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 --- include/linux/marker.h | 59 ++++++++++++++++++++++++++++++-------------------- 1 file changed, 36 insertions(+), 23 deletions(-) (limited to 'include/linux/marker.h') diff --git a/include/linux/marker.h b/include/linux/marker.h index 5f36cf946bc..b5f95637f28 100644 --- a/include/linux/marker.h +++ b/include/linux/marker.h @@ -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 -- cgit v1.2.3 From b2e3e658b344c6bcfb8fb694100ab2f2b5b2edb0 Mon Sep 17 00:00:00 2001 From: Mathieu Desnoyers Date: Wed, 13 Feb 2008 15:03:39 -0800 Subject: Linux Kernel Markers: create modpost file This adds some new magic in the MODPOST phase for CONFIG_MARKERS. Analogous to the Module.symvers file, the build will now write a Module.markers file when CONFIG_MARKERS=y is set. This file lists the name, defining module, and format string of each marker, separated by \t characters. This simple text file can be used by offline build procedures for instrumentation code, analogous to how System.map and Module.symvers can be useful to have for kernels other than the one you are running right now. The strings are made easy to extract by having the __trace_mark macro define the name and format together in a single array called __mstrtab_* in the __markers_strings section. This is straightforward and reliable as long as the marker structs are always defined by this macro. It is an unreasonable amount of hairy work to extract the string pointers from the __markers section structs, which entails handling a relocation type for every machine under the sun. Mathieu : - Ran through checkpatch.pl Signed-off-by: Roland McGrath Signed-off-by: Mathieu Desnoyers Cc: David Smith Cc: Sam Ravnborg Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/marker.h | 9 +++------ 1 file changed, 3 insertions(+), 6 deletions(-) (limited to 'include/linux/marker.h') diff --git a/include/linux/marker.h b/include/linux/marker.h index b5f95637f28..5df879dc377 100644 --- a/include/linux/marker.h +++ b/include/linux/marker.h @@ -61,15 +61,12 @@ struct marker { */ #define __trace_mark(name, call_private, format, args...) \ do { \ - static const char __mstrtab_name_##name[] \ + static const char __mstrtab_##name[] \ __attribute__((section("__markers_strings"))) \ - = #name; \ - static const char __mstrtab_format_##name[] \ - __attribute__((section("__markers_strings"))) \ - = format; \ + = #name "\0" format; \ static struct marker __mark_##name \ __attribute__((section("__markers"), aligned(8))) = \ - { __mstrtab_name_##name, __mstrtab_format_##name, \ + { __mstrtab_##name, &__mstrtab_##name[sizeof(#name)], \ 0, 0, marker_probe_cb, \ { __mark_empty_function, NULL}, NULL }; \ __mark_check_format(format, ## args); \ -- cgit v1.2.3