Commit fb40bd78 authored by Mathieu Desnoyers's avatar Mathieu Desnoyers Committed by Linus Torvalds
Browse files

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: default avatarMathieu 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: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 9170d2f6

arch/powerpc/platforms/cell/spufs/sputrace.c

+11 −20
Original line number Diff line number Diff line
@@ -146,34 +146,28 @@ static void sputrace_log_item(const char *name, struct spu_context *ctx, 
	wake_up(&sputrace_wait);

}



static void spu_context_event(const struct marker *mdata,

		void *private, const char *format, ...)

static void spu_context_event(void *probe_private, void *call_data,

		const char *format, va_list *args)

{

	struct spu_probe *p = mdata->private;

	va_list ap;

	struct spu_probe *p = probe_private;

	struct spu_context *ctx;

	struct spu *spu;



	va_start(ap, format);

	ctx = va_arg(ap, struct spu_context *);

	spu = va_arg(ap, struct spu *);

	ctx = va_arg(*args, struct spu_context *);

	spu = va_arg(*args, struct spu *);



	sputrace_log_item(p->name, ctx, spu);

	va_end(ap);

}



static void spu_context_nospu_event(const struct marker *mdata,

		void *private, const char *format, ...)

static void spu_context_nospu_event(void *probe_private, void *call_data,

		const char *format, va_list *args)

{

	struct spu_probe *p = mdata->private;

	va_list ap;

	struct spu_probe *p = probe_private;

	struct spu_context *ctx;



	va_start(ap, format);

	ctx = va_arg(ap, struct spu_context *);

	ctx = va_arg(*args, struct spu_context *);



	sputrace_log_item(p->name, ctx, NULL);

	va_end(ap);

}



struct spu_probe spu_probes[] = {
@@ -219,10 +213,6 @@ static int __init sputrace_init(void) 
		if (error)

			printk(KERN_INFO "Unable to register probe %s\n",

					p->name);



		error = marker_arm(p->name);

		if (error)

			printk(KERN_INFO "Unable to arm probe %s\n", p->name);

	}



	return 0;
@@ -238,7 +228,8 @@ static void __exit sputrace_exit(void) 
	int i;



	for (i = 0; i < ARRAY_SIZE(spu_probes); i++)

		marker_probe_unregister(spu_probes[i].name);

		marker_probe_unregister(spu_probes[i].name,

			spu_probes[i].probe_func, &spu_probes[i]);



	remove_proc_entry("sputrace", NULL);

	kfree(sputrace_log);

include/linux/marker.h

+36 −23
Original line number Diff line number Diff line
@@ -19,16 +19,23 @@ struct marker; 


/**

 * marker_probe_func - Type of a marker probe function

 * @mdata: pointer of type struct marker

 * @private_data: caller site private data

 * @probe_private: probe private data

 * @call_private: call site private data

 * @fmt: format string

 * @...: variable argument list

 * @args: variable argument list pointer. Use a pointer to overcome C's

 *        inability to pass this around as a pointer in a portable manner in

 *        the callee otherwise.

 *

 * Type of marker probe functions. They receive the mdata and need to parse the

 * format string to recover the variable argument list.

 */

typedef void marker_probe_func(const struct marker *mdata,

	void *private_data, const char *fmt, ...);

typedef void marker_probe_func(void *probe_private, void *call_private,

		const char *fmt, va_list *args);



struct marker_probe_closure {

	marker_probe_func *func;	/* Callback */

	void *probe_private;		/* Private probe data */

};



struct marker {

	const char *name;	/* Marker name */
@@ -36,8 +43,11 @@ struct marker { 
				 * variable argument list.

				 */

	char state;		/* Marker state. */

	marker_probe_func *call;/* Probe handler function pointer */

	void *private;		/* Private probe data */

	char ptype;		/* probe type : 0 : single, 1 : multi */

	void (*call)(const struct marker *mdata,	/* Probe wrapper */

		void *call_private, const char *fmt, ...);

	struct marker_probe_closure single;

	struct marker_probe_closure *multi;

} __attribute__((aligned(8)));



#ifdef CONFIG_MARKERS
@@ -49,7 +59,7 @@ struct marker { 
 * not add unwanted padding between the beginning of the section and the

 * structure. Force alignment to the same alignment as the section start.

 */

#define __trace_mark(name, call_data, format, args...)			\

#define __trace_mark(name, call_private, format, args...)		\

	do {								\

		static const char __mstrtab_name_##name[]		\

		__attribute__((section("__markers_strings")))		\
@@ -60,24 +70,23 @@ struct marker { 
		static struct marker __mark_##name			\

		__attribute__((section("__markers"), aligned(8))) =	\

		{ __mstrtab_name_##name, __mstrtab_format_##name,	\

		0, __mark_empty_function, NULL };			\

		0, 0, marker_probe_cb,					\

		{ __mark_empty_function, NULL}, NULL };			\

		__mark_check_format(format, ## args);			\

		if (unlikely(__mark_##name.state)) {			\

			preempt_disable();				\

			(*__mark_##name.call)				\

				(&__mark_##name, call_data,		\

				(&__mark_##name, call_private,		\

				format, ## args);			\

			preempt_enable();				\

		}							\

	} while (0)



extern void marker_update_probe_range(struct marker *begin,

	struct marker *end, struct module *probe_module, int *refcount);

	struct marker *end);

#else /* !CONFIG_MARKERS */

#define __trace_mark(name, call_data, format, args...) \

#define __trace_mark(name, call_private, format, args...) \

		__mark_check_format(format, ## args)

static inline void marker_update_probe_range(struct marker *begin,

	struct marker *end, struct module *probe_module, int *refcount)

	struct marker *end)

{ }

#endif /* CONFIG_MARKERS */
@@ -92,8 +101,6 @@ static inline void marker_update_probe_range(struct marker *begin, 
#define trace_mark(name, format, args...) \

	__trace_mark(name, NULL, format, ## args)



#define MARK_MAX_FORMAT_LEN	1024



/**

 * MARK_NOARGS - Format string for a marker with no argument.

 */
@@ -106,24 +113,30 @@ static inline void __printf(1, 2) __mark_check_format(const char *fmt, ...) 


extern marker_probe_func __mark_empty_function;



extern void marker_probe_cb(const struct marker *mdata,

	void *call_private, const char *fmt, ...);

extern void marker_probe_cb_noarg(const struct marker *mdata,

	void *call_private, const char *fmt, ...);



/*

 * Connect a probe to a marker.

 * private data pointer must be a valid allocated memory address, or NULL.

 */

extern int marker_probe_register(const char *name, const char *format,

				marker_probe_func *probe, void *private);

				marker_probe_func *probe, void *probe_private);



/*

 * Returns the private data given to marker_probe_register.

 */

extern void *marker_probe_unregister(const char *name);

extern int marker_probe_unregister(const char *name,

	marker_probe_func *probe, void *probe_private);

/*

 * Unregister a marker by providing the registered private data.

 */

extern void *marker_probe_unregister_private_data(void *private);

extern int marker_probe_unregister_private_data(marker_probe_func *probe,

	void *probe_private);



extern int marker_arm(const char *name);

extern int marker_disarm(const char *name);

extern void *marker_get_private_data(const char *name);

extern void *marker_get_private_data(const char *name, marker_probe_func *probe,

	int num);



#endif

include/linux/module.h

+1 −1
Original line number Diff line number Diff line
@@ -465,7 +465,7 @@ int unregister_module_notifier(struct notifier_block * nb); 


extern void print_modules(void);



extern void module_update_markers(struct module *probe_module, int *refcount);

extern void module_update_markers(void);



#else /* !CONFIG_MODULES... */

#define EXPORT_SYMBOL(sym)

kernel/marker.c

+505 −172

File changed.

Preview size limit exceeded, changes collapsed.

kernel/module.c

+3 −4
Original line number Diff line number Diff line
@@ -2038,7 +2038,7 @@ static struct module *load_module(void __user *umod, 
#ifdef CONFIG_MARKERS

	if (!mod->taints)

		marker_update_probe_range(mod->markers,

			mod->markers + mod->num_markers, NULL, NULL);

			mod->markers + mod->num_markers);

#endif

	err = module_finalize(hdr, sechdrs, mod);

	if (err < 0)
@@ -2564,7 +2564,7 @@ EXPORT_SYMBOL(struct_module); 
#endif



#ifdef CONFIG_MARKERS

void module_update_markers(struct module *probe_module, int *refcount)

void module_update_markers(void)

{

	struct module *mod;
@@ -2572,8 +2572,7 @@ void module_update_markers(struct module *probe_module, int *refcount) 
	list_for_each_entry(mod, &modules, list)

		if (!mod->taints)

			marker_update_probe_range(mod->markers,

				mod->markers + mod->num_markers,

				probe_module, refcount);

				mod->markers + mod->num_markers);

	mutex_unlock(&module_mutex);

}

#endif

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