From nobody Thu Sep 19 19:36:36 2024 Received: from szxga04-in.huawei.com (szxga04-in.huawei.com [45.249.212.190]) (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 AF53E1A0BFA; Thu, 12 Sep 2024 12:51:11 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=45.249.212.190 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1726145474; cv=none; b=jF0D8ehRLpwQ/SjANLkW/d6s7J5N38YJtYZjC5K3RvyFpKrbveLRaGyDaAoAxv1v38VM42V0avhSTwug9J6auTIFOKcAw9AyKKOprytqigfW9XSIug21zDUz//eJakAVXrpCTV6XOWYvjK6iUJmjlPAOMBKXA57UkmjkGBsjsp4= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1726145474; c=relaxed/simple; bh=9yebMu2vCpQ+wu5Z5l9WP4ME7I74Jq6QtRrLnf1mRBg=; h=From:To:CC:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=hYJRCGmculWwR40KYkhZCyREq/t5PNkAYAqTFpk/o516P+MPsZMwWj7xHPdxBbYQZbniFw9ZHBtJcI2CRJOrtpUUwCYOBugyUCep77wkUvr4niqXeuLm+C3WJ2Ls0S40luyTuAHlkOXiY/4UhzX1iv8IQcfOW1AJydLtnBTJxPo= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=huawei.com; spf=pass smtp.mailfrom=huawei.com; arc=none smtp.client-ip=45.249.212.190 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=huawei.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=huawei.com Received: from mail.maildlp.com (unknown [172.19.88.214]) by szxga04-in.huawei.com (SkyGuard) with ESMTP id 4X4HP213Ymz20nrY; Thu, 12 Sep 2024 20:51:02 +0800 (CST) Received: from dggpemf200006.china.huawei.com (unknown [7.185.36.61]) by mail.maildlp.com (Postfix) with ESMTPS id 4EC651A016C; Thu, 12 Sep 2024 20:51:09 +0800 (CST) Received: from localhost.localdomain (10.90.30.45) by dggpemf200006.china.huawei.com (7.185.36.61) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1544.11; Thu, 12 Sep 2024 20:51:09 +0800 From: Yunsheng Lin To: , , CC: , , Yunsheng Lin , Alexander Lobakin , Jesper Dangaard Brouer , Ilias Apalodimas , Eric Dumazet , , Subject: [RFC 1/2] page_pool: fix timing for checking and disabling napi_local Date: Thu, 12 Sep 2024 20:45:12 +0800 Message-ID: <20240912124514.2329991-2-linyunsheng@huawei.com> X-Mailer: git-send-email 2.30.0 In-Reply-To: <20240912124514.2329991-1-linyunsheng@huawei.com> References: <20240912124514.2329991-1-linyunsheng@huawei.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-ClientProxiedBy: dggems702-chm.china.huawei.com (10.3.19.179) To dggpemf200006.china.huawei.com (7.185.36.61) Content-Type: text/plain; charset="utf-8" page_pool page may be freed from skb_defer_free_flush() to softirq context, it may cause concurrent access problem for pool->alloc cache due to the below time window, as below, both CPU0 and CPU1 may access the pool->alloc cache concurrently in page_pool_empty_alloc_cache_once() and page_pool_recycle_in_cache(): CPU 0 CPU1 page_pool_destroy() skb_defer_free_flush() . . . page_pool_put_unrefed_page() . . . allow_direct =3D page_pool_napi_local() . . page_pool_disable_direct_recycling() . . . page_pool_empty_alloc_cache_once() page_pool_recycle_in_cache() Use rcu mechanism to avoid the above concurrent access problem. Note, the above was found during code reviewing how to fix the problem in [1]. 1. https://lore.kernel.org/lkml/8067f204-1380-4d37-8ffd-007fc6f26738@kernel= .org/T/ Signed-off-by: Yunsheng Lin CC: Alexander Lobakin --- net/core/page_pool.c | 21 +++++++++++++++++++-- 1 file changed, 19 insertions(+), 2 deletions(-) diff --git a/net/core/page_pool.c b/net/core/page_pool.c index a813d30d2135..18645907cec2 100644 --- a/net/core/page_pool.c +++ b/net/core/page_pool.c @@ -818,6 +818,8 @@ static bool page_pool_napi_local(const struct page_pool= *pool) void page_pool_put_unrefed_netmem(struct page_pool *pool, netmem_ref netme= m, unsigned int dma_sync_size, bool allow_direct) { + rcu_read_lock(); + if (!allow_direct) allow_direct =3D page_pool_napi_local(pool); =20 @@ -828,6 +830,8 @@ void page_pool_put_unrefed_netmem(struct page_pool *poo= l, netmem_ref netmem, recycle_stat_inc(pool, ring_full); page_pool_return_page(pool, netmem); } + + rcu_read_unlock(); } EXPORT_SYMBOL(page_pool_put_unrefed_netmem); =20 @@ -861,6 +865,7 @@ void page_pool_put_page_bulk(struct page_pool *pool, vo= id **data, bool allow_direct; bool in_softirq; =20 + rcu_read_lock(); allow_direct =3D page_pool_napi_local(pool); =20 for (i =3D 0; i < count; i++) { @@ -876,8 +881,10 @@ void page_pool_put_page_bulk(struct page_pool *pool, v= oid **data, data[bulk_len++] =3D (__force void *)netmem; } =20 - if (!bulk_len) + if (!bulk_len) { + rcu_read_unlock(); return; + } =20 /* Bulk producer into ptr_ring page_pool cache */ in_softirq =3D page_pool_producer_lock(pool); @@ -892,14 +899,18 @@ void page_pool_put_page_bulk(struct page_pool *pool, = void **data, page_pool_producer_unlock(pool, in_softirq); =20 /* Hopefully all pages was return into ptr_ring */ - if (likely(i =3D=3D bulk_len)) + if (likely(i =3D=3D bulk_len)) { + rcu_read_unlock(); return; + } =20 /* ptr_ring cache full, free remaining pages outside producer lock * since put_page() with refcnt =3D=3D 1 can be an expensive operation */ for (; i < bulk_len; i++) page_pool_return_page(pool, (__force netmem_ref)data[i]); + + rcu_read_unlock(); } EXPORT_SYMBOL(page_pool_put_page_bulk); =20 @@ -1121,6 +1132,12 @@ void page_pool_destroy(struct page_pool *pool) return; =20 page_pool_disable_direct_recycling(pool); + + /* Wait for the freeing side see the disabling direct recycling setting + * to avoid the concurrent access to the pool->alloc cache. + */ + synchronize_rcu(); + page_pool_free_frag(pool); =20 if (!page_pool_release(pool)) --=20 2.33.0