netdev - [PATCH net-next 1/2] net: Add rtnl_lock

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Message-ID: <152105504019.24797.10144541024701950908.stgit@localhost.localdomain>
Date:   Wed, 14 Mar 2018 22:17:20 +0300
From:   Kirill Tkhai <ktkhai@...tuozzo.com>
To:     davem@...emloft.net, ktkhai@...tuozzo.com, vyasevic@...hat.com,
        edumazet@...gle.com, nicolas.dichtel@...nd.com,
        netdev@...r.kernel.org
Subject: [PATCH net-next 1/2] net: Add rtnl_lock_killable()

rtnl_lock() is widely used mutex in kernel. Some of kernel code
does memory allocations under it. In case of memory deficit this
may invoke OOM killer, but the problem is a killed task can't
exit if it's waiting for the mutex. This may be a reason of deadlock
and panic.

This patch adds a new primitive, which responds on SIGKILL, and
it allows to use it in the places, where we don't want to sleep
forever.

Signed-off-by: Kirill Tkhai <ktkhai@...tuozzo.com>
---
 include/linux/rtnetlink.h |    1 +
 net/core/rtnetlink.c      |    6 ++++++
 2 files changed, 7 insertions(+)

diff --git a/include/linux/rtnetlink.h b/include/linux/rtnetlink.h
index 3573b4bf2fdf..562a175c35a9 100644
--- a/include/linux/rtnetlink.h
+++ b/include/linux/rtnetlink.h
@@ -33,6 +33,7 @@ extern void rtnl_lock(void);
 extern void rtnl_unlock(void);
 extern int rtnl_trylock(void);
 extern int rtnl_is_locked(void);
+extern int rtnl_lock_killable(void);
 
 extern wait_queue_head_t netdev_unregistering_wq;
 extern struct rw_semaphore net_sem;
diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
index 67f375cfb982..87079eaa871b 100644
--- a/net/core/rtnetlink.c
+++ b/net/core/rtnetlink.c
@@ -75,6 +75,12 @@ void rtnl_lock(void)
 }
 EXPORT_SYMBOL(rtnl_lock);
 
+int rtnl_lock_killable(void)
+{
+	return mutex_lock_killable(&rtnl_mutex);
+}
+EXPORT_SYMBOL(rtnl_lock_killable);
+
 static struct sk_buff *defer_kfree_skb_list;
 void rtnl_kfree_skbs(struct sk_buff *head, struct sk_buff *tail)
 {