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/samples/markers/probe-example.c b/samples/markers/probe-example.c
index a367975..c8e099d 100644
--- a/samples/markers/probe-example.c
+++ b/samples/markers/probe-example.c
@@ -20,31 +20,27 @@
marker_probe_func *probe_func;
};
-void probe_subsystem_event(const struct marker *mdata, void *private,
- const char *format, ...)
+void probe_subsystem_event(void *probe_data, void *call_data,
+ const char *format, va_list *args)
{
- va_list ap;
/* Declare args */
unsigned int value;
const char *mystr;
/* Assign args */
- va_start(ap, format);
- value = va_arg(ap, typeof(value));
- mystr = va_arg(ap, typeof(mystr));
+ value = va_arg(*args, typeof(value));
+ mystr = va_arg(*args, typeof(mystr));
/* Call printk */
- printk(KERN_DEBUG "Value %u, string %s\n", value, mystr);
+ printk(KERN_INFO "Value %u, string %s\n", value, mystr);
/* or count, check rights, serialize data in a buffer */
-
- va_end(ap);
}
atomic_t eventb_count = ATOMIC_INIT(0);
-void probe_subsystem_eventb(const struct marker *mdata, void *private,
- const char *format, ...)
+void probe_subsystem_eventb(void *probe_data, void *call_data,
+ const char *format, va_list *args)
{
/* Increment counter */
atomic_inc(&eventb_count);
@@ -72,10 +68,6 @@
if (result)
printk(KERN_INFO "Unable to register probe %s\n",
probe_array[i].name);
- result = marker_arm(probe_array[i].name);
- if (result)
- printk(KERN_INFO "Unable to arm probe %s\n",
- probe_array[i].name);
}
return 0;
}
@@ -85,7 +77,8 @@
int i;
for (i = 0; i < ARRAY_SIZE(probe_array); i++)
- marker_probe_unregister(probe_array[i].name);
+ marker_probe_unregister(probe_array[i].name,
+ probe_array[i].probe_func, &probe_array[i]);
printk(KERN_INFO "Number of event b : %u\n",
atomic_read(&eventb_count));
}