From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 A471A15DBD8; Mon, 27 May 2024 19:08:10 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1716836890; cv=none; b=el5kYZANwcN1w88h5v8NxK2MhnG7WbGW1VkjFm6YjHrA4coGHYXJlkqmxSCThdwfESvwoDbZW1OzCjGgvW8VXqwIEVouRuky5s344w17/LXYR1sPy43hvoyHohlV0S0iJ0K3TsmwuNVKVhewWaRi9oUI/kOM1lo9xHnet72WNKo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1716836890; c=relaxed/simple; bh=4It+bOnKXwMsKtWAqFYU3qjxUCnnVzASZxbehz60ZI0=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=nSXvcxP+CdUnrLlyzpcClJvRBI3QrsfR4JRSfnifeddqakGoqpkr6+guyp5LrtJW527gRnGOZHdqxVp8vdFEN0roZj60wxWdUPrm4uwCC+4E6q3XwQbYd2RSZJdPFqCS1OyYqDN0AK8pgN1GRG4y6D7+3HPE3uyYVWo5GbnmCKI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=T0hLUaWp; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="T0hLUaWp" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3AC92C2BBFC; Mon, 27 May 2024 19:08:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1716836890; bh=4It+bOnKXwMsKtWAqFYU3qjxUCnnVzASZxbehz60ZI0=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=T0hLUaWpLiNAY9Fr5o/VPlNSdxjhTfranq5nu62rPtfeGCadqQc+jtOIRtSDQ7ihO XHumqkeXM9LhG0zBqyshwQI0TPlVnV9EOUPwWLe+RuFuOeXk0Rie5MDCwipnb4JsbG L+F/whu68qDLbTml5+3MVjdnxc1qeRIbqqL0y9xM= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Eric Dumazet , Jiri Pirko , "David S. Miller" , Sasha Levin Subject: [PATCH 6.9 186/427] net: give more chances to rcu in netdev_wait_allrefs_any() Date: Mon, 27 May 2024 20:53:53 +0200 Message-ID: <20240527185619.590663096@linuxfoundation.org> X-Mailer: git-send-email 2.45.1 In-Reply-To: <20240527185601.713589927@linuxfoundation.org> References: <20240527185601.713589927@linuxfoundation.org> User-Agent: quilt/0.67 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.9-stable review patch. If anyone has any objections, please let me know. ------------------ From: Eric Dumazet [ Upstream commit cd42ba1c8ac9deb9032add6adf491110e7442040 ] This came while reviewing commit c4e86b4363ac ("net: add two more call_rcu_hurry()"). Paolo asked if adding one synchronize_rcu() would help. While synchronize_rcu() does not help, making sure to call rcu_barrier() before msleep(wait) is definitely helping to make sure lazy call_rcu() are completed. Instead of waiting ~100 seconds in my tests, the ref_tracker splats occurs one time only, and netdev_wait_allrefs_any() latency is reduced to the strict minimum. Ideally we should audit our call_rcu() users to make sure no refcount (or cascading call_rcu()) is held too long, because rcu_barrier() is quite expensive. Fixes: 0e4be9e57e8c ("net: use exponential backoff in netdev_wait_allrefs") Signed-off-by: Eric Dumazet Link: https://lore.kernel.org/all/28bbf698-befb-42f6-b561-851c67f464aa@kernel.org/T/#m76d73ed6b03cd930778ac4d20a777f22a08d6824 Reviewed-by: Jiri Pirko Signed-off-by: David S. Miller Signed-off-by: Sasha Levin --- net/core/dev.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/net/core/dev.c b/net/core/dev.c index 331848eca7d31..e8fb4ef8a85f8 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -10488,8 +10488,9 @@ static struct net_device *netdev_wait_allrefs_any(struct list_head *list) rebroadcast_time = jiffies; } + rcu_barrier(); + if (!wait) { - rcu_barrier(); wait = WAIT_REFS_MIN_MSECS; } else { msleep(wait); -- 2.43.0