1 files changed, 76 insertions, 4 deletions

diff --git a/include/linux/kernel.h b/include/linux/kernel.h
index 08bf5da86676..4e726b9a71ec 100644
--- a/include/linux/kernel.h
+++ b/include/linux/kernel.h
@@ -242,6 +242,19 @@ extern struct ratelimit_state printk_ratelimit_state;
 extern int printk_ratelimit(void);
 extern bool printk_timed_ratelimit(unsigned long *caller_jiffies,
                                    unsigned int interval_msec);
+
+/*
+ * Print a one-time message (analogous to WARN_ONCE() et al):
+ */
+#define printk_once(x...) ({                    \
+        static int __print_once = 1;            \
+                                                \
+        if (__print_once) {                     \
+                __print_once = 0;               \
+                printk(x);                      \
+        }                                       \
+})
+
 #else
 static inline int vprintk(const char *s, va_list args)
         __attribute__ ((format (printf, 1, 0)));
@@ -253,6 +266,10 @@ static inline int printk_ratelimit(void) { return 0; }
 static inline bool printk_timed_ratelimit(unsigned long *caller_jiffies, \
                                           unsigned int interval_msec)   \
                 { return false; }
+
+/* No effect, but we still get type checking even in the !PRINTK case: */
+#define printk_once(x...) printk(x)
+
 #endif
 
 extern int printk_needs_cpu(int cpu);
@@ -369,8 +386,35 @@ static inline char *pack_hex_byte(char *buf, u8 byte)
 
 /*
  * General tracing related utility functions - trace_printk(),
- * tracing_start()/tracing_stop:
+ * tracing_on/tracing_off and tracing_start()/tracing_stop
+ *
+ * Use tracing_on/tracing_off when you want to quickly turn on or off
+ * tracing. It simply enables or disables the recording of the trace events.
+ * This also corresponds to the user space debugfs/tracing/tracing_on
+ * file, which gives a means for the kernel and userspace to interact.
+ * Place a tracing_off() in the kernel where you want tracing to end.
+ * From user space, examine the trace, and then echo 1 > tracing_on
+ * to continue tracing.
+ *
+ * tracing_stop/tracing_start has slightly more overhead. It is used
+ * by things like suspend to ram where disabling the recording of the
+ * trace is not enough, but tracing must actually stop because things
+ * like calling smp_processor_id() may crash the system.
+ *
+ * Most likely, you want to use tracing_on/tracing_off.
  */
+#ifdef CONFIG_RING_BUFFER
+void tracing_on(void);
+void tracing_off(void);
+/* trace_off_permanent stops recording with no way to bring it back */
+void tracing_off_permanent(void);
+int tracing_is_on(void);
+#else
+static inline void tracing_on(void) { }
+static inline void tracing_off(void) { }
+static inline void tracing_off_permanent(void) { }
+static inline int tracing_is_on(void) { return 0; }
+#endif
 #ifdef CONFIG_TRACING
 extern void tracing_start(void);
 extern void tracing_stop(void);
@@ -379,6 +423,16 @@ extern void ftrace_off_permanent(void);
 extern void
 ftrace_special(unsigned long arg1, unsigned long arg2, unsigned long arg3);
 
+static inline void __attribute__ ((format (printf, 1, 2)))
+____trace_printk_check_format(const char *fmt, ...)
+{
+}
+#define __trace_printk_check_format(fmt, args...)                       \
+do {                                                                    \
+        if (0)                                                          \
+                ____trace_printk_check_format(fmt, ##args);             \
+} while (0)
+
 /**
  * trace_printk - printf formatting in the ftrace buffer
  * @fmt: the printf format for printing
@@ -395,13 +449,31 @@ ftrace_special(unsigned long arg1, unsigned long arg2, unsigned long arg3);
  * Please refrain from leaving trace_printks scattered around in
  * your code.
  */
-# define trace_printk(fmt...) __trace_printk(_THIS_IP_, fmt)
+
+#define trace_printk(fmt, args...)                                      \
+do {                                                                    \
+        static const char *trace_printk_fmt                             \
+        __attribute__((section("__trace_printk_fmt")));                 \
+        trace_printk_fmt = fmt;                                 \
+        __trace_printk_check_format(fmt, ##args);                       \
+        __trace_printk(_THIS_IP_, trace_printk_fmt, ##args);            \
+} while (0)
+
 extern int
 __trace_printk(unsigned long ip, const char *fmt, ...)
         __attribute__ ((format (printf, 2, 3)));
-# define ftrace_vprintk(fmt, ap) __trace_printk(_THIS_IP_, fmt, ap)
+
+#define ftrace_vprintk(fmt, vargs)                                      \
+do {                                                                    \
+        static const char *trace_printk_fmt                             \
+        __attribute__((section("__trace_printk_fmt")));                 \
+        trace_printk_fmt = fmt;                                 \
+        __ftrace_vprintk(_THIS_IP_, trace_printk_fmt, vargs);           \
+} while (0)
+
 extern int
 __ftrace_vprintk(unsigned long ip, const char *fmt, va_list ap);
+
 extern void ftrace_dump(void);
 #else
 static inline void
@@ -423,7 +495,7 @@ ftrace_vprintk(const char *fmt, va_list ap)
         return 0;
 }
 static inline void ftrace_dump(void) { }
-#endif
+#endif /* CONFIG_TRACING */
 
 /*
  *      Display an IP address in readable format.