Messages in this thread | | | Date | Thu, 18 Nov 2004 12:30:16 +0100 | From | (Klaus Dittrich) | Subject | kernel reports kill too late? |
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With kernels newer 2.6.10.rc1-bk18 glibc nptl checks failed.
Now this is fixed (See lkml "Futex queue_me/get_user ordering") another problem showed off.
I get spurious "Failed to kill test process: No child processes" errors during nptl checks now.
Appended is a simple test-prog derived from glibc's check which runs fine on 2.6.10.rc1-bk18 but failed most of the time with newer kernels.
(Not beeing a guru at all) I interpret the results as a delay or loss of the status of a killed process which happens only if this process runs a thread. (Not calling sleep_mostly() as a thread works as expected.)
Further noteworthy: it happens not always.
Output on 2.6.10.rc1-bk18 thread starts spinning thread alive try to kill pid 1436 killed after 4007 waitpid calls killed by signal: status = 0
Output on 2.6.10.rc2-bk2 test 0 -------------------------------- thread starts spinning thread alive try to kill pid 32321 killed after 3389 waitpid calls killed by signal: status = 0 test 1 -------------------------------- thread starts spinning thread alive try to kill pid 32323 killed after 17 waitpid calls killed by signal: status = 138 Kill failed! waitpid returned -1
Both systems are smp 2xP4 and 2xP3.
Can anyone else see this?
-- Regards Klaus
#include <sys/wait.h> #include <signal.h> #include <stdio.h> #include <stdlib.h> #include <unistd.h> #include <string.h> #include <errno.h> #include <pthread.h>
static void print_exit_status (int status) {
if(WIFEXITED(status)) { printf("killed normal : status = %d\n", WEXITSTATUS(status)); } else if (WIFSIGNALED(status)) { printf("killed by signal: status = %d\n", WEXITSTATUS(status)); } }
static void * sleep_mostly (void * arg) { printf("thread starts spinning\n");
while (1) { sleep (1); printf ("thread alive\n"); }
/* NOTREACHED */ return NULL; }
static int do_fork (void) { pid_t pid = fork (); if (pid == 0) { /* child */
pthread_t th; int cr = pthread_create (&th, NULL, sleep_mostly, (void*)NULL);
if (cr != 0) { fprintf (stderr, "Thread creation failed %s\n", strerror(cr)); exit (1); }
sleep(3); pthread_exit (NULL); } else if (pid < 0) { fprintf (stderr, "Cannot fork!\n"); exit (1); } return pid; }
static int test_wait_pid(void) {
int pid = do_fork();
sleep(2); fprintf (stderr, "try to kill pid %d\n", pid); kill (pid, SIGKILL);
int killed; int status; int n;
for (n = 1; n < 9999; n++) { killed = waitpid (pid, &status, WNOHANG|WUNTRACED); if (killed != 0) break; }
fprintf (stderr, "killed after %d waitpid calls\n", n); print_exit_status(status);
if (killed != 0 && killed != pid) { fprintf (stderr, "Kill failed! waitpid returned %d\n", killed); exit (1); }
return 0; }
int main (int argc, char* argv[]) {
int i = 0; do { printf ("test %d --------------------------------\n", i); test_wait_pid(); i++; } while ( i < 10); return 0; }
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