On Thu, 2005-03-31 at 09:31 -0500, Jeff Bailey wrote:
> Miguel,
>
> I was looking through the sysklogd patch that you provided, and looked
> through the glibc code. I don't see any __libc_lock magic happening.
ctime() -> localtime() -> __tz_convert() -> __libc_lock_lock()
> Since ctime isn't reentrant, no effort is made to protect the coder
> against threaded programming. I also checked the 'time' function in
> case you were worried about that.
>
> Which glibc function were you worried about?
>
> I can see this code being included for completeness so that an entry
> isn't lost, but I don't think this is what's causing your breakage.
It is, I tested it :) Compile the attached C program, run with sarge
glibc on a 2.6 kernel. It's the most clear if you run it like this:
$ strace -e trace=\!time ./a.out
Lockup within a fraction of a second.
Mike.
#include <sys/time.h>
#include <time.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
volatile char *r;
void handler(int sig)
{
time_t t;
time(&t);
r = ctime(&t);
}
int main()
{
struct itimerval it;
struct sigaction sa;
time_t t;
memset(&sa, 0, sizeof(sa));
sa.sa_handler = handler;
sigaction(SIGALRM, &sa, NULL);
it.it_value.tv_sec = 0;
it.it_value.tv_usec = 1000;
it.it_interval.tv_sec = 0;
it.it_interval.tv_usec = 1000;
setitimer(ITIMER_REAL, &it, NULL);
while(1) {
time(&t);
r = ctime(&t);
}
return 0;
}
