net: Treat __napi_schedule_irqoff() as __napi_schedule() on PREEMPT_RT

stable inclusion
from stable-5.10.51
commit 3393405257ed27f5b13b75faf1842e1b083c6f7b
bugzilla: 175263 https://gitee.com/openeuler/kernel/issues/I4DT6F

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=3393405257ed27f5b13b75faf1842e1b083c6f7b

--------------------------------

[ Upstream commit 8380c81d ]

__napi_schedule_irqoff() is an optimized version of __napi_schedule()
which can be used where it is known that interrupts are disabled,
e.g. in interrupt-handlers, spin_lock_irq() sections or hrtimer
callbacks.

On PREEMPT_RT enabled kernels this assumptions is not true. Force-
threaded interrupt handlers and spinlocks are not disabling interrupts
and the NAPI hrtimer callback is forced into softirq context which runs
with interrupts enabled as well.

Chasing all usage sites of __napi_schedule_irqoff() is a whack-a-mole
game so make __napi_schedule_irqoff() invoke __napi_schedule() for
PREEMPT_RT kernels.

The callers of ____napi_schedule() in the networking core have been
audited and are correct on PREEMPT_RT kernels as well.
Reported-by: NJuri Lelli <juri.lelli@redhat.com>
Signed-off-by: NSebastian Andrzej Siewior <bigeasy@linutronix.de>
Reviewed-by: NThomas Gleixner <tglx@linutronix.de>
Reviewed-by: NJuri Lelli <juri.lelli@redhat.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>
Signed-off-by: NSasha Levin <sashal@kernel.org>
Signed-off-by: NChen Jun <chenjun102@huawei.com>
Acked-by: NWeilong Chen <chenweilong@huawei.com>
Signed-off-by: NChen Jun <chenjun102@huawei.com>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>

net/core/dev.c

@@ -6433,11 +6433,18 @@ EXPORT_SYMBOL(napi_schedule_prep);
  * __napi_schedule_irqoff - schedule for receive
  * @n: entry to schedule
  *
- * Variant of __napi_schedule() assuming hard irqs are masked
+ * Variant of __napi_schedule() assuming hard irqs are masked.
+ *
+ * On PREEMPT_RT enabled kernels this maps to __napi_schedule()
+ * because the interrupt disabled assumption might not be true
+ * due to force-threaded interrupts and spinlock substitution.
  */
 void __napi_schedule_irqoff(struct napi_struct *n)
 {
+	if (!IS_ENABLED(CONFIG_PREEMPT_RT))
 		____napi_schedule(this_cpu_ptr(&softnet_data), n);
+	else
+		__napi_schedule(n);
 }
 EXPORT_SYMBOL(__napi_schedule_irqoff);