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Add a test of behavior under multi-threaded forking.

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Forking a multithreaded process is dangerous but allowed, so long as the child
only executes async-signal-safe functions (e.g. exec).  Add a test to ensure
that we don't break this behavior.
This commit is contained in:
David Goldblatt 2017-07-10 13:19:31 -07:00 committed by David Goldblatt
parent 0a4f5a7eea
commit fb6787a78c
1 changed files with 87 additions and 21 deletions
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108
test/unit/fork.c
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@ -4,6 +4,30 @@
#include <sys/wait.h>
#endif
#ifndef _WIN32
static void
wait_for_child_exit(int pid) {
int status;
while (true) {
if (waitpid(pid, &status, 0) == -1) {
test_fail("Unexpected waitpid() failure.");
}
if (WIFSIGNALED(status)) {
test_fail("Unexpected child termination due to "
"signal %d", WTERMSIG(status));
break;
}
if (WIFEXITED(status)) {
if (WEXITSTATUS(status) != 0) {
test_fail("Unexpected child exit value %d",
WEXITSTATUS(status));
}
break;
}
}
}
#endif
TEST_BEGIN(test_fork) {
#ifndef _WIN32
void *p;
@ -40,26 +64,67 @@ TEST_BEGIN(test_fork) {
/* Child. */
_exit(0);
} else {
int status;
wait_for_child_exit(pid);
}
#else
test_skip("fork(2) is irrelevant to Windows");
#endif
}
TEST_END
/* Parent. */
while (true) {
if (waitpid(pid, &status, 0) == -1) {
test_fail("Unexpected waitpid() failure");
}
if (WIFSIGNALED(status)) {
test_fail("Unexpected child termination due to "
"signal %d", WTERMSIG(status));
break;
}
if (WIFEXITED(status)) {
if (WEXITSTATUS(status) != 0) {
test_fail(
"Unexpected child exit value %d",
WEXITSTATUS(status));
}
break;
}
#ifndef _WIN32
static void *
do_fork_thd(void *arg) {
malloc(1);
int pid = fork();
if (pid == -1) {
/* Error. */
test_fail("Unexpected fork() failure");
} else if (pid == 0) {
/* Child. */
char *args[] = {"true", NULL};
execvp(args[0], args);
test_fail("Exec failed");
} else {
/* Parent */
wait_for_child_exit(pid);
}
return NULL;
}
#endif
#ifndef _WIN32
static void
do_test_fork_multithreaded() {
thd_t child;
thd_create(&child, do_fork_thd, NULL);
do_fork_thd(NULL);
thd_join(child, NULL);
}
#endif
TEST_BEGIN(test_fork_multithreaded) {
#ifndef _WIN32
/*
* We've seen bugs involving hanging on arenas_lock (though the same
* class of bugs can happen on any mutex). The bugs are intermittent
* though, so we want to run the test multiple times. Since we hold the
* arenas lock only early in the process lifetime, we can't just run
* this test in a loop (since, after all the arenas are initialized, we
* won't acquire arenas_lock any further). We therefore repeat the test
* with multiple processes.
*/
for (int i = 0; i < 100; i++) {
int pid = fork();
if (pid == -1) {
/* Error. */
test_fail("Unexpected fork() failure,");
} else if (pid == 0) {
/* Child. */
do_test_fork_multithreaded();
_exit(0);
} else {
wait_for_child_exit(pid);
}
}
#else
@ -70,6 +135,7 @@ TEST_END
int
main(void) {
return test(
test_fork);
return test_no_reentrancy(
test_fork,
test_fork_multithreaded);
}