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>
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Mathieu Desnoyers
committed by
Linus Torvalds
Linus Torvalds
parent
9170d2f6e1
commit
fb40bd78b0
@ -19,16 +19,23 @@ struct marker;
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/**
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* marker_probe_func - Type of a marker probe function
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* @mdata: pointer of type struct marker
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* @private_data: caller site private data
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* @probe_private: probe private data
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* @call_private: call site private data
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* @fmt: format string
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* @...: variable argument list
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* @args: variable argument list pointer. Use a pointer to overcome C's
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* inability to pass this around as a pointer in a portable manner in
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* the callee otherwise.
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*
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* Type of marker probe functions. They receive the mdata and need to parse the
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* format string to recover the variable argument list.
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*/
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typedef void marker_probe_func(const struct marker *mdata,
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void *private_data, const char *fmt, ...);
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typedef void marker_probe_func(void *probe_private, void *call_private,
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const char *fmt, va_list *args);
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struct marker_probe_closure {
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marker_probe_func *func; /* Callback */
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void *probe_private; /* Private probe data */
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};
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struct marker {
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const char *name; /* Marker name */
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@ -36,8 +43,11 @@ struct marker {
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* variable argument list.
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*/
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char state; /* Marker state. */
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marker_probe_func *call;/* Probe handler function pointer */
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void *private; /* Private probe data */
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char ptype; /* probe type : 0 : single, 1 : multi */
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void (*call)(const struct marker *mdata, /* Probe wrapper */
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void *call_private, const char *fmt, ...);
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struct marker_probe_closure single;
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struct marker_probe_closure *multi;
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} __attribute__((aligned(8)));
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#ifdef CONFIG_MARKERS
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@ -49,7 +59,7 @@ struct marker {
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* not add unwanted padding between the beginning of the section and the
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* structure. Force alignment to the same alignment as the section start.
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*/
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#define __trace_mark(name, call_data, format, args...) \
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#define __trace_mark(name, call_private, format, args...) \
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do { \
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static const char __mstrtab_name_##name[] \
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__attribute__((section("__markers_strings"))) \
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@ -60,24 +70,23 @@ struct marker {
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static struct marker __mark_##name \
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__attribute__((section("__markers"), aligned(8))) = \
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{ __mstrtab_name_##name, __mstrtab_format_##name, \
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0, __mark_empty_function, NULL }; \
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0, 0, marker_probe_cb, \
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{ __mark_empty_function, NULL}, NULL }; \
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__mark_check_format(format, ## args); \
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if (unlikely(__mark_##name.state)) { \
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preempt_disable(); \
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(*__mark_##name.call) \
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(&__mark_##name, call_data, \
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(&__mark_##name, call_private, \
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format, ## args); \
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preempt_enable(); \
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} \
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} while (0)
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extern void marker_update_probe_range(struct marker *begin,
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struct marker *end, struct module *probe_module, int *refcount);
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struct marker *end);
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#else /* !CONFIG_MARKERS */
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#define __trace_mark(name, call_data, format, args...) \
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#define __trace_mark(name, call_private, format, args...) \
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__mark_check_format(format, ## args)
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static inline void marker_update_probe_range(struct marker *begin,
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struct marker *end, struct module *probe_module, int *refcount)
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struct marker *end)
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{ }
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#endif /* CONFIG_MARKERS */
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@ -92,8 +101,6 @@ static inline void marker_update_probe_range(struct marker *begin,
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#define trace_mark(name, format, args...) \
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__trace_mark(name, NULL, format, ## args)
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#define MARK_MAX_FORMAT_LEN 1024
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/**
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* MARK_NOARGS - Format string for a marker with no argument.
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*/
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@ -106,24 +113,30 @@ static inline void __printf(1, 2) __mark_check_format(const char *fmt, ...)
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extern marker_probe_func __mark_empty_function;
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extern void marker_probe_cb(const struct marker *mdata,
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void *call_private, const char *fmt, ...);
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extern void marker_probe_cb_noarg(const struct marker *mdata,
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void *call_private, const char *fmt, ...);
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/*
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* Connect a probe to a marker.
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* private data pointer must be a valid allocated memory address, or NULL.
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*/
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extern int marker_probe_register(const char *name, const char *format,
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marker_probe_func *probe, void *private);
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marker_probe_func *probe, void *probe_private);
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/*
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* Returns the private data given to marker_probe_register.
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*/
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extern void *marker_probe_unregister(const char *name);
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extern int marker_probe_unregister(const char *name,
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marker_probe_func *probe, void *probe_private);
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/*
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* Unregister a marker by providing the registered private data.
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*/
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extern void *marker_probe_unregister_private_data(void *private);
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extern int marker_probe_unregister_private_data(marker_probe_func *probe,
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void *probe_private);
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extern int marker_arm(const char *name);
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extern int marker_disarm(const char *name);
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extern void *marker_get_private_data(const char *name);
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extern void *marker_get_private_data(const char *name, marker_probe_func *probe,
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int num);
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#endif
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