From 6a6cb0fc2f428550eb6dca1204695cc7f0e00a54 Mon Sep 17 00:00:00 2001 Message-Id: <6a6cb0fc2f428550eb6dca1204695cc7f0e00a54.1601675152.git.zanussi@kernel.org> In-Reply-To: <5b5a156f9808b1acf1205606e03da117214549ea.1601675151.git.zanussi@kernel.org> References: <5b5a156f9808b1acf1205606e03da117214549ea.1601675151.git.zanussi@kernel.org> From: Steven Rostedt Date: Tue, 6 Dec 2016 17:50:30 -0500 Subject: [PATCH 204/333] net: Have __napi_schedule_irqoff() disable interrupts on RT Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/4.19/older/patches-4.19.148-rt64.tar.xz A customer hit a crash where the napi sd->poll_list became corrupted. The customer had the bnx2x driver, which does a __napi_schedule_irqoff() in its interrupt handler. Unfortunately, when running with CONFIG_PREEMPT_RT_FULL, this interrupt handler is run as a thread and is preemptable. The call to ____napi_schedule() must be done with interrupts disabled to protect the per cpu softnet_data's "poll_list, which is protected by disabling interrupts (disabling preemption is enough when all interrupts are threaded and local_bh_disable() can't preempt)." As bnx2x isn't the only driver that does this, the safest thing to do is to make __napi_schedule_irqoff() call __napi_schedule() instead when CONFIG_PREEMPT_RT_FULL is enabled, which will call local_irq_save() before calling ____napi_schedule(). Cc: stable-rt@vger.kernel.org Signed-off-by: Steven Rostedt (Red Hat) Signed-off-by: Sebastian Andrzej Siewior --- include/linux/netdevice.h | 12 ++++++++++++ net/core/dev.c | 2 ++ 2 files changed, 14 insertions(+) diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h index 7bf58533f955..0e34e8051ac2 100644 --- a/include/linux/netdevice.h +++ b/include/linux/netdevice.h @@ -422,7 +422,19 @@ typedef enum rx_handler_result rx_handler_result_t; typedef rx_handler_result_t rx_handler_func_t(struct sk_buff **pskb); void __napi_schedule(struct napi_struct *n); + +/* + * When PREEMPT_RT_FULL is defined, all device interrupt handlers + * run as threads, and they can also be preempted (without PREEMPT_RT + * interrupt threads can not be preempted). Which means that calling + * __napi_schedule_irqoff() from an interrupt handler can be preempted + * and can corrupt the napi->poll_list. + */ +#ifdef CONFIG_PREEMPT_RT_FULL +#define __napi_schedule_irqoff(n) __napi_schedule(n) +#else void __napi_schedule_irqoff(struct napi_struct *n); +#endif static inline bool napi_disable_pending(struct napi_struct *n) { diff --git a/net/core/dev.c b/net/core/dev.c index 9b15c663b3f8..b73cbe6c8096 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -5941,6 +5941,7 @@ bool napi_schedule_prep(struct napi_struct *n) } EXPORT_SYMBOL(napi_schedule_prep); +#ifndef CONFIG_PREEMPT_RT_FULL /** * __napi_schedule_irqoff - schedule for receive * @n: entry to schedule @@ -5952,6 +5953,7 @@ void __napi_schedule_irqoff(struct napi_struct *n) ____napi_schedule(this_cpu_ptr(&softnet_data), n); } EXPORT_SYMBOL(__napi_schedule_irqoff); +#endif bool napi_complete_done(struct napi_struct *n, int work_done) { -- 2.17.1