Hi Ilpo,
> On Tue, 31 Jan 2023, Shaopeng Tan wrote:
>
> > After creating a child process with fork() in CAT test, if an error
> > occurs or a signal such as SIGINT is received, the parent process will
> > be terminated immediately, and therefor the child process will not be
> > killed and also resctrlfs is not unmounted.
> >
> > There is a signal handler registered in CMT/MBM/MBA tests, which kills
> > child process, unmount resctrlfs, cleanups result files, etc., if a
> > signal such as SIGINT is received.
> >
> > Commonize the signal handler registered for CMT/MBM/MBA tests and
> > reuse it in CAT too.
> >
> > To reuse the signal handler, make the child process in CAT wait to be
> > killed by parent process in any case (an error occurred or a signal
> > was received), and when killing child process use global bm_pid
> > instead of local bm_pid.
> >
> > Also, since the MBA/MBA/CMT/CAT are run in order, unregister the
> > signal handler at the end of each test so that the signal handler
> > cannot be inherited by other tests.
> >
> > Signed-off-by: Shaopeng Tan <tan.shaopeng@xxxxxxxxxxxxxx>
> > ---
>
> > if (bm_pid == 0) {
> > /* Tell parent that child is ready */
> > close(pipefd[0]);
> > pipe_message = 1;
> > if (write(pipefd[1], &pipe_message, sizeof(pipe_message)) <
> > - sizeof(pipe_message)) {
> > - close(pipefd[1]);
> > + sizeof(pipe_message))
> > + /*
> > + * Just print the error message.
> > + * Let while(1) run and wait for itself to be killed.
> > + */
> > perror("# failed signaling parent process");
>
> If the write error is ignored here, won't it just lead to parent hanging forever
> waiting for the child to send the message through the pipe which will never
> come?
If the write error is ignored here, the pipe will be closed by "close(pipefd[1]);" and child process will wait to be killed by "while(1)".
---
- return errno;
- }
close(pipefd[1]);
while (1)
---
If all file descriptors referring to the write end of a pipe have been closed,
then an attempt to read(2) from the pipe will see end-of-file (read(2) will return 0).
Then, "perror("# failed reading from child process");" occurs.
---
} else {
/* Parent waits for child to be ready. */
close(pipefd[1]);
pipe_message = 0;
while (pipe_message != 1) {
if (read(pipefd[0], &pipe_message,
sizeof(pipe_message)) < sizeof(pipe_message)) {
perror("# failed reading from child process");
break;
}
}
close(pipefd[0]);
kill(bm_pid, SIGKILL);
signal_handler_unregister();
}
---
Best regards,
Shaopeng TAN
