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SubjectRe: perf/tracepoint: another fuzzer generated lockup
On Fri, 8 Nov 2013, Frederic Weisbecker wrote:

> On Fri, Nov 08, 2013 at 03:23:07PM -0500, Vince Weaver wrote:
> > On Fri, 8 Nov 2013, Frederic Weisbecker wrote:
> > >
> > > There seem to be a loop that takes too long in intel_pmu_handle_irq(). Your two
> > > previous reports seemed to suggest that lbr is involved, but not this one.
> >
> > I may be wrong but I think everything between <NMI> and <EOE> is just
> > noise from the NMI perf-event watchdog timer kicking in.
>
> Ah good point.
>
> So the pattern seem to be that irq work/perf_event_wakeup is involved, may be
> interrupting a tracepoint event or so.

I managed to construct a reproducible test case, which is attached. I
sometimes have to run it 5-10 times before it triggers.

> It would be nice if you enable CONFIG_FRAME_POINTER in your future reports
> so that we get more precise traces. Or may be you actually enabled it and it
> doesn't work?

No, it's not enabled, I can try setting that in the future.

Vince


/* log_to_code output from ./new.trace */
/* by Vince Weaver <vincent.weaver _at_ maine.edu */

#define _GNU_SOURCE 1
#include <stdio.h>
#include <unistd.h>
#include <fcntl.h>
#include <string.h>
#include <signal.h>
#include <sys/mman.h>
#include <sys/syscall.h>
#include <sys/ioctl.h>
#include <sys/prctl.h>
#include <poll.h>
#include <linux/hw_breakpoint.h>
#include <linux/perf_event.h>

int fd[1024];
struct perf_event_attr pe[1024];
char *mmap_result[1024];
#define MAX_READ_SIZE 65536
static long long data[MAX_READ_SIZE];

#define MAX_POLL_FDS 128
struct pollfd pollfds[MAX_POLL_FDS];

long long id;

int forked_pid;

struct sigaction sa;
static int overflows=0;
static int sigios=0;

static void our_handler(int signum, siginfo_t *info, void *uc) {
int fd = info->si_fd;
int ret;

overflows++;
ioctl(fd,PERF_EVENT_IOC_DISABLE,0);
if (sigios) return;
ret=ioctl(fd, PERF_EVENT_IOC_REFRESH,1);
}
int perf_event_open(struct perf_event_attr *hw_event_uptr,
pid_t pid, int cpu, int group_fd, unsigned long flags) {

return syscall(__NR_perf_event_open,hw_event_uptr, pid, cpu,
group_fd, flags);
}

int main(int argc, char **argv) {
/* 1 */
/* fd = 82 */

memset(&pe[82],0,sizeof(struct perf_event_attr));
pe[82].type=PERF_TYPE_TRACEPOINT;
pe[82].size=80;
pe[82].config=0x18;
pe[82].sample_period=0xdd95cac7b947b610;
pe[82].sample_type=PERF_SAMPLE_IP|PERF_SAMPLE_TIME|PERF_SAMPLE_READ|PERF_SAMPLE_CALLCHAIN|PERF_SAMPLE_PERIOD|PERF_SAMPLE_DATA_SRC;
//|PERF_SAMPLE_IDENTIFIER; /* 18135 */
pe[82].read_format=PERF_FORMAT_TOTAL_TIME_ENABLED|PERF_FORMAT_TOTAL_TIME_RUNNING|PERF_FORMAT_ID|PERF_FORMAT_GROUP; /* f */
pe[82].exclude_hv=1;
pe[82].mmap=1;
pe[82].comm=1;
pe[82].watermark=1;
pe[82].precise_ip=1; /* constant skid */
pe[82].mmap_data=1;
pe[82].exclude_host=1;
pe[82].exclude_guest=1;
pe[82].exclude_callchain_user=1;
pe[82].wakeup_watermark=232;
pe[82].bp_type=HW_BREAKPOINT_EMPTY;
pe[82].config1=0x9;
pe[82].branch_sample_type=PERF_SAMPLE_BRANCH_USER|PERF_SAMPLE_BRANCH_KERNEL|PERF_SAMPLE_BRANCH_HV|PERF_SAMPLE_BRANCH_ANY|PERF_SAMPLE_BRANCH_ANY_CALL|PERF_SAMPLE_BRANCH_ANY_RETURN|PERF_SAMPLE_BRANCH_IND_CALL;
//|PERF_SAMPLE_BRANCH_ABORT_TX;
pe[82].sample_regs_user=39;
pe[82].sample_stack_user=37552;

fd[82]=perf_event_open(&pe[82],
0, /* current thread */
-1, /* all cpus */
-1, /* New Group Leader */
PERF_FLAG_FD_OUTPUT /*2*/ );


/* 2 */
mmap_result[82]=mmap(NULL, 20480,PROT_READ|PROT_WRITE, MAP_SHARED,fd[82], 0);
/* 3 */
memset(&sa, 0, sizeof(struct sigaction));
sa.sa_sigaction = our_handler;
sa.sa_flags = SA_SIGINFO;
if (sigaction( SIGRTMIN+2, &sa, NULL) < 0) {
printf("Error setting up signal handler\n");
}
fcntl(fd[82], F_SETFL, O_RDWR|O_NONBLOCK|O_ASYNC);
fcntl(fd[82], F_SETSIG, SIGRTMIN+2);
fcntl(fd[82], F_SETOWN,getpid());
/* Replayed 3 syscalls */
return 0;
}
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