tracepoints: add DECLARE_TRACE() and DEFINE_TRACE()

Impact: API *CHANGE*. Must update all tracepoint users.

Add DEFINE_TRACE() to tracepoints to let them declare the tracepoint
structure in a single spot for all the kernel. It helps reducing memory
consumption, especially when declaring a lot of tracepoints, e.g. for
kmalloc tracing.

*API CHANGE WARNING*: now, DECLARE_TRACE() must be used in headers for
tracepoint declarations rather than DEFINE_TRACE(). This is the sane way
to do it. The name previously used was misleading.

Updates scheduler instrumentation to follow this API change.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

2 files changed, 5 insertions, 2 deletions

diff --git a/samples/tracepoints/tp-samples-trace.h b/samples/tracepoints/tp-samples-trace.h
index 0216b55bd640..01724e04c556 100644
--- a/samples/tracepoints/tp-samples-trace.h
+++ b/samples/tracepoints/tp-samples-trace.h
@@ -4,10 +4,10 @@
 #include <linux/proc_fs.h>      /* for struct inode and struct file */
 #include <linux/tracepoint.h>
 
-DEFINE_TRACE(subsys_event,
+DECLARE_TRACE(subsys_event,
         TPPROTO(struct inode *inode, struct file *file),
         TPARGS(inode, file));
-DEFINE_TRACE(subsys_eventb,
+DECLARE_TRACE(subsys_eventb,
         TPPROTO(void),
         TPARGS());
 #endif
diff --git a/samples/tracepoints/tracepoint-sample.c b/samples/tracepoints/tracepoint-sample.c
index 4ae4b7fcc043..00d169792a3e 100644
--- a/samples/tracepoints/tracepoint-sample.c
+++ b/samples/tracepoints/tracepoint-sample.c
@@ -13,6 +13,9 @@
 #include <linux/proc_fs.h>
 #include "tp-samples-trace.h"
 
+DEFINE_TRACE(subsys_event);
+DEFINE_TRACE(subsys_eventb);
+
 struct proc_dir_entry *pentry_example;
 
 static int my_open(struct inode *inode, struct file *file)