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authorMathieu Desnoyers <mathieu.desnoyers@polymtl.ca>2008-02-13 18:03:37 -0500
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2008-02-13 19:21:20 -0500
commitfb40bd78b0f91b274879cf5db8facd1e04b6052e (patch)
tree2347ccb5ad07f58ab5a4eb41174bb7b54d5f0c5b /samples/markers
parent9170d2f6e1dc4d79650fbf492d1cd45291c66504 (diff)
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>
Diffstat (limited to 'samples/markers')
-rw-r--r--samples/markers/probe-example.c25
1 files changed, 9 insertions, 16 deletions
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 {
20 marker_probe_func *probe_func; 20 marker_probe_func *probe_func;
21}; 21};
22 22
23void probe_subsystem_event(const struct marker *mdata, void *private, 23void probe_subsystem_event(void *probe_data, void *call_data,
24 const char *format, ...) 24 const char *format, va_list *args)
25{ 25{
26 va_list ap;
27 /* Declare args */ 26 /* Declare args */
28 unsigned int value; 27 unsigned int value;
29 const char *mystr; 28 const char *mystr;
30 29
31 /* Assign args */ 30 /* Assign args */
32 va_start(ap, format); 31 value = va_arg(*args, typeof(value));
33 value = va_arg(ap, typeof(value)); 32 mystr = va_arg(*args, typeof(mystr));
34 mystr = va_arg(ap, typeof(mystr));
35 33
36 /* Call printk */ 34 /* Call printk */
37 printk(KERN_DEBUG "Value %u, string %s\n", value, mystr); 35 printk(KERN_INFO "Value %u, string %s\n", value, mystr);
38 36
39 /* or count, check rights, serialize data in a buffer */ 37 /* or count, check rights, serialize data in a buffer */
40
41 va_end(ap);
42} 38}
43 39
44atomic_t eventb_count = ATOMIC_INIT(0); 40atomic_t eventb_count = ATOMIC_INIT(0);
45 41
46void probe_subsystem_eventb(const struct marker *mdata, void *private, 42void probe_subsystem_eventb(void *probe_data, void *call_data,
47 const char *format, ...) 43 const char *format, va_list *args)
48{ 44{
49 /* Increment counter */ 45 /* Increment counter */
50 atomic_inc(&eventb_count); 46 atomic_inc(&eventb_count);
@@ -72,10 +68,6 @@ static int __init probe_init(void)
72 if (result) 68 if (result)
73 printk(KERN_INFO "Unable to register probe %s\n", 69 printk(KERN_INFO "Unable to register probe %s\n",
74 probe_array[i].name); 70 probe_array[i].name);
75 result = marker_arm(probe_array[i].name);
76 if (result)
77 printk(KERN_INFO "Unable to arm probe %s\n",
78 probe_array[i].name);
79 } 71 }
80 return 0; 72 return 0;
81} 73}
@@ -85,7 +77,8 @@ static void __exit probe_fini(void)
85 int i; 77 int i;
86 78
87 for (i = 0; i < ARRAY_SIZE(probe_array); i++) 79 for (i = 0; i < ARRAY_SIZE(probe_array); i++)
88 marker_probe_unregister(probe_array[i].name); 80 marker_probe_unregister(probe_array[i].name,
81 probe_array[i].probe_func, &probe_array[i]);
89 printk(KERN_INFO "Number of event b : %u\n", 82 printk(KERN_INFO "Number of event b : %u\n",
90 atomic_read(&eventb_count)); 83 atomic_read(&eventb_count));
91} 84}