Linux Kernel Markers: support multiple probes
RCU style multiple probes support for the Linux Kernel Markers. Common case
(one probe) is still fast and does not require dynamic allocation or a
supplementary pointer dereference on the fast path.
- Move preempt disable from the marker site to the callback.
Since we now have an internal callback, move the preempt disable/enable to the
callback instead of the marker site.
Since the callback change is done asynchronously (passing from a handler that
supports arguments to a handler that does not setup the arguments is no
arguments are passed), we can safely update it even if it is outside the
preempt disable section.
- Move probe arm to probe connection. Now, a connected probe is automatically
armed.
Remove MARK_MAX_FORMAT_LEN, unused.
This patch modifies the Linux Kernel Markers API : it removes the probe
"arm/disarm" and changes the probe function prototype : it now expects a
va_list * instead of a "...".
If we want to have more than one probe connected to a marker at a given
time (LTTng, or blktrace, ssytemtap) then we need this patch. Without it,
connecting a second probe handler to a marker will fail.
It allow us, for instance, to do interesting combinations :
Do standard tracing with LTTng and, eventually, to compute statistics
with SystemTAP, or to have a special trigger on an event that would call
a systemtap script which would stop flight recorder tracing.
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Mike Mason <mmlnx@us.ibm.com>
Cc: Dipankar Sarma <dipankar@in.ibm.com>
Cc: David Smith <dsmith@redhat.com>
Cc: "Paul E. McKenney" <paulmck@us.ibm.com>
Cc: "Frank Ch. Eigler" <fche@redhat.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/include/linux/marker.h b/include/linux/marker.h
index 5f36cf9..b5f9563 100644
--- a/include/linux/marker.h
+++ b/include/linux/marker.h
@@ -19,16 +19,23 @@
/**
* marker_probe_func - Type of a marker probe function
- * @mdata: pointer of type struct marker
- * @private_data: caller site private data
+ * @probe_private: probe private data
+ * @call_private: call site private data
* @fmt: format string
- * @...: variable argument list
+ * @args: variable argument list pointer. Use a pointer to overcome C's
+ * inability to pass this around as a pointer in a portable manner in
+ * the callee otherwise.
*
* Type of marker probe functions. They receive the mdata and need to parse the
* format string to recover the variable argument list.
*/
-typedef void marker_probe_func(const struct marker *mdata,
- void *private_data, const char *fmt, ...);
+typedef void marker_probe_func(void *probe_private, void *call_private,
+ const char *fmt, va_list *args);
+
+struct marker_probe_closure {
+ marker_probe_func *func; /* Callback */
+ void *probe_private; /* Private probe data */
+};
struct marker {
const char *name; /* Marker name */
@@ -36,8 +43,11 @@
* variable argument list.
*/
char state; /* Marker state. */
- marker_probe_func *call;/* Probe handler function pointer */
- void *private; /* Private probe data */
+ char ptype; /* probe type : 0 : single, 1 : multi */
+ void (*call)(const struct marker *mdata, /* Probe wrapper */
+ void *call_private, const char *fmt, ...);
+ struct marker_probe_closure single;
+ struct marker_probe_closure *multi;
} __attribute__((aligned(8)));
#ifdef CONFIG_MARKERS
@@ -49,7 +59,7 @@
* not add unwanted padding between the beginning of the section and the
* structure. Force alignment to the same alignment as the section start.
*/
-#define __trace_mark(name, call_data, format, args...) \
+#define __trace_mark(name, call_private, format, args...) \
do { \
static const char __mstrtab_name_##name[] \
__attribute__((section("__markers_strings"))) \
@@ -60,24 +70,23 @@
static struct marker __mark_##name \
__attribute__((section("__markers"), aligned(8))) = \
{ __mstrtab_name_##name, __mstrtab_format_##name, \
- 0, __mark_empty_function, NULL }; \
+ 0, 0, marker_probe_cb, \
+ { __mark_empty_function, NULL}, NULL }; \
__mark_check_format(format, ## args); \
if (unlikely(__mark_##name.state)) { \
- preempt_disable(); \
(*__mark_##name.call) \
- (&__mark_##name, call_data, \
+ (&__mark_##name, call_private, \
format, ## args); \
- preempt_enable(); \
} \
} while (0)
extern void marker_update_probe_range(struct marker *begin,
- struct marker *end, struct module *probe_module, int *refcount);
+ struct marker *end);
#else /* !CONFIG_MARKERS */
-#define __trace_mark(name, call_data, format, args...) \
+#define __trace_mark(name, call_private, format, args...) \
__mark_check_format(format, ## args)
static inline void marker_update_probe_range(struct marker *begin,
- struct marker *end, struct module *probe_module, int *refcount)
+ struct marker *end)
{ }
#endif /* CONFIG_MARKERS */
@@ -92,8 +101,6 @@
#define trace_mark(name, format, args...) \
__trace_mark(name, NULL, format, ## args)
-#define MARK_MAX_FORMAT_LEN 1024
-
/**
* MARK_NOARGS - Format string for a marker with no argument.
*/
@@ -106,24 +113,30 @@
extern marker_probe_func __mark_empty_function;
+extern void marker_probe_cb(const struct marker *mdata,
+ void *call_private, const char *fmt, ...);
+extern void marker_probe_cb_noarg(const struct marker *mdata,
+ void *call_private, const char *fmt, ...);
+
/*
* Connect a probe to a marker.
* private data pointer must be a valid allocated memory address, or NULL.
*/
extern int marker_probe_register(const char *name, const char *format,
- marker_probe_func *probe, void *private);
+ marker_probe_func *probe, void *probe_private);
/*
* Returns the private data given to marker_probe_register.
*/
-extern void *marker_probe_unregister(const char *name);
+extern int marker_probe_unregister(const char *name,
+ marker_probe_func *probe, void *probe_private);
/*
* Unregister a marker by providing the registered private data.
*/
-extern void *marker_probe_unregister_private_data(void *private);
+extern int marker_probe_unregister_private_data(marker_probe_func *probe,
+ void *probe_private);
-extern int marker_arm(const char *name);
-extern int marker_disarm(const char *name);
-extern void *marker_get_private_data(const char *name);
+extern void *marker_get_private_data(const char *name, marker_probe_func *probe,
+ int num);
#endif