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f93524eb9c
If a tracer is invoked before in_nmi() becomes true, the tracer can no
longer detect it is called from NMI context and behave correctly.
Therefore change nmi_{enter,exit}() to use __preempt_count_{add,sub}()
as the normal preempt_count_{add,sub}() have a (desired) function
trace entry.
This fixes a potential issue with the current code; when the function-tracer
has stack-tracing enabled __trace_stack() will malfunction when it hits the
preempt_count_add() function entry from NMI context.
Suggested-by: Steven Rostedt (VMware) <rosted@goodmis.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Reviewed-by: Alexandre Chartre <alexandre.chartre@oracle.com>
Link: https://lkml.kernel.org/r/20200505134101.434193525@linutronix.de
104 lines
2.3 KiB
C
104 lines
2.3 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef LINUX_HARDIRQ_H
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#define LINUX_HARDIRQ_H
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#include <linux/preempt.h>
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#include <linux/lockdep.h>
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#include <linux/ftrace_irq.h>
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#include <linux/vtime.h>
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#include <asm/hardirq.h>
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extern void synchronize_irq(unsigned int irq);
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extern bool synchronize_hardirq(unsigned int irq);
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#if defined(CONFIG_TINY_RCU)
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static inline void rcu_nmi_enter(void)
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{
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}
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static inline void rcu_nmi_exit(void)
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{
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}
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#else
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extern void rcu_nmi_enter(void);
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extern void rcu_nmi_exit(void);
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#endif
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/*
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* It is safe to do non-atomic ops on ->hardirq_context,
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* because NMI handlers may not preempt and the ops are
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* always balanced, so the interrupted value of ->hardirq_context
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* will always be restored.
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*/
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#define __irq_enter() \
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do { \
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account_irq_enter_time(current); \
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preempt_count_add(HARDIRQ_OFFSET); \
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lockdep_hardirq_enter(); \
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} while (0)
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/*
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* Enter irq context (on NO_HZ, update jiffies):
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*/
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extern void irq_enter(void);
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/*
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* Exit irq context without processing softirqs:
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*/
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#define __irq_exit() \
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do { \
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lockdep_hardirq_exit(); \
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account_irq_exit_time(current); \
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preempt_count_sub(HARDIRQ_OFFSET); \
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} while (0)
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/*
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* Exit irq context and process softirqs if needed:
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*/
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extern void irq_exit(void);
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#ifndef arch_nmi_enter
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#define arch_nmi_enter() do { } while (0)
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#define arch_nmi_exit() do { } while (0)
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#endif
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/*
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* NMI vs Tracing
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* --------------
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*
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* We must not land in a tracer until (or after) we've changed preempt_count
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* such that in_nmi() becomes true. To that effect all NMI C entry points must
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* be marked 'notrace' and call nmi_enter() as soon as possible.
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*/
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/*
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* nmi_enter() can nest up to 15 times; see NMI_BITS.
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*/
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#define nmi_enter() \
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do { \
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arch_nmi_enter(); \
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printk_nmi_enter(); \
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lockdep_off(); \
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ftrace_nmi_enter(); \
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BUG_ON(in_nmi() == NMI_MASK); \
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__preempt_count_add(NMI_OFFSET + HARDIRQ_OFFSET); \
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rcu_nmi_enter(); \
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lockdep_hardirq_enter(); \
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} while (0)
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#define nmi_exit() \
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do { \
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lockdep_hardirq_exit(); \
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rcu_nmi_exit(); \
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BUG_ON(!in_nmi()); \
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__preempt_count_sub(NMI_OFFSET + HARDIRQ_OFFSET); \
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ftrace_nmi_exit(); \
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lockdep_on(); \
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printk_nmi_exit(); \
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arch_nmi_exit(); \
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} while (0)
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#endif /* LINUX_HARDIRQ_H */
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