diff options
| author |   Peter Zijlstra <peterz@infradead.org> | 2020-02-12 21:01:16 +0100 |
|---|---|---|
| committer |   Thomas Gleixner <tglx@linutronix.de> | 2020-05-19 15:51:18 +0200 |
| commit | f93524eb9c54f49be150167918f6546b0a2e09b1 (patch) | |
| tree | 2c480d01f1f014baf454abb8ce8f52adac0ad6d4 /include/linux/hardirq.h | |
| parent | sh/ftrace: Move arch_ftrace_nmi_{enter,exit} into nmi exception (diff) | |
| download | linux-dev-f93524eb9c54f49be150167918f6546b0a2e09b1.tar.xz linux-dev-f93524eb9c54f49be150167918f6546b0a2e09b1.zip | |
sched,rcu,tracing: Avoid tracing before in_nmi() is correct
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
Diffstat (limited to 'include/linux/hardirq.h')
| -rw-r--r-- | include/linux/hardirq.h | 13 |
1 files changed, 11 insertions, 2 deletions
diff --git a/include/linux/hardirq.h b/include/linux/hardirq.h index a043ad826c67..621556efe45f 100644 --- a/include/linux/hardirq.h +++ b/include/linux/hardirq.h @@ -66,6 +66,15 @@ extern void irq_exit(void); #endif /* + * NMI vs Tracing + * -------------- + * + * We must not land in a tracer until (or after) we've changed preempt_count + * such that in_nmi() becomes true. To that effect all NMI C entry points must + * be marked 'notrace' and call nmi_enter() as soon as possible. + */ + +/* * nmi_enter() can nest up to 15 times; see NMI_BITS. */ #define nmi_enter() \ @@ -75,7 +84,7 @@ extern void irq_exit(void); lockdep_off(); \ ftrace_nmi_enter(); \ BUG_ON(in_nmi() == NMI_MASK); \ - preempt_count_add(NMI_OFFSET + HARDIRQ_OFFSET); \ + __preempt_count_add(NMI_OFFSET + HARDIRQ_OFFSET); \ rcu_nmi_enter(); \ lockdep_hardirq_enter(); \ } while (0) @@ -85,7 +94,7 @@ extern void irq_exit(void); lockdep_hardirq_exit(); \ rcu_nmi_exit(); \ BUG_ON(!in_nmi()); \ - preempt_count_sub(NMI_OFFSET + HARDIRQ_OFFSET); \ + __preempt_count_sub(NMI_OFFSET + HARDIRQ_OFFSET); \ ftrace_nmi_exit(); \ lockdep_on(); \ printk_nmi_exit(); \ |