linux-kernel - [PATCH net-next] net: link_watch: prevent starvation when processing linkwatch wq

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Message-ID: <1558921674-158349-1-git-send-email-linyunsheng@huawei.com>
Date:   Mon, 27 May 2019 09:47:54 +0800
From:   Yunsheng Lin <linyunsheng@...wei.com>
To:     <davem@...emloft.net>
CC:     <hkallweit1@...il.com>, <f.fainelli@...il.com>,
        <netdev@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <linuxarm@...wei.com>
Subject: [PATCH net-next] net: link_watch: prevent starvation when processing linkwatch wq

When user has configured a large number of virtual netdev, such
as 4K vlans, the carrier on/off operation of the real netdev
will also cause it's virtual netdev's link state to be processed
in linkwatch. Currently, the processing is done in a work queue,
which may cause worker starvation problem for other work queue.

This patch releases the cpu when link watch worker has processed
a fixed number of netdev' link watch event, and schedule the
work queue again when there is still link watch event remaining.

Signed-off-by: Yunsheng Lin <linyunsheng@...wei.com>
---
 net/core/link_watch.c | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/net/core/link_watch.c b/net/core/link_watch.c
index 7f51efb..06276ff 100644
--- a/net/core/link_watch.c
+++ b/net/core/link_watch.c
@@ -168,9 +168,16 @@ static void linkwatch_do_dev(struct net_device *dev)
 
 static void __linkwatch_run_queue(int urgent_only)
 {
+#define MAX_DO_DEV_PER_LOOP	100
+
+	int do_dev = MAX_DO_DEV_PER_LOOP;
 	struct net_device *dev;
 	LIST_HEAD(wrk);
 
+	/* Give urgent case more budget */
+	if (urgent_only)
+		do_dev += MAX_DO_DEV_PER_LOOP;
+
 	/*
 	 * Limit the number of linkwatch events to one
 	 * per second so that a runaway driver does not
@@ -189,7 +196,7 @@ static void __linkwatch_run_queue(int urgent_only)
 	spin_lock_irq(&lweventlist_lock);
 	list_splice_init(&lweventlist, &wrk);
 
-	while (!list_empty(&wrk)) {
+	while (!list_empty(&wrk) && do_dev > 0) {
 
 		dev = list_first_entry(&wrk, struct net_device, link_watch_list);
 		list_del_init(&dev->link_watch_list);
@@ -201,8 +208,13 @@ static void __linkwatch_run_queue(int urgent_only)
 		spin_unlock_irq(&lweventlist_lock);
 		linkwatch_do_dev(dev);
 		spin_lock_irq(&lweventlist_lock);
+
+		do_dev--;
 	}
 
+	/* Add the remaining work back to lweventlist */
+	list_splice_init(&wrk, &lweventlist);
+
 	if (!list_empty(&lweventlist))
 		linkwatch_schedule_work(0);
 	spin_unlock_irq(&lweventlist_lock);
-- 
2.8.1