/* $Id: signal.c,v 1.20 2005/04/08 14:37:55 mikpe Exp $
*
* This test program illustrates how performance counter overflow
* can be caught and sent to the process as a user-specified signal.
*
* Limitations:
* - Requires a 2.4 or newer kernel with local APIC support.
* - Requires a CPU with a local APIC (P4, P6, K8, K7).
*
* Copyright (C) 2001-2004 Mikael Pettersson
*/
#define __USE_GNU /* enable symbolic names for gregset_t[] indices */
#include <sys/ucontext.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "libperfctr.h"
#include "arch.h"
static struct vperfctr *vperfctr;
static struct perfctr_info info;
static void do_open(void)
{
vperfctr = vperfctr_open();
if( !vperfctr ) {
perror("vperfctr_open");
exit(1);
}
if( vperfctr_info(vperfctr, &info) < 0 ) {
perror("vperfctr_info");
exit(1);
}
if( !(info.cpu_features & PERFCTR_FEATURE_PCINT) )
printf("PCINT not supported -- expect failure\n");
}
static void on_sigio(int sig, siginfo_t *si, void *puc)
{
struct ucontext *uc;
unsigned long pc;
unsigned int pmc_mask;
if( sig != SIGIO ) {
printf("%s: unexpected signal %d\n", __FUNCTION__, sig);
return;
}
if( si->si_code != SI_PMC_OVF ) {
printf("%s: unexpected si_code #%x\n", __FUNCTION__, si->si_code);
return;
}
if( (pmc_mask = si->si_pmc_ovf_mask) == 0 ) {
printf("%s: overflow PMCs not identified\n", __FUNCTION__);
return;
}
uc = puc;
pc = ucontext_pc(uc);
if( !vperfctr_is_running(vperfctr) ) {
/*
* My theory is that this happens if a perfctr overflowed
* at the very instruction for the VPERFCTR_STOP call.
* Signal delivery is delayed until the kernel returns to
* user-space, at which time VPERFCTR_STOP will already
* have marked the vperfctr as stopped. In this case, we
* cannot and must not attempt to IRESUME it.
* This can be triggered by counting e.g. BRANCHES and setting
* the overflow limit ridiculously low.
*/
printf("%s: unexpected overflow from PMC set %#x at pc %#lx\n",
__FUNCTION__, pmc_mask, pc);
return;
}
printf("%s: PMC overflow set %#x at pc %#lx\n", __FUNCTION__, pmc_mask, pc);
if( vperfctr_iresume(vperfctr) < 0 ) {
perror("vperfctr_iresume");
abort();
}
}
static void do_sigaction(void)
{
struct sigaction sa;
memset(&sa, 0, sizeof sa);
sa.sa_sigaction = on_sigio;
sa.sa_flags = SA_SIGINFO;
if( sigaction(SIGIO, &sa, NULL) < 0 ) {
perror("sigaction");
exit(1);
}
}
static void do_control(void)
{
struct vperfctr_control control;
memset(&control, 0, sizeof control);
do_setup(&info, &control.cpu_control);
control.si_signo = SIGIO;
printf("Control used:\n");
perfctr_cpu_control_print(&control.cpu_control);
printf("\n");
if( vperfctr_control(vperfctr, &control) < 0 ) {
perror("vperfctr_control");
exit(1);
}
}
static void do_stop(void)
{
struct sigaction sa;
if( vperfctr_stop(vperfctr) )
perror("vperfctr_stop");
memset(&sa, 0, sizeof sa);
sa.sa_handler = SIG_DFL;
if( sigaction(SIGIO, &sa, NULL) < 0 ) {
perror("sigaction");
exit(1);
}
}
#define N 150
static double v[N], w[N];
static double it;
static void do_dotprod(void)
{
int i;
double sum;
sum = 0.0;
for(i = 0; i < N; ++i)
sum += v[i] * w[i];
it = sum;
}
int main(void)
{
do_sigaction();
do_open();
do_control();
do_dotprod();
do_stop();
return 0;
}