Hello,
I found fork() fails if it is called recursively from a child thread.
Simple test case, attached (fk.c), reproduces this problem.
Expected result:
Parent 0 [22034] exit.
Child 0 [22036] works.
Parent 1 [22036] exit.
Child 1 [22038] works.
Parent 2 [22038] exit.
Child 2 [22039] works.
Parent 3 [22039] exit.
Child 3 [22040] works.
Parent 4 [22040] exit.
Child 4 [22041] works.
Result in cygwin 2.7.0:
Child 0 [4668] works.
Parent 0 [7188] exit.
0 [main] a 4668 fork: child -1 - forked process 8456 died unexpectedly,
retry 0, exit code 0xC0000142, errno 11
fork(): Resource temporarily unavailable
Strictly speaking, the test case is not safe because it calls functions
which are not async-signal-safe from forked child process, i.e. printf()
and perror(), in spite of multi-thread. However the same happens even
without printf() and perror().
This is the cause of which iperf 2.0.5 with option -s -D fails to start
as daemon.
Is this the known issue?
--
Takashi Yano <takashi.y...@nifty.ne.jp>
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <signal.h>
#include <pthread.h>
void MoveToChild(int n)
{
pid_t pid;
if ( (pid = fork()) == -1 ) {
perror("fork()");
_exit(1);
} else if ( pid != 0 ) {
printf("Parent %d [%d] exit.\n", n, getpid());
_exit(0);
}
printf("Child %d [%d] works.\n", n, getpid());
}
void *thread_main(void *args)
{
int i;
for (i=0; i<5; i++) MoveToChild(i);
return NULL;
}
int main()
{
pthread_t t;
pthread_create(&t, NULL, thread_main, NULL);
pthread_join(t, NULL);
return 0;
}
--
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