rcu: improve RCU CPU stall-warning messages

[safe/jmp/linux-2.6] / kernel / trace / trace.c

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 60de37b..44f916a 100644 (file)
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -33,10 +33,10 @@
 #include <linux/kdebug.h>
 #include <linux/string.h>
 #include <linux/rwsem.h>
+#include <linux/slab.h>
 #include <linux/ctype.h>
 #include <linux/init.h>
 #include <linux/poll.h>
-#include <linux/gfp.h>
 #include <linux/fs.h>
 
 #include "trace.h"
@@ -92,12 +92,12 @@ DEFINE_PER_CPU(int, ftrace_cpu_disabled);
 static inline void ftrace_disable_cpu(void)
 {
        preempt_disable();
-       __this_cpu_inc(per_cpu_var(ftrace_cpu_disabled));
+       __this_cpu_inc(ftrace_cpu_disabled);
 }
 
 static inline void ftrace_enable_cpu(void)
 {
-       __this_cpu_dec(per_cpu_var(ftrace_cpu_disabled));
+       __this_cpu_dec(ftrace_cpu_disabled);
        preempt_enable();
 }
 
@@ -950,6 +950,8 @@ void tracing_start(void)
                goto out;
        }
 
+       /* Prevent the buffers from switching */
+       arch_spin_lock(&ftrace_max_lock);
 
        buffer = global_trace.buffer;
        if (buffer)
@@ -959,6 +961,8 @@ void tracing_start(void)
        if (buffer)
                ring_buffer_record_enable(buffer);
 
+       arch_spin_unlock(&ftrace_max_lock);
+
        ftrace_start();
  out:
        spin_unlock_irqrestore(&tracing_start_lock, flags);
@@ -980,6 +984,9 @@ void tracing_stop(void)
        if (trace_stop_count++)
                goto out;
 
+       /* Prevent the buffers from switching */
+       arch_spin_lock(&ftrace_max_lock);
+
        buffer = global_trace.buffer;
        if (buffer)
                ring_buffer_record_disable(buffer);
@@ -988,6 +995,8 @@ void tracing_stop(void)
        if (buffer)
                ring_buffer_record_disable(buffer);
 
+       arch_spin_unlock(&ftrace_max_lock);
+
  out:
        spin_unlock_irqrestore(&tracing_start_lock, flags);
 }
@@ -1182,7 +1191,7 @@ trace_function(struct trace_array *tr,
        struct ftrace_entry *entry;
 
        /* If we are reading the ring buffer, don't trace */
-       if (unlikely(__this_cpu_read(per_cpu_var(ftrace_cpu_disabled))))
+       if (unlikely(__this_cpu_read(ftrace_cpu_disabled)))
                return;
 
        event = trace_buffer_lock_reserve(buffer, TRACE_FN, sizeof(*entry),
@@ -1275,6 +1284,13 @@ ftrace_trace_userstack(struct ring_buffer *buffer, unsigned long flags, int pc)
        if (!(trace_flags & TRACE_ITER_USERSTACKTRACE))
                return;
 
+       /*
+        * NMIs can not handle page faults, even with fix ups.
+        * The save user stack can (and often does) fault.
+        */
+       if (unlikely(in_nmi()))
+               return;
+
        event = trace_buffer_lock_reserve(buffer, TRACE_USER_STACK,
                                          sizeof(*entry), flags, pc);
        if (!event)