From patchwork Thu Jun 20 13:21:54 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: 13705503 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 48FAD1AD4B4; Thu, 20 Jun 2024 13:27:33 +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=1718890055; cv=none; b=cdKPk76irtZBlOfHdYpawPTRak1KxCr73bpxBco6jCG/JnTFKgkRyHOHh8e7fElz84oRYF5+fm9RA4zpHUUWx5k8dq5Se01RBXERxK5RJ20ZxocDFTpAmC+/49p4374yZpAzpq29zRlwHwJJZRO8cJDYH1JMj91Jlt/S75albQg= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1718890055; c=relaxed/simple; bh=TUaiPkkM8WJf7rKO603nNckjg49+kh9f/OI9R0157YE=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=BEXR7sTRkhlRCLZKgb30KNXBzQdo+ZFdVlDHVMna3DC2mVktDoRR8zrEbLkrfDF1lhVK/RUjzN2j14cl+56XXqNi3GvjNf1tSx2a8Rj1pU5Tvpd5xIt6M7Lu0VPiH+om+EE5YlhAO6pM1firicoUEEar6yAG8KgmYTgaGf+kPy0= 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=XNa4GuHh; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=jT4KPXDZ; 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="XNa4GuHh"; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="jT4KPXDZ" From: Sebastian Andrzej Siewior DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1718890051; 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=QYWIfeqNspAVknrPforo5Z5uQh9q0Xi+NKd9xdScEZI=; b=XNa4GuHhLFSUwkuwk/0MuKgJRCvVvBZpS+mEi/0gKtAqMywpvPLg5S+h5Ilo4yqw/Luf/X K/b2H+t++vVtvJ60NgZrA1bWwX5D0GpidYc/L0/Zr/kgdcD47nqsikCRUFMZARYTYBJOlg PDa0KGUEd2jIQr6ZyCcK5ZJJammy10BZ/sxAB/rvCwM6mjfOW/Pocqty58KBuig1uH3dLf 53FOW6f7AchEq0iSHqC70vLT5qt6KV33Y5Y8A38N1eEPlhskAma35J26gMb63pbKF2CznK WCPzHQ89k0CrLH8mN3WcwFiJGXeNan7MWFvANAifxmCeAwiHs1Hd+msRGN+KZw== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1718890051; 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=QYWIfeqNspAVknrPforo5Z5uQh9q0Xi+NKd9xdScEZI=; b=jT4KPXDZe44bQ9hvZ6q1TwegY8ADVqSOlATplVq32iOM5cbUM0gwYm0dKDYLe+CirH2h19 ysibj4eLa7giO5CQ== To: linux-kernel@vger.kernel.org, netdev@vger.kernel.org Cc: "David S. Miller" , Daniel Bristot de Oliveira , 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 v9 net-next 04/15] net: Use nested-BH locking for napi_alloc_cache. Date: Thu, 20 Jun 2024 15:21:54 +0200 Message-ID: <20240620132727.660738-5-bigeasy@linutronix.de> In-Reply-To: <20240620132727.660738-1-bigeasy@linutronix.de> References: <20240620132727.660738-1-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 | 29 ++++++++++++++++++++++++----- 1 file changed, 24 insertions(+), 5 deletions(-) diff --git a/net/core/skbuff.c b/net/core/skbuff.c index 1b52f69ad05e2..eb9a7e65b5c81 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. @@ -306,11 +309,16 @@ void napi_get_frags_check(struct napi_struct *napi) void *__napi_alloc_frag_align(unsigned int fragsz, unsigned int align_mask) { struct napi_alloc_cache *nc = this_cpu_ptr(&napi_alloc_cache); + void *data; fragsz = SKB_DATA_ALIGN(fragsz); - return __page_frag_alloc_align(&nc->page, fragsz, GFP_ATOMIC, + local_lock_nested_bh(&napi_alloc_cache.bh_lock); + data = __page_frag_alloc_align(&nc->page, fragsz, GFP_ATOMIC, align_mask); + local_unlock_nested_bh(&napi_alloc_cache.bh_lock); + return data; + } EXPORT_SYMBOL(__napi_alloc_frag_align); @@ -338,16 +346,20 @@ static struct sk_buff *napi_skb_cache_get(void) struct napi_alloc_cache *nc = this_cpu_ptr(&napi_alloc_cache); struct sk_buff *skb; + 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, NAPI_SKB_CACHE_BULK, nc->skb_cache); - if (unlikely(!nc->skb_count)) + if (unlikely(!nc->skb_count)) { + local_unlock_nested_bh(&napi_alloc_cache.bh_lock); return NULL; + } } skb = nc->skb_cache[--nc->skb_count]; + local_unlock_nested_bh(&napi_alloc_cache.bh_lock); kasan_mempool_unpoison_object(skb, kmem_cache_size(net_hotdata.skbuff_cache)); return skb; @@ -740,9 +752,13 @@ 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 +822,11 @@ 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 +848,7 @@ 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; @@ -1431,6 +1448,7 @@ static void napi_skb_cache_put(struct sk_buff *skb) if (!kasan_mempool_poison_object(skb)) return; + 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)) { @@ -1442,6 +1460,7 @@ static void napi_skb_cache_put(struct sk_buff *skb) nc->skb_cache + NAPI_SKB_CACHE_HALF); nc->skb_count = NAPI_SKB_CACHE_HALF; } + local_unlock_nested_bh(&napi_alloc_cache.bh_lock); } void __napi_kfree_skb(struct sk_buff *skb, enum skb_drop_reason reason)