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SubjectRe: reproducible bug in 2.2.19 & 2.4.x
On Fri, Sep 28, 2001 at 03:15:32PM -0400, Mark Hahn wrote:
>
> seems like an interaction between your signal code and pthread,
> no obvious reason to blame the kernel:

I've updated my test program to address your issues:

1) I removed the SIGSEGV handler (you know with the fprintf())
2) I modified it to use separate memory for all thread initialization data

The segfault still occurs. (to reenable backtrace #define BACKTRACE to 1 at
the beginning of the program) core is not dumped, because threaded programs
do not drop core.

I still think it's a kernel issue, at least the SMP dependancy tells me so.
(remember SMP kernel on an UP is affected too)

I also attach the strace of the process, which also shows the segfault. (it
is made by strace 4.4 which can follow threads)

PS: again please Cc me, since I'm not subscribed.

--
Bazsi
PGP info: KeyID 9AF8D0A9 Fingerprint CD27 CFB0 802C 0944 9CFD 804E C82C 8EB1
#include <pthread.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <signal.h>
#include <syslog.h>
#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>

#define BACKTRACE 0


#if BACKTRACE
void inline
z_dump_backtrace(unsigned long eip, unsigned long first_ebp)
{
/* NOTE: this is i386 specific */
unsigned long *ebp;

fprintf(stderr, "retaddr=0x%lx, ebp=0x%lx\n", eip, first_ebp);

ebp = (unsigned long *) first_ebp;
while (ebp > (unsigned long *) &ebp && *ebp)
{
fprintf(stderr, "retaddr=0x%lx, ebp=0x%lx\n", *(ebp+1), *ebp);
ebp = (unsigned long *) *ebp;
}
}

void
z_fatal_signal_handler(int signo)
{
struct sigcontext *p = (struct sigcontext *) (((char *) &p) + 16);

fprintf(stderr, "Signal (%d) received, stackdump follows; eax='%08lx', ebx='%08lx', ecx='%08lx', edx='%08lx', eip='%08lx'\n",
signo, p->eax, p->ebx, p->ecx, p->edx, p->eip);
z_dump_backtrace(p->eip, p->ebp);
exit(1);
}
#endif

void *thread_func(void *arg)
{
int fd = *(int *) arg;
int i;
char buf[1024];

syslog(LOG_DEBUG, "thread started...%p\n", pthread_self());
memset(buf, 'a', sizeof(buf));
for (i = 0; i < 1024; i++)
{
write(fd, buf, sizeof(buf));
}
close(fd);
//syslog(LOG_DEBUG, "thread stopped...%p\n", pthread_self());
free(arg);
return NULL;
}

int main()
{
int fd;
struct sockaddr_in sin;
int tmp = 1;

#if BACKTRACE
signal(SIGSEGV, z_fatal_signal_handler);
#endif
signal(SIGPIPE, SIG_IGN);

fd = socket(AF_INET, SOCK_STREAM, 0);

sin.sin_family = AF_INET;
sin.sin_port = htons(10000);
sin.sin_addr.s_addr = INADDR_ANY;

setsockopt(fd, SOL_SOCKET, SO_REUSEADDR, &tmp, sizeof(tmp));

if (bind(fd, (struct sockaddr *) &sin, sizeof(sin)) < 0)
{
perror("bind");
return 0;
}

listen(fd, 255);

while (1)
{
int newfd;
int tmplen;
pthread_t t;

tmplen = sizeof(sin);
newfd = accept(fd, (struct sockaddr *) &sin, &tmplen);
if (newfd == -1)
{
perror("accept");
}
else
{
int *state = (int *) malloc(sizeof(int));

*state = newfd;
pthread_create(&t, NULL, thread_func, state);
}
}
}
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