Messages in this thread |  | | Date | Tue, 2 Oct 2001 10:31:12 +0200 | From | Balazs Scheidler <> | Subject | Re: reproducible bug in 2.2.19 & 2.4.x |
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On Fri, Sep 28, 2001 at 01:01:38PM +0200, Balazs Scheidler wrote: > I added a backtrace function to my test program to show where it > aborts, and here's the result: > > Signal (11) received, stackdump follows; eax='ffffffe0', ebx='0000000c', ecx='be5ff96c', edx='00000400', eip='00000001' > retaddr=0x1, ebp=0xbe5ff944 > retaddr=0x804892a, ebp=0xbe5ffd74 > retaddr=0x4001bc9f, ebp=0xbe5ffe34 > > The program _always_ aborted at eip=0x1. > > the program didn't abort if I removed the syslog() function call from the > thread.
I received an idea, suggesting that syslog() is not reentrant and this causes problems.
I added mutexes around my syslog call and the problem still occurs, although slower.
I'm trying to remove syslog() and add some sigaction calls instead (which I think is the culprit) I attach my modified stressthreads.c
-- 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
pthread_mutex_t syslog_mutex = PTHREAD_MUTEX_INITIALIZER;
void *thread_func(void *arg) { int fd = *(int *) arg; int i; char buf[1024];
pthread_mutex_lock(&syslog_mutex); syslog(LOG_DEBUG, "thread started...%p\n", pthread_self()); pthread_mutex_unlock(&syslog_mutex); 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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