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

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[ Upstream commit 8380c81d5c4fced6f4397795a5ae65758272bbfd ]

__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: Juri Lelli <juri.lelli@redhat.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Juri Lelli <juri.lelli@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Sebastian Andrzej Siewior 2021-05-12 23:43:24 +02:00 committed by Greg Kroah-Hartman
parent bdf5334250
commit 45cc7a653f
1 changed files with 9 additions and 2 deletions
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11
net/core/dev.c
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@ -5972,11 +5972,18 @@ 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)
{
____napi_schedule(this_cpu_ptr(&softnet_data), n);
if (!IS_ENABLED(CONFIG_PREEMPT_RT))
____napi_schedule(this_cpu_ptr(&softnet_data), n);
else
__napi_schedule(n);
}
EXPORT_SYMBOL(__napi_schedule_irqoff);