netdev - [PATCH net-next 03/18] ipv4/route: Use this_cpu_inc() for stats on PREEMPT

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Message-ID: <20250309144653.825351-4-bigeasy@linutronix.de>
Date: Sun,  9 Mar 2025 15:46:38 +0100
From: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To: netdev@...r.kernel.org,
	linux-rt-devel@...ts.linux.dev
Cc: "David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>,
	Paolo Abeni <pabeni@...hat.com>,
	Simon Horman <horms@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
	David Ahern <dsahern@...nel.org>
Subject: [PATCH net-next 03/18] ipv4/route: Use this_cpu_inc() for stats on PREEMPT_RT.

The statistics are incremented with raw_cpu_inc() assuming it always
happens with bottom half disabled. Without per-CPU locking in
local_bh_disable() on PREEMPT_RT this is no longer true.

Use this_cpu_inc() on PREEMPT_RT for the increment to not worry about
preemption.

Cc: David Ahern <dsahern@...nel.org>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
---
 net/ipv4/route.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index 753704f75b2c6..5d7c7efea66cc 100644
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -189,7 +189,11 @@ const __u8 ip_tos2prio[16] = {
 EXPORT_SYMBOL(ip_tos2prio);
 
 static DEFINE_PER_CPU(struct rt_cache_stat, rt_cache_stat);
+#ifndef CONFIG_PREEMPT_RT
 #define RT_CACHE_STAT_INC(field) raw_cpu_inc(rt_cache_stat.field)
+#else
+#define RT_CACHE_STAT_INC(field) this_cpu_inc(rt_cache_stat.field)
+#endif
 
 #ifdef CONFIG_PROC_FS
 static void *rt_cache_seq_start(struct seq_file *seq, loff_t *pos)
-- 
2.47.2