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dtracy: make timer probes run in interrupt context

When probing a timer, we were running in our own kproc,
and not in an interrupt context, which meant that we didn't
have any access to anything worth sampling, so we didn't
give any data back.

This moves the probe to the hzclock interrupt, and returns
the pc in the probe.

--- a/sys/src/9/port/dtracytimer.c

+++ b/sys/src/9/port/dtracytimer.c

@@ -4,38 +4,37 @@

 #include	"dat.h"

 #include	"fns.h"

 #include	"../port/error.h"

+#include	"ureg.h"

 #include	<dtracy.h>

 static DTProbe *timerprobe;

+static int	running;

-static void

-dtracytimer(void *)

+void

+dtracytick(Ureg *ur)

 {

 	DTTrigInfo info;

+	if(!running)

+		return;

 	memset(&info, 0, sizeof(info));

-	for(;;){

-		tsleep(&up->sleep, return0, nil, 1000);

-		dtptrigger(timerprobe, &info);

-	}

+	info.arg[0] = ur->pc;

+	info.arg[1] = userureg(ur);

+	dtptrigger(timerprobe, &info);

 }

 static void

 timerprovide(DTProvider *prov)

 {

-	timerprobe = dtpnew("timer::1s", prov, nil);

+	if(timerprobe == nil)

+		timerprobe = dtpnew("timer::1tk", prov, nil);

 }

 static int

 timerenable(DTProbe *)

 {

-	static int gotkproc;

-	

-	if(!gotkproc){

-		kproc("dtracytimer", dtracytimer, nil);

-		gotkproc=1;

-	}

+	running = 1;

 	return 0;

 }

@@ -42,6 +41,7 @@

 static void

 timerdisable(DTProbe *)

 {

+	running = 0;

 }

 DTProvider dtracytimerprov = {

--- a/sys/src/9/port/portclock.c

+++ b/sys/src/9/port/portclock.c

@@ -154,6 +154,7 @@

 	}

 	accounttime();

+	dtracytick(ur);

 	kmapinval();

 	if(kproftimer != nil)

--- a/sys/src/9/port/portfns.h

+++ b/sys/src/9/port/portfns.h

@@ -82,6 +82,7 @@

 Dir*		dirchanstat(Chan *);

 void		drawactive(int);

 void		drawcmap(void);

+void		dtracytick(Ureg*);

 void		dumpaproc(Proc*);

 void		dumpregs(Ureg*);

 void		dumpstack(void);