fb40bd78b0
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>
92 lines
2.0 KiB
C
92 lines
2.0 KiB
C
/* probe-example.c
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*
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* Connects two functions to marker call sites.
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*
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* (C) Copyright 2007 Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
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*
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* This file is released under the GPLv2.
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* See the file COPYING for more details.
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*/
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#include <linux/sched.h>
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#include <linux/kernel.h>
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#include <linux/module.h>
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#include <linux/marker.h>
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#include <asm/atomic.h>
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struct probe_data {
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const char *name;
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const char *format;
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marker_probe_func *probe_func;
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};
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void probe_subsystem_event(void *probe_data, void *call_data,
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const char *format, va_list *args)
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{
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/* Declare args */
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unsigned int value;
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const char *mystr;
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/* Assign args */
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value = va_arg(*args, typeof(value));
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mystr = va_arg(*args, typeof(mystr));
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/* Call printk */
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printk(KERN_INFO "Value %u, string %s\n", value, mystr);
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/* or count, check rights, serialize data in a buffer */
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}
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atomic_t eventb_count = ATOMIC_INIT(0);
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void probe_subsystem_eventb(void *probe_data, void *call_data,
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const char *format, va_list *args)
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{
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/* Increment counter */
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atomic_inc(&eventb_count);
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}
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static struct probe_data probe_array[] =
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{
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{ .name = "subsystem_event",
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.format = "integer %d string %s",
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.probe_func = probe_subsystem_event },
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{ .name = "subsystem_eventb",
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.format = MARK_NOARGS,
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.probe_func = probe_subsystem_eventb },
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};
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static int __init probe_init(void)
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{
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int result;
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int i;
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for (i = 0; i < ARRAY_SIZE(probe_array); i++) {
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result = marker_probe_register(probe_array[i].name,
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probe_array[i].format,
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probe_array[i].probe_func, &probe_array[i]);
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if (result)
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printk(KERN_INFO "Unable to register probe %s\n",
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probe_array[i].name);
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}
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return 0;
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}
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static void __exit probe_fini(void)
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{
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int i;
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for (i = 0; i < ARRAY_SIZE(probe_array); i++)
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marker_probe_unregister(probe_array[i].name,
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probe_array[i].probe_func, &probe_array[i]);
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printk(KERN_INFO "Number of event b : %u\n",
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atomic_read(&eventb_count));
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}
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module_init(probe_init);
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module_exit(probe_fini);
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MODULE_LICENSE("GPL");
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MODULE_AUTHOR("Mathieu Desnoyers");
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MODULE_DESCRIPTION("SUBSYSTEM Probe");
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