From: Sebastian Andrzej Siewior bigeasy@linutronix.de
[ 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 --- net/core/dev.c | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-)
diff --git a/net/core/dev.c b/net/core/dev.c index 6fd356e72211..9a0c726bd124 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -4723,11 +4723,18 @@ EXPORT_SYMBOL(__napi_schedule); * __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);