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

From: Wander Lairson Costa <redacted>

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 <redacted>
---
 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

Hello:

This patch was applied to netdev/net-next.git (refs/heads/master):

On Mon, 31 May 2021 12:23:23 -0300 you wrote:

From: Wander Lairson Costa <redacted>

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.

[...]

Here is the summary with links:
  - netpoll: don't require irqs disabled in rt kernels
    https://git.kernel.org/netdev/net-next/c/b0f6c9ac8088

You are awesome, thank you!
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