sched: do not account for NMIs

Impact: avoid corruption in system time accounting

Martin Schwidefsky told me that there was an issue with NMIs and
system accounting. The problem is that the accounting code is
not reentrant, and if an NMI goes off after an interrupt it can
corrupt the accounting.

For now, the best we can do is to treat NMIs like SMIs and they
are not accounted for.

This patch changes nmi_enter to not call __irq_enter and to do
the preempt-count and tracing calls directly.

Signed-off-by: Steven Rostedt <srostedt@redhat.com>

diff --git a/include/linux/hardirq.h b/include/linux/hardirq.h
index 9841221f53f2e73b055edad8a1bf59b3b455b9c7..faa1cf848bcd38e5c59725c3c0bb3e7bfdf86f63 100644 (file)
--- a/include/linux/hardirq.h
+++ b/include/linux/hardirq.h
@@ -175,24 +175,24 @@ extern void irq_enter(void);
  */
 extern void irq_exit(void);
 
-#define nmi_enter()                            \
-       do {                                    \
-               ftrace_nmi_enter();             \
-               BUG_ON(in_nmi());               \
-               add_preempt_count(NMI_OFFSET);  \
-               lockdep_off();                  \
-               rcu_nmi_enter();                \
-               __irq_enter();                  \
+#define nmi_enter()                                            \
+       do {                                                    \
+               ftrace_nmi_enter();                             \
+               BUG_ON(in_nmi());                               \
+               add_preempt_count(NMI_OFFSET + HARDIRQ_OFFSET); \
+               lockdep_off();                                  \
+               rcu_nmi_enter();                                \
+               trace_hardirq_enter();                          \
        } while (0)
 
-#define nmi_exit()                             \
-       do {                                    \
-               __irq_exit();                   \
-               rcu_nmi_exit();                 \
-               lockdep_on();                   \
-               BUG_ON(!in_nmi());              \
-               sub_preempt_count(NMI_OFFSET);  \
-               ftrace_nmi_exit();              \
+#define nmi_exit()                                             \
+       do {                                                    \
+               trace_hardirq_exit();                           \
+               rcu_nmi_exit();                                 \
+               lockdep_on();                                   \
+               BUG_ON(!in_nmi());                              \
+               sub_preempt_count(NMI_OFFSET + HARDIRQ_OFFSET); \
+               ftrace_nmi_exit();                              \
        } while (0)
 
 #endif /* LINUX_HARDIRQ_H */