Re: [RFC PATCH] tests/tcg: add a multiarch signals test to stress test signal delivery

[Philippe Mathieu-Daudé]

+Laurent

On 4/21/21 3:29 PM, Alex Bennée wrote:
> This adds a simple signal test that combines the POSIX timer_create
> with signal delivery across multiple threads.
> 
> [AJB: So I wrote this in an attempt to flush out issues with the
> s390x-linux-user handling. However I suspect I've done something wrong
> or opened a can of signal handling worms.
> 
> Nominally this runs fine on real hardware but I variously get failures
> when running it under translation and while debugging QEMU running the
> test. I've also exposed a shortcomming with the gdb stub when dealing
> with guest TLS data so yay ;-). So I post this as an RFC in case
> anyone else can offer insight or can verify they are seeing the same
> strange behaviour?]
> 
> Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
> ---
>  tests/tcg/multiarch/signals.c       | 149 ++++++++++++++++++++++++++++
>  tests/tcg/multiarch/Makefile.target |   2 +
>  2 files changed, 151 insertions(+)
>  create mode 100644 tests/tcg/multiarch/signals.c
> 
> diff --git a/tests/tcg/multiarch/signals.c b/tests/tcg/multiarch/signals.c
> new file mode 100644
> index 0000000000..998c8fdefd
> --- /dev/null
> +++ b/tests/tcg/multiarch/signals.c
> @@ -0,0 +1,149 @@
> +/*
> + * linux-user signal handling tests.
> + *
> + * Copyright (c) 2021 Linaro Ltd
> + *
> + * SPDX-License-Identifier: GPL-2.0-or-later
> + */
> +
> +#include <stdarg.h>
> +#include <stdint.h>
> +#include <stdio.h>
> +#include <stdlib.h>
> +#include <unistd.h>
> +#include <errno.h>
> +#include <pthread.h>
> +#include <string.h>
> +#include <signal.h>
> +#include <time.h>
> +#include <sys/time.h>
> +
> +static void error1(const char *filename, int line, const char *fmt, ...)
> +{
> +    va_list ap;
> +    va_start(ap, fmt);
> +    fprintf(stderr, "%s:%d: ", filename, line);
> +    vfprintf(stderr, fmt, ap);
> +    fprintf(stderr, "\n");
> +    va_end(ap);
> +    exit(1);
> +}
> +
> +static int __chk_error(const char *filename, int line, int ret)
> +{
> +    if (ret < 0) {
> +        error1(filename, line, "%m (ret=%d, errno=%d/%s)",
> +               ret, errno, strerror(errno));
> +    }
> +    return ret;
> +}
> +
> +#define error(fmt, ...) error1(__FILE__, __LINE__, fmt, ## __VA_ARGS__)
> +
> +#define chk_error(ret) __chk_error(__FILE__, __LINE__, (ret))
> +
> +/*
> + * Thread handling
> + */
> +typedef struct ThreadJob ThreadJob;
> +
> +struct ThreadJob {
> +    int number;
> +    int sleep;
> +    int count;
> +};
> +
> +static pthread_t *threads;
> +static int max_threads = 10;
> +__thread int signal_count;
> +int total_signal_count;
> +
> +static void *background_thread_func(void *arg)
> +{
> +    ThreadJob *job = (ThreadJob *) arg;
> +
> +    printf("thread%d: started\n", job->number);
> +    while (total_signal_count < job->count) {
> +        usleep(job->sleep);
> +    }
> +    printf("thread%d: saw %d alarms from %d\n", job->number,
> +           signal_count, total_signal_count);
> +    return NULL;
> +}
> +
> +static void spawn_threads(void)
> +{
> +    int i;
> +    threads = calloc(sizeof(pthread_t), max_threads);
> +
> +    for (i = 0; i < max_threads; i++) {
> +        ThreadJob *job = calloc(sizeof(ThreadJob), 1);
> +        job->number = i;
> +        job->sleep = i * 1000;
> +        job->count = i * 100;
> +        pthread_create(threads + i, NULL, background_thread_func, job);
> +    }
> +}
> +
> +static void close_threads(void)
> +{
> +    int i;
> +    for (i = 0; i < max_threads; i++) {
> +        pthread_join(threads[i], NULL);
> +    }
> +    free(threads);
> +    threads = NULL;
> +}
> +
> +static void sig_alarm(int sig, siginfo_t *info, void *puc)
> +{
> +    if (sig != SIGRTMIN) {
> +        error("unexpected signal");
> +    }
> +    signal_count++;
> +    __atomic_fetch_add(&total_signal_count, 1, __ATOMIC_SEQ_CST);
> +}
> +
> +static void test_signals(void)
> +{
> +    struct sigaction act;
> +    struct itimerspec it;
> +    timer_t tid;
> +    struct sigevent sev;
> +
> +    /* Set up SIG handler */
> +    act.sa_sigaction = sig_alarm;
> +    sigemptyset(&act.sa_mask);
> +    act.sa_flags = SA_SIGINFO;
> +    chk_error(sigaction(SIGRTMIN, &act, NULL));
> +
> +    /* Create POSIX timer */
> +    sev.sigev_notify = SIGEV_SIGNAL;
> +    sev.sigev_signo = SIGRTMIN;
> +    sev.sigev_value.sival_ptr = &tid;
> +    chk_error(timer_create(CLOCK_REALTIME, &sev, &tid));
> +
> +    it.it_interval.tv_sec = 0;
> +    it.it_interval.tv_nsec = 1000000;
> +    it.it_value.tv_sec = 0;
> +    it.it_value.tv_nsec = 1000000;
> +    chk_error(timer_settime(tid, 0, &it, NULL));
> +
> +    spawn_threads();
> +
> +    do {
> +        usleep(1000);
> +    } while (total_signal_count < 2000);
> +
> +    printf("shutting down after: %d signals\n", total_signal_count);
> +
> +    close_threads();
> +
> +    chk_error(timer_delete(tid));
> +}
> +
> +int main(int argc, char **argv)
> +{
> +    test_signals();
> +    return 0;
> +}
> diff --git a/tests/tcg/multiarch/Makefile.target 
> b/tests/tcg/multiarch/Makefile.target
> index a3a751723d..3f283eabe6 100644
> --- a/tests/tcg/multiarch/Makefile.target
> +++ b/tests/tcg/multiarch/Makefile.target
> @@ -30,6 +30,8 @@ testthread: LDFLAGS+=-lpthread
>  
>  threadcount: LDFLAGS+=-lpthread
>  
> +signals: LDFLAGS+=-lrt -lpthread
> +
>  # We define the runner for test-mmap after the individual
>  # architectures have defined their supported pages sizes. If no
>  # additional page sizes are defined we only run the default test.
>