linux-kernel - [PATCH] netpoll: don't require irqs disabled in rt kernels

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Message-Id: <20210531152325.36671-1-wander@redhat.com>
Date:   Mon, 31 May 2021 12:23:23 -0300
From:   wander@...hat.com
To:     unlisted-recipients:; (no To-header on input)
Cc:     linux-rt-users@...r.kernel.org, bigeasy@...utronix.de,
        tglx@...utronix.de, rostedt@...dmis.org,
        Wander Lairson Costa <wander@...hat.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Florian Fainelli <f.fainelli@...il.com>,
        Andrew Lunn <andrew@...n.ch>,
        Vladimir Oltean <vladimir.oltean@....com>,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] netpoll: don't require irqs disabled in rt kernels

From: Wander Lairson Costa <wander@...hat.com>

write_msg(netconsole.c:836) calls netpoll_send_udp after a call to
spin_lock_irqsave, which normally disables interrupts; but in PREEMPT_RT
this call just locks an rt_mutex without disabling irqs. In this case,
netpoll_send_udp is called with interrupts enabled.

Signed-off-by: Wander Lairson Costa <wander@...hat.com>
---
 net/core/netpoll.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/net/core/netpoll.c b/net/core/netpoll.c
index c310c7c1cef7..0a6b04714558 100644
--- a/net/core/netpoll.c
+++ b/net/core/netpoll.c
@@ -36,6 +36,7 @@
 #include <net/ip6_checksum.h>
 #include <asm/unaligned.h>
 #include <trace/events/napi.h>
+#include <linux/kconfig.h>
 
 /*
  * We maintain a small pool of fully-sized skbs, to make sure the
@@ -389,7 +390,8 @@ void netpoll_send_udp(struct netpoll *np, const char *msg, int len)
 	static atomic_t ip_ident;
 	struct ipv6hdr *ip6h;
 
-	WARN_ON_ONCE(!irqs_disabled());
+	if (!IS_ENABLED(CONFIG_PREEMPT_RT))
+		WARN_ON_ONCE(!irqs_disabled());
 
 	udp_len = len + sizeof(*udph);
 	if (np->ipv6)
-- 
2.27.0