Hi Sebastian,
> > > > > > The kernel version 4.1.37-rt43 is working fine, the kernel
> > > > > > versions
> > > > > > 4.4.39-rt50 and
> > > > > 4.8.11-rt7 show the same strange behavior as 4.9.0-rt1.
> > > > > > Something on the way between 4.1.37-rt43 and 4.4.39-rt50 seems
> > > > > > to cause the
> > > > > trouble.
> > > > >
> > > > > can you check if one of the earlier v4.4-RT releases (maybe
> > > > > start with
> > > > > -rt2 or -rt1) also shows this behaviour?
> > > > > If not, would you have a testcase?
> > > > I tested with 4.4.0-rt2.
> > > > Here this issue occurs very rarely. I ran the gdb for about 30
> > > > times, and here I got one hit.
> > > > With the other kernel versions I got the issue in 20-40% of the cases.
> > > >
> > > > I will try out the other 4.4.0 releases...
> > >
> > > I ran more tests. The kernel 4.4.1-rt4 is working fairly fine (only
> > > about one hit every 30 runs) but the kernel 4.4.1-rt5 is causing the
> > > issue very
> > often.
> >
> > and 4.1.37-rt43 shows not SIGSTOPS in 100 runs?
> That's right.
> I used 4.1.37-rt43 and ran the test for 200 times. There was no single issue.
I have now a simple executable where I can reproduce a very similar issue.
It might be related to the one I see as it effects also gdb debugging.
The simple executable (see below or in the attachment) runs perfectly without gdb.
However, using kernel version 4.4.1-rt6 and also with 4.9.4-rt2 it very often does not run properly
using gdb.
In kernel version 4.1.37-rt43 it always runs properly in gdb.
Whenever the issue occurs, the gdb does not reach the end of the executable.
I have to stop the gdb with with CTRL-C.
Here is the gdb output of kernel 4.9.4-rt7
(gdb) info thr
shows
Id Target Id Frame
* 1 Thread 0x7ffff7fdf700 (LWP 5383) "gdb-issue" 0x00007ffff79bd6bd in pthread_join (threadid=140737343743744,
thread_return=0x0) at pthread_join.c:90
2 Thread 0x7ffff7616700 (LWP 5387) "gdb-issue" 0x00007ffff76cee4b in __GI___waitpid (pid=5540,
stat_loc=stat_loc@entry=0x7ffff7615d50, options=options@entry=0) at ../sysdeps/unix/sysv/linux/waitpid.c:29
(gdb) thr 2
(gdb) bt
shows
#0 0x00007ffff76cee4b in __GI___waitpid (pid=5540, stat_loc=stat_loc@entry=0x7ffff7615d50, options=options@entry=0)
at ../sysdeps/unix/sysv/linux/waitpid.c:29
#1 0x00007ffff765608b in do_system (line=<optimized out>) at ../sysdeps/posix/system.c:148
#2 0x0000555555554df8 in thread_func (arg=0x5555557560c0 <thread_data>) at gdb-issue.c:54
#3 0x00007ffff79bc464 in start_thread (arg=0x7ffff7616700) at pthread_create.c:333
#4 0x00007ffff76ff9df in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:105
Sometimes it works fine, however in about 20-30% of the runs, the gdb session does not work properly.
Does this give you any hint?
Thanks for the support.
Regards
Mathias
--------------- BEGIN of C CODE -------------
#define _GNU_SOURCE
#include <sched.h>
#include <stdio.h>
#include <string.h>
#include <pthread.h>
#include <stdint.h>
#include <stdlib.h>
#include <unistd.h>
#include <stdbool.h>
#include <sys/eventfd.h>
#include <sys/mman.h>
static volatile bool terminated;
typedef struct
{
pthread_t thread;
int id;
int trigger_fd;
}
thread_data_t;
void *thread_func(void *arg)
{
int rc;
thread_data_t *thr = arg;
int loop;
{
struct sched_param param;
memset(¶m, 0, sizeof(param));
param.sched_priority = 60;
rc = pthread_setschedparam(pthread_self(), SCHED_FIFO, ¶m);
if (rc) {
fprintf(stderr, "pthread_setschedparam %m\n");
exit(1);
}
/* Run each thread on a separate CPU core */
cpu_set_t set;
CPU_ZERO(&set);
CPU_SET(thr->id, &set);
rc = sched_setaffinity(0, sizeof(set), &set);
if (rc) {
fprintf(stderr, "sched_setaffinity %m\n");
exit(1);
}
}
for (loop=0; !terminated ; loop++) {
uint64_t u64;
int rc = read(thr->trigger_fd, &u64, 8);
if (rc > 0) {
/* printf("thread %i loop %i\n", thr->id, loop); */
system("lspci -xxx > /dev/null");
}
else {
fprintf(stderr, "read %m\n");
}
}
printf("End of thread %i\n", thr->id);
return NULL;
}
#define NO_THREADS 4
static thread_data_t thread_data[NO_THREADS];
int main(int argc, char *argv[])
{
int i;
int rc;
/* Init */
mlockall(MCL_CURRENT | MCL_FUTURE);
for (i=0; i<NO_THREADS; i++) {
thread_data[i].id = i;
rc = thread_data[i].trigger_fd = eventfd(0,0);
if (rc < 0) {
fprintf(stderr, "Error creating eventfd: %m\n");
return 1;
}
}
for (i=0; i<NO_THREADS; i++) {
rc = pthread_create(&thread_data[i].thread, NULL, thread_func, &thread_data[i]);
if (rc) {
fprintf(stderr, "Error creating thread: %m\n");
return 1;
}
}
/* Loop */
int j;
int max = 100;
for (j=0; j<=max; j++) {
struct timespec ts = { 0, 10000000 };
clock_nanosleep(CLOCK_MONOTONIC, 0, &ts, NULL);
if (j == max) {
terminated = true;
}
for (i=0; i<NO_THREADS; i++) {
uint64_t u64 = 1;
write(thread_data[i].trigger_fd, &u64, 8);
}
}
/* Cleanup */
for (i=0; i<NO_THREADS; i++) {
pthread_join(thread_data[i].thread, NULL);
printf("Thread %i joined\n", i);
close(thread_data[i].trigger_fd);
}
return 0;
}
--------------- END of C CODE -------------
Attachment:
gdb-issue.tgz
Description: gdb-issue.tgz
