From fb40bd78b0f91b274879cf5db8facd1e04b6052e Mon Sep 17 00:00:00 2001 From: Mathieu Desnoyers Date: Wed, 13 Feb 2008 15:03:37 -0800 Subject: 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 Cc: Christoph Hellwig Cc: Mike Mason Cc: Dipankar Sarma Cc: David Smith Cc: "Paul E. McKenney" Cc: "Frank Ch. Eigler" Cc: Steven Rostedt Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- samples/markers/probe-example.c | 25 +++++++++---------------- 1 file changed, 9 insertions(+), 16 deletions(-) (limited to 'samples') diff --git a/samples/markers/probe-example.c b/samples/markers/probe-example.c index a36797535615..c8e099d4d1fd 100644 --- a/samples/markers/probe-example.c +++ b/samples/markers/probe-example.c @@ -20,31 +20,27 @@ struct probe_data { 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 @@ static int __init probe_init(void) 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 @@ static void __exit probe_fini(void) 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)); } -- cgit v1.2.3-59-g8ed1b