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Commit dc102a8f authored by Mathieu Desnoyers's avatar Mathieu Desnoyers Committed by Thomas Gleixner
Browse files

Markers - remove extra format argument 



Denys Vlasenko <vda.linux@googlemail.com> :

> Not in this patch, but I noticed:
>
> #define __trace_mark(name, call_private, format, args...)               \
>         do {                                                            \
>                 static const char __mstrtab_##name[]                    \
>                 __attribute__((section("__markers_strings")))           \
>                 = #name "\0" format;                                    \
>                 static struct marker __mark_##name                      \
>                 __attribute__((section("__markers"), aligned(8))) =     \
>                 { __mstrtab_##name, &__mstrtab_##name[sizeof(#name)],   \
>                 0, 0, marker_probe_cb,                                  \
>                 { __mark_empty_function, NULL}, NULL };                 \
>                 __mark_check_format(format, ## args);                   \
>                 if (unlikely(__mark_##name.state)) {                    \
>                         (*__mark_##name.call)                           \
>                                 (&__mark_##name, call_private,          \
>                                 format, ## args);                       \
>                 }                                                       \
>         } while (0)
>
> In this call:
>
>                         (*__mark_##name.call)                           \
>                                 (&__mark_##name, call_private,          \
>                                 format, ## args);                       \
>
> you make gcc allocate duplicate format string. You can use
> &__mstrtab_##name[sizeof(#name)] instead since it holds the same string,
> or drop ", format," above and "const char *fmt" from here:
>
>         void (*call)(const struct marker *mdata,        /* Probe wrapper */
>                 void *call_private, const char *fmt, ...);
>
> since mdata->format is the same and all callees which need it can take it there.

Very good point. I actually thought about dropping it, since it would
remove an unnecessary argument from the stack. And actually, since I now
have the marker_probe_cb sitting between the marker site and the
callbacks, there is no API change required. Thanks :)

Mathieu

Signed-off-by: default avatarMathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
CC: Denys Vlasenko <vda.linux@googlemail.com>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
parent 3eefae99

include/linux/marker.h

+5 −6
Original line number Diff line number Diff line
@@ -44,8 +44,8 @@ struct marker { 
				 */

	char state;		/* Marker state. */

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

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

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

				/* Probe wrapper */

	void (*call)(const struct marker *mdata, void *call_private, ...);

	struct marker_probe_closure single;

	struct marker_probe_closure *multi;

} __attribute__((aligned(8)));
@@ -72,8 +72,7 @@ struct marker { 
		__mark_check_format(format, ## args);			\

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

			(*__mark_##name.call)				\

				(&__mark_##name, call_private,		\

				format, ## args);			\

				(&__mark_##name, call_private, ## args);\

		}							\

	} while (0)
@@ -117,9 +116,9 @@ 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, ...);

	void *call_private, ...);

extern void marker_probe_cb_noarg(const struct marker *mdata,

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

	void *call_private, ...);



/*

 * Connect a probe to a marker.

kernel/marker.c

+14 −16
Original line number Diff line number Diff line
@@ -55,8 +55,8 @@ static DEFINE_MUTEX(markers_mutex); 
struct marker_entry {

	struct hlist_node hlist;

	char *format;

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

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

			/* Probe wrapper */

	void (*call)(const struct marker *mdata, void *call_private, ...);

	struct marker_probe_closure single;

	struct marker_probe_closure *multi;

	int refcount;	/* Number of times armed. 0 if disarmed. */
@@ -91,15 +91,13 @@ EXPORT_SYMBOL_GPL(__mark_empty_function); 
 * marker_probe_cb Callback that prepares the variable argument list for probes.

 * @mdata: pointer of type struct marker

 * @call_private: caller site private data

 * @fmt: format string

 * @...:  Variable argument list.

 *

 * Since we do not use "typical" pointer based RCU in the 1 argument case, we

 * need to put a full smp_rmb() in this branch. This is why we do not use

 * rcu_dereference() for the pointer read.

 */

void marker_probe_cb(const struct marker *mdata, void *call_private,

	const char *fmt, ...)

void marker_probe_cb(const struct marker *mdata, void *call_private, ...)

{

	va_list args;

	char ptype;
@@ -120,8 +118,9 @@ void marker_probe_cb(const struct marker *mdata, void *call_private, 
		/* Must read the ptr before private data. They are not data

		 * dependant, so we put an explicit smp_rmb() here. */

		smp_rmb();

		va_start(args, fmt);

		func(mdata->single.probe_private, call_private, fmt, &args);

		va_start(args, call_private);

		func(mdata->single.probe_private, call_private, mdata->format,

			&args);

		va_end(args);

	} else {

		struct marker_probe_closure *multi;
@@ -136,9 +135,9 @@ void marker_probe_cb(const struct marker *mdata, void *call_private, 
		smp_read_barrier_depends();

		multi = mdata->multi;

		for (i = 0; multi[i].func; i++) {

			va_start(args, fmt);

			multi[i].func(multi[i].probe_private, call_private, fmt,

				&args);

			va_start(args, call_private);

			multi[i].func(multi[i].probe_private, call_private,

				mdata->format, &args);

			va_end(args);

		}

	}
@@ -150,13 +149,11 @@ EXPORT_SYMBOL_GPL(marker_probe_cb); 
 * marker_probe_cb Callback that does not prepare the variable argument list.

 * @mdata: pointer of type struct marker

 * @call_private: caller site private data

 * @fmt: format string

 * @...:  Variable argument list.

 *

 * Should be connected to markers "MARK_NOARGS".

 */

void marker_probe_cb_noarg(const struct marker *mdata,

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

void marker_probe_cb_noarg(const struct marker *mdata, void *call_private, ...)

{

	va_list args;	/* not initialized */

	char ptype;
@@ -172,7 +169,8 @@ void marker_probe_cb_noarg(const struct marker *mdata, 
		/* Must read the ptr before private data. They are not data

		 * dependant, so we put an explicit smp_rmb() here. */

		smp_rmb();

		func(mdata->single.probe_private, call_private, fmt, &args);

		func(mdata->single.probe_private, call_private, mdata->format,

			&args);

	} else {

		struct marker_probe_closure *multi;

		int i;
@@ -186,8 +184,8 @@ void marker_probe_cb_noarg(const struct marker *mdata, 
		smp_read_barrier_depends();

		multi = mdata->multi;

		for (i = 0; multi[i].func; i++)

			multi[i].func(multi[i].probe_private, call_private, fmt,

				&args);

			multi[i].func(multi[i].probe_private, call_private,

				mdata->format, &args);

	}

	preempt_enable();

}