6RiXAIuJGoNLn2/+bYMaUvztiATMp1AUPhE4GU=; b=RmM2Km6f7wBUyIKeMi/wS8FRzB4L53kXjlKxhus/IcdeYoiFrPWyJ+rHivzihM1LL9 fRxCq6aPecSWWv6T/Gr8tUnIgVH8GQv1f1ldxxYpekpT/rl5y334x+W25EY2e9SeYWJV KC4lvnQfSEoMzM64odhv3tyukCmlWLrvRULlPq4yop7W/bnJxTO6ij+yj3UmudKhj8HE 1zitwjmiDJLqZjFG0VqYWDzRT+rbWT7KUz99TB+tyIhhpO1cYUH2zVo/BsgR2MiKjYlE TIxpGyNl6Pk0VWSD/LUj6UiNgWOJFhyPNMLHm3dsDYxdbVEY4SFE3pXHQsmjVPLkTqv9 aIdQ== X-Gm-Message-State: AOAM53352S0Q5QDiSaCoXuP0DywUUcLpi64i6sWVegnW5fMTWhoKiqXI ZAF9VTG/vQeW1ly6ekdOZZM= X-Google-Smtp-Source: ABdhPJzXzuQAt7xj669fvamaIe9WL9eeVhihRzkGBku2xHTH0wXLFGad+Fw66H/MLutFoSJz49X5qQ== X-Received: by 2002:a17:906:cccf:b0:6e7:5336:8bd7 with SMTP id ot15-20020a170906cccf00b006e753368bd7mr12482779ejb.583.1649322005423; Thu, 07 Apr 2022 02:00:05 -0700 (PDT) Received: from able.fritz.box (p57b0b9e1.dip0.t-ipconnect.de. [87.176.185.225]) by smtp.gmail.com with ESMTPSA id h26-20020a170906111a00b006e778bd4fc8sm5186563eja.38.2022.04.07.02.00.04 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 07 Apr 2022 02:00:04 -0700 (PDT) From: " =?utf-8?q?Christian_K=C3=B6nig?= " X-Google-Original-From: =?utf-8?q?Christian_K=C3=B6nig?= To: daniel.vetter@ffwll.ch, dri-devel@lists.freedesktop.org, linux-media@vger.kernel.org, linaro-mm-sig@lists.linaro.org, intel-gfx@lists.freedesktop.org Subject: [PATCH 14/15] dma-buf: drop seq count based update Date: Thu, 7 Apr 2022 10:59:45 +0200 Message-Id: <20220407085946.744568-15-christian.koenig@amd.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20220407085946.744568-1-christian.koenig@amd.com> References: <20220407085946.744568-1-christian.koenig@amd.com> MIME-Version: 1.0 X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: =?utf-8?q?Christian_K=C3=B6nig?= Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" This should be possible now since we don't have the distinction between exclusive and shared fences any more. The only possible pitfall is that a dma_fence would be reused during the RCU grace period, but even that could be handled with a single extra check. Signed-off-by: Christian König Reviewed-by: Daniel Vetter --- drivers/dma-buf/dma-resv.c | 33 ++++++++++++--------------------- drivers/dma-buf/st-dma-resv.c | 2 +- include/linux/dma-resv.h | 12 ------------ 3 files changed, 13 insertions(+), 34 deletions(-) diff --git a/drivers/dma-buf/dma-resv.c b/drivers/dma-buf/dma-resv.c index 5b64aa554c36..0cce6e4ec946 100644 --- a/drivers/dma-buf/dma-resv.c +++ b/drivers/dma-buf/dma-resv.c @@ -133,7 +133,6 @@ static void dma_resv_list_free(struct dma_resv_list *list) void dma_resv_init(struct dma_resv *obj) { ww_mutex_init(&obj->lock, &reservation_ww_class); - seqcount_ww_mutex_init(&obj->seq, &obj->lock); RCU_INIT_POINTER(obj->fences, NULL); } @@ -292,28 +291,24 @@ void dma_resv_add_fence(struct dma_resv *obj, struct dma_fence *fence, fobj = dma_resv_fences_list(obj); count = fobj->num_fences; - write_seqcount_begin(&obj->seq); - for (i = 0; i < count; ++i) { enum dma_resv_usage old_usage; dma_resv_list_entry(fobj, i, obj, &old, &old_usage); if ((old->context == fence->context && old_usage >= usage) || - dma_fence_is_signaled(old)) - goto replace; + dma_fence_is_signaled(old)) { + dma_resv_list_set(fobj, i, fence, usage); + dma_fence_put(old); + return; + } } BUG_ON(fobj->num_fences >= fobj->max_fences); - old = NULL; count++; -replace: dma_resv_list_set(fobj, i, fence, usage); /* pointer update must be visible before we extend the num_fences */ smp_store_mb(fobj->num_fences, count); - - write_seqcount_end(&obj->seq); - dma_fence_put(old); } EXPORT_SYMBOL(dma_resv_add_fence); @@ -341,7 +336,6 @@ void dma_resv_replace_fences(struct dma_resv *obj, uint64_t context, dma_resv_assert_held(obj); list = dma_resv_fences_list(obj); - write_seqcount_begin(&obj->seq); for (i = 0; list && i < list->num_fences; ++i) { struct dma_fence *old; @@ -352,14 +346,12 @@ void dma_resv_replace_fences(struct dma_resv *obj, uint64_t context, dma_resv_list_set(list, i, replacement, usage); dma_fence_put(old); } - write_seqcount_end(&obj->seq); } EXPORT_SYMBOL(dma_resv_replace_fences); /* 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 = 0; cursor->num_fences = 0; cursor->fences = dma_resv_fences_list(cursor->obj); @@ -388,8 +380,10 @@ static void dma_resv_iter_walk_unlocked(struct dma_resv_iter *cursor) cursor->obj, &cursor->fence, &cursor->fence_usage); cursor->fence = dma_fence_get_rcu(cursor->fence); - if (!cursor->fence) - break; + if (!cursor->fence) { + dma_resv_iter_restart_unlocked(cursor); + continue; + } if (!dma_fence_is_signaled(cursor->fence) && cursor->usage >= cursor->fence_usage) @@ -415,7 +409,7 @@ struct dma_fence *dma_resv_iter_first_unlocked(struct dma_resv_iter *cursor) do { dma_resv_iter_restart_unlocked(cursor); dma_resv_iter_walk_unlocked(cursor); - } while (read_seqcount_retry(&cursor->obj->seq, cursor->seq)); + } while (dma_resv_fences_list(cursor->obj) != cursor->fences); rcu_read_unlock(); return cursor->fence; @@ -438,13 +432,13 @@ struct dma_fence *dma_resv_iter_next_unlocked(struct dma_resv_iter *cursor) rcu_read_lock(); cursor->is_restarted = false; - restart = read_seqcount_retry(&cursor->obj->seq, cursor->seq); + restart = dma_resv_fences_list(cursor->obj) != cursor->fences; 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)); + } while (dma_resv_fences_list(cursor->obj) != cursor->fences); rcu_read_unlock(); return cursor->fence; @@ -540,10 +534,7 @@ int dma_resv_copy_fences(struct dma_resv *dst, struct dma_resv *src) } dma_resv_iter_end(&cursor); - write_seqcount_begin(&dst->seq); list = rcu_replace_pointer(dst->fences, list, dma_resv_held(dst)); - write_seqcount_end(&dst->seq); - dma_resv_list_free(list); return 0; } diff --git a/drivers/dma-buf/st-dma-resv.c b/drivers/dma-buf/st-dma-resv.c index 8ace9e84c845..813779e3c9be 100644 --- a/drivers/dma-buf/st-dma-resv.c +++ b/drivers/dma-buf/st-dma-resv.c @@ -217,7 +217,7 @@ static int test_for_each_unlocked(void *arg) if (r == -ENOENT) { r = -EINVAL; /* That should trigger an restart */ - cursor.seq--; + cursor.fences = (void*)~0; } else if (r == -EINVAL) { r = 0; } diff --git a/include/linux/dma-resv.h b/include/linux/dma-resv.h index 1db759eacc98..c8ccbc94d5d2 100644 --- a/include/linux/dma-resv.h +++ b/include/linux/dma-resv.h @@ -155,15 +155,6 @@ struct dma_resv { */ struct ww_mutex lock; - /** - * @seq: - * - * Sequence count for managing RCU read-side synchronization, allows - * read-only access to @fences while ensuring we take a consistent - * snapshot. - */ - seqcount_ww_mutex_t seq; - /** * @fences: * @@ -202,9 +193,6 @@ struct dma_resv_iter { /** @fence_usage: the usage of the current fence */ enum dma_resv_usage fence_usage; - /** @seq: sequence number to check for modifications */ - unsigned int seq; - /** @index: index into the shared fences */ unsigned int index;