77 lines
2.8 KiB
Diff
77 lines
2.8 KiB
Diff
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From 40bf9203fd467bed110b9943db0300f57780c1cf Mon Sep 17 00:00:00 2001
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From: Steven Rostedt <rostedt@goodmis.org>
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Date: Tue, 6 Dec 2016 17:50:30 -0500
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Subject: [PATCH 240/365] net: Have __napi_schedule_irqoff() disable interrupts
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on RT
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A customer hit a crash where the napi sd->poll_list became corrupted.
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The customer had the bnx2x driver, which does a
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__napi_schedule_irqoff() in its interrupt handler. Unfortunately, when
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running with CONFIG_PREEMPT_RT_FULL, this interrupt handler is run as a
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thread and is preemptable. The call to ____napi_schedule() must be done
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with interrupts disabled to protect the per cpu softnet_data's
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"poll_list, which is protected by disabling interrupts (disabling
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preemption is enough when all interrupts are threaded and
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local_bh_disable() can't preempt)."
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As bnx2x isn't the only driver that does this, the safest thing to do
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is to make __napi_schedule_irqoff() call __napi_schedule() instead when
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CONFIG_PREEMPT_RT_FULL is enabled, which will call local_irq_save()
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before calling ____napi_schedule().
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Cc: stable-rt@vger.kernel.org
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Signed-off-by: Steven Rostedt (Red Hat) <rostedt@goodmis.org>
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Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
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---
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include/linux/netdevice.h | 12 ++++++++++++
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net/core/dev.c | 2 ++
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2 files changed, 14 insertions(+)
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diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
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index c08d3be754fe..f91549292fdc 100644
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--- a/include/linux/netdevice.h
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+++ b/include/linux/netdevice.h
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@@ -396,7 +396,19 @@ typedef enum rx_handler_result rx_handler_result_t;
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typedef rx_handler_result_t rx_handler_func_t(struct sk_buff **pskb);
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void __napi_schedule(struct napi_struct *n);
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+
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+/*
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+ * When PREEMPT_RT_FULL is defined, all device interrupt handlers
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+ * run as threads, and they can also be preempted (without PREEMPT_RT
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+ * interrupt threads can not be preempted). Which means that calling
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+ * __napi_schedule_irqoff() from an interrupt handler can be preempted
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+ * and can corrupt the napi->poll_list.
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+ */
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+#ifdef CONFIG_PREEMPT_RT_FULL
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+#define __napi_schedule_irqoff(n) __napi_schedule(n)
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+#else
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void __napi_schedule_irqoff(struct napi_struct *n);
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+#endif
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static inline bool napi_disable_pending(struct napi_struct *n)
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{
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diff --git a/net/core/dev.c b/net/core/dev.c
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index f1cc73c3cd48..2cb186ecf570 100644
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--- a/net/core/dev.c
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+++ b/net/core/dev.c
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@@ -5008,6 +5008,7 @@ void __napi_schedule(struct napi_struct *n)
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}
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EXPORT_SYMBOL(__napi_schedule);
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+#ifndef CONFIG_PREEMPT_RT_FULL
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/**
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* __napi_schedule_irqoff - schedule for receive
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* @n: entry to schedule
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@@ -5019,6 +5020,7 @@ void __napi_schedule_irqoff(struct napi_struct *n)
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____napi_schedule(this_cpu_ptr(&softnet_data), n);
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}
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EXPORT_SYMBOL(__napi_schedule_irqoff);
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+#endif
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void __napi_complete(struct napi_struct *n)
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{
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--
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2.28.0
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