From patchwork Fri May 3 18:25:08 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Sebastian Andrzej Siewior X-Patchwork-Id: 13653315 X-Patchwork-Delegate: kuba@kernel.org Received: from galois.linutronix.de (Galois.linutronix.de [193.142.43.55]) (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 0AD1E158219; Fri, 3 May 2024 18:30:08 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=193.142.43.55 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1714761011; cv=none; b=Qmnp1pZmH2YjS1G8u5107LY0th8JUAn15+P/9AM5md2eiIYPiGGDLTl+v4qmi5tWRIany33JkZTESyPHxGquwzPPGWCjqHE+A0e0PHFBQsLjATSP+VFpwVidVmXuoWmzKbmoB9fUkvVrKDfCWP6TuCrRGS+V7Wb7RIPVXpoe/RY= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1714761011; c=relaxed/simple; bh=6F+WmYxkkmptqKxlRwOLSf3Q3FyJx8XzwEyn4NvBr2U=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=vEC+6pSK/QwD9RQ6Ilq6GInYa4yun8sLV2tMc4vY/l1cwGdJN+N2kg5klNCW2oTiXXog+RghyJcddFgqR391tuRMesax4OQVCJQlaJvNOUfuBeyj2wfqTuhGmVKjUKgGdIW+0D3XWQqckHabyi2lAwe83Mb+bJ5Tg4Jcj9+qqCg= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linutronix.de; spf=pass smtp.mailfrom=linutronix.de; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=PduJYgXL; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=sAykS50v; arc=none smtp.client-ip=193.142.43.55 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linutronix.de Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linutronix.de Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="PduJYgXL"; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="sAykS50v" From: Sebastian Andrzej Siewior DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1714761007; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=biQ9vBP/OT8ssEpkU2fNQ/MUE/WSCld+B29qWDwe4EE=; b=PduJYgXLFW8KhQlib6ILzf43dkAgdVfolaXAQDMwftvbClGp4aUIT2v8HSS/n+jWqs8pqz c/EyxeHX5W5pIi5Y0RNx5tU/5slQOz0XXf/JGWv0Wj+AYZT9zqXvIyoQIeAmD7ha4ySlrP 5zJQFWSK7ILNcfJQoTr+4Lur66NrlxH1Zj64llpTeh4VFvTBbILe+HNzm6bbK5NzlxU5Dn yLInyjnw6Sf+t7w0e/zuisde7Zmt+oSpSfwZillpu+ROIykkKQST9l9suETjcgCr0mF49E R7oHBpSHX3IEJJQ2cCTUPzjGxH+pIzeJbxVKPgTUS6LuZleId1sx89djz9iR4g== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1714761007; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=biQ9vBP/OT8ssEpkU2fNQ/MUE/WSCld+B29qWDwe4EE=; b=sAykS50vReWHQQAXvBFRKvJI0gooB3GHpl9sJL6vNypzWmmWJBMb5yf2eaOSDLqCajrgDT uzaBbKS/jdaKEHBw== To: linux-kernel@vger.kernel.org, netdev@vger.kernel.org Cc: "David S. Miller" , Boqun Feng , Daniel Borkmann , Eric Dumazet , Frederic Weisbecker , Ingo Molnar , Jakub Kicinski , Paolo Abeni , Peter Zijlstra , Thomas Gleixner , Waiman Long , Will Deacon , Sebastian Andrzej Siewior Subject: [PATCH net-next 04/15] net: Use nested-BH locking for napi_alloc_cache. Date: Fri, 3 May 2024 20:25:08 +0200 Message-ID: <20240503182957.1042122-5-bigeasy@linutronix.de> In-Reply-To: <20240503182957.1042122-1-bigeasy@linutronix.de> References: <20240503182957.1042122-1-bigeasy@linutronix.de> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Patchwork-Delegate: kuba@kernel.org napi_alloc_cache is a per-CPU variable and relies on disabled BH for its locking. Without per-CPU locking in local_bh_disable() on PREEMPT_RT this data structure requires explicit locking. Add a local_lock_t to the data structure and use local_lock_nested_bh() for locking. This change adds only lockdep coverage and does not alter the functional behaviour for !PREEMPT_RT. Signed-off-by: Sebastian Andrzej Siewior --- net/core/skbuff.c | 17 ++++++++++++++--- 1 file changed, 14 insertions(+), 3 deletions(-) diff --git a/net/core/skbuff.c b/net/core/skbuff.c index c4479d5721a2a..c8b40e6237057 100644 --- a/net/core/skbuff.c +++ b/net/core/skbuff.c @@ -277,6 +277,7 @@ static void *page_frag_alloc_1k(struct page_frag_1k *nc, gfp_t gfp_mask) #endif struct napi_alloc_cache { + local_lock_t bh_lock; struct page_frag_cache page; struct page_frag_1k page_small; unsigned int skb_count; @@ -284,7 +285,9 @@ struct napi_alloc_cache { }; static DEFINE_PER_CPU(struct page_frag_cache, netdev_alloc_cache); -static DEFINE_PER_CPU(struct napi_alloc_cache, napi_alloc_cache); +static DEFINE_PER_CPU(struct napi_alloc_cache, napi_alloc_cache) = { + .bh_lock = INIT_LOCAL_LOCK(bh_lock), +}; /* Double check that napi_get_frags() allocates skbs with * skb->head being backed by slab, not a page fragment. @@ -308,6 +311,7 @@ void *__napi_alloc_frag_align(unsigned int fragsz, unsigned int align_mask) struct napi_alloc_cache *nc = this_cpu_ptr(&napi_alloc_cache); fragsz = SKB_DATA_ALIGN(fragsz); + guard(local_lock_nested_bh)(&napi_alloc_cache.bh_lock); return __page_frag_alloc_align(&nc->page, fragsz, GFP_ATOMIC, align_mask); @@ -338,6 +342,7 @@ static struct sk_buff *napi_skb_cache_get(void) struct napi_alloc_cache *nc = this_cpu_ptr(&napi_alloc_cache); struct sk_buff *skb; + guard(local_lock_nested_bh)(&napi_alloc_cache.bh_lock); if (unlikely(!nc->skb_count)) { nc->skb_count = kmem_cache_alloc_bulk(net_hotdata.skbuff_cache, GFP_ATOMIC, @@ -740,9 +745,13 @@ struct sk_buff *__netdev_alloc_skb(struct net_device *dev, unsigned int len, pfmemalloc = nc->pfmemalloc; } else { local_bh_disable(); + local_lock_nested_bh(&napi_alloc_cache.bh_lock); + nc = this_cpu_ptr(&napi_alloc_cache.page); data = page_frag_alloc(nc, len, gfp_mask); pfmemalloc = nc->pfmemalloc; + + local_unlock_nested_bh(&napi_alloc_cache.bh_lock); local_bh_enable(); } @@ -806,11 +815,11 @@ struct sk_buff *napi_alloc_skb(struct napi_struct *napi, unsigned int len) goto skb_success; } - nc = this_cpu_ptr(&napi_alloc_cache); - if (sk_memalloc_socks()) gfp_mask |= __GFP_MEMALLOC; + local_lock_nested_bh(&napi_alloc_cache.bh_lock); + nc = this_cpu_ptr(&napi_alloc_cache); if (NAPI_HAS_SMALL_PAGE_FRAG && len <= SKB_WITH_OVERHEAD(1024)) { /* we are artificially inflating the allocation size, but * that is not as bad as it may look like, as: @@ -832,6 +841,7 @@ struct sk_buff *napi_alloc_skb(struct napi_struct *napi, unsigned int len) data = page_frag_alloc(&nc->page, len, gfp_mask); pfmemalloc = nc->page.pfmemalloc; } + local_unlock_nested_bh(&napi_alloc_cache.bh_lock); if (unlikely(!data)) return NULL; @@ -1393,6 +1403,7 @@ static void napi_skb_cache_put(struct sk_buff *skb) if (!kasan_mempool_poison_object(skb)) return; + guard(local_lock_nested_bh)(&napi_alloc_cache.bh_lock); nc->skb_cache[nc->skb_count++] = skb; if (unlikely(nc->skb_count == NAPI_SKB_CACHE_SIZE)) {