Re: [PATCH net-next v2 3/3] connector/cn_proc: Selftest for threads

[Liam R. Howlett]

* Anjali Kulkarni <anjali.k.kulkarni@xxxxxxxxxx> [241015 13:30]:
> Test to check if setting PROC_CN_MCAST_NOTIFY in proc connector API, allows
> a thread's non-zero exit status to be returned to proc_filter.
> 
> The threads.c program creates 2 child threads. 1st thread handles signal
> SIGSEGV, and 2nd thread needs to indicate some error condition (value 1)
> to the kernel, instead of using pthread_exit() with 1.
> 
> In both cases, child sends notify_netlink_thread_exit(exit_code) to kernel,
> to let kernel know it has exited abnormally with exit_code.
> 
> Compile:
>     make thread
>     make proc_filter
> To see non-zero exit notifications, run:
>     ./proc_filter -f
> Run threads code in another window:
>     ./threads
> Note the 2 child thread IDs reported above
> Send SIGSEGV signal to the child handling SIGSEGV:
>     kill -11 <child1-tid>
> Watch the child 1 tid being notified with exit code 11 to proc_filter
> Watch child 2 tid being notified with exit code 1 (value defined in code)
> to proc_filter
> 
> Signed-off-by: Anjali Kulkarni <anjali.k.kulkarni@xxxxxxxxxx>
> ---
>  tools/testing/selftests/connector/Makefile    |  23 +++-
>  .../testing/selftests/connector/proc_filter.c |   5 +
>  tools/testing/selftests/connector/thread.c    | 116 ++++++++++++++++++
>  .../selftests/connector/thread_filter.c       |  96 +++++++++++++++
>  4 files changed, 239 insertions(+), 1 deletion(-)
>  create mode 100644 tools/testing/selftests/connector/thread.c
>  create mode 100644 tools/testing/selftests/connector/thread_filter.c
> 
> diff --git a/tools/testing/selftests/connector/Makefile b/tools/testing/selftests/connector/Makefile
> index 92188b9bac5c..bf335826bc3b 100644
> --- a/tools/testing/selftests/connector/Makefile
> +++ b/tools/testing/selftests/connector/Makefile
> @@ -1,5 +1,26 @@
>  # SPDX-License-Identifier: GPL-2.0
> -CFLAGS += -Wall $(KHDR_INCLUDES)
> +KERNEL="../../../.."
> +
> +CFLAGS += -Wall $(KHDR_INCLUDES) -I $(KERNEL)/include/uapi -I $(KERNEL)/include
> +
> +proc_filter: proc_filter.o
> +	cc proc_filter.o -o proc_filter
> +
> +proc_filter.o: proc_filter.c
> +	cc -c proc_filter.c -o proc_filter.o $(CFLAGS)
> +
> +thread: thread.o thread_filter.o
> +	cc thread.o thread_filter.o -o thread
> +
> +thread.o: thread.c $(DEPS)
> +		cc -c thread.c -o thread.o $(CFLAGS)
> +
> +thread_filter.o: thread_filter.c
> +		cc -c thread_filter.c -o thread_filter.o $(CFLAGS)
> +
> +define EXTRA_CLEAN
> +	rm *.o thread
> +endef
>  
>  TEST_GEN_PROGS = proc_filter
>  
> diff --git a/tools/testing/selftests/connector/proc_filter.c b/tools/testing/selftests/connector/proc_filter.c
> index 4a825b997666..6fb4842894f8 100644
> --- a/tools/testing/selftests/connector/proc_filter.c
> +++ b/tools/testing/selftests/connector/proc_filter.c
> @@ -1,4 +1,9 @@
>  // SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Author: Anjali Kulkarni <anjali.k.kulkarni@xxxxxxxxxx>
> + *
> + * Copyright (c) 2024 Oracle and/or its affiliates.
> + */
>  
>  #include <sys/types.h>
>  #include <sys/epoll.h>
> diff --git a/tools/testing/selftests/connector/thread.c b/tools/testing/selftests/connector/thread.c
> new file mode 100644
> index 000000000000..8c9abf6115d6
> --- /dev/null
> +++ b/tools/testing/selftests/connector/thread.c
> @@ -0,0 +1,116 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Author: Anjali Kulkarni <anjali.k.kulkarni@xxxxxxxxxx>
> + *
> + * Copyright (c) 2024 Oracle and/or its affiliates.
> + */
> +
> +#include <pthread.h>
> +#include <stdio.h>
> +#include <unistd.h>
> +#include <stdlib.h>
> +#include <signal.h>
> +
> +/*
> + * This code tests a thread exit notification when thread exits abnormally.
> + * Normally, when a thread exits abnormally, the kernel is not aware of the
> + * exit code. This is usually only conveyed from child to parent via the
> + * pthread_exit() and pthread_join() calls. Sometimes, however, a parent
> + * process cannot monitor all child processes via pthread_join(), particularly
> + * when there is a huge amount of child processes. In this case, the parent
> + * has created the child with PTHREAD_CREATE_DETACHED attribute.
> + * To fix this problem, either when child wants to convey non-zero exit via
> + * pthread_exit() or in a signal handler, the child can notify the kernel's
> + * connector module it's exit status via a netlink call with new type
> + * PROC_CN_MCAST_NOTIFY. (Implemented in the thread_filter.c file).
> + * This will send the exit code from the child to the kernel, which the kernel
> + * can later return to proc_filter program when the child actually exits.
> + * To test this usecase:
> + * Compile:
> + *	make thread
> + *	make proc_filter
> + * To see non-zero exit notifications, run:
> + *	./proc_filter -f
> + * Start the threads code, creating 2 threads, in another window:
> + *	./threads
> + * Note the 2 child thread IDs reported above
> + * Send SIGSEGV signal to the child handling SIGSEGV:
> + *	kill -11 <child1-tid>
> + * Watch the event being notified with exit code 11 to proc_filter
> + * Watch child 2 tid being notified with exit code 1 (value defined in code)
> + * to proc_filter
> + */
> +
> +extern int notify_netlink_thread_exit(unsigned int exit_code);
> +
> +static void sigsegvh(int sig)
> +{
> +	unsigned int exit_code = (unsigned int) sig;
> +	/*
> +	 * Send any non-zero value to get a notification. Here we are
> +	 * sending the signal number for SIGSEGV which is 11
> +	 */
> +	notify_netlink_thread_exit(exit_code);
> +}
> +
> +void *threadc1(void *ptr)
> +{
> +	signal(SIGSEGV, sigsegvh);
> +	printf("Child 1 thread id %d, handling SIGSEGV\n", gettid());
> +	sleep(20);
> +	pthread_exit(NULL);
> +}
> +
> +void *threadc2(void *ptr)
> +{
> +	int exit_val = 1;
> +
> +	printf("Child 2 thread id %d, wants to exit with value %d\n",
> +			gettid(), exit_val);
> +	sleep(2);
> +	notify_netlink_thread_exit(exit_val);
> +	pthread_exit(NULL);
> +}
> +
> +int main(int argc, char **argv)
> +{
> +	pthread_t thread1, thread2;
> +	pthread_attr_t attr1, attr2;
> +	int ret;
> +
> +	ret = pthread_attr_init(&attr1);
> +	if (ret != 0) {
> +		perror("pthread_attr_init failed");
> +		exit(ret);
> +	}
> +	ret = pthread_attr_setdetachstate(&attr1, PTHREAD_CREATE_DETACHED);
> +	if (ret != 0) {
> +		perror("pthread_attr_setdetachstate failed");
> +		exit(ret);
> +	}
> +	ret = pthread_create(&thread1, &attr1, *threadc1, NULL);
> +	if (ret != 0) {
> +		perror("pthread_create failed");
> +		exit(ret);
> +	}
> +
> +	ret = pthread_attr_init(&attr2);
> +	if (ret != 0) {
> +		perror("pthread_attr_init failed");
> +		exit(ret);
> +	}
> +	ret = pthread_attr_setdetachstate(&attr2, PTHREAD_CREATE_DETACHED);
> +	if (ret != 0) {
> +		perror("pthread_attr_setdetachstate failed");
> +		exit(ret);
> +	}
> +	ret = pthread_create(&thread2, &attr2, *threadc2, NULL);
> +	if (ret != 0) {
> +		perror("pthread_create failed");
> +		exit(ret);
> +	}

I expected the test to check for the correct value to be returned?
Could you use pthread_join() and verify the same value is returned
through the new mechanism, or will they not match?

> +
> +	/* Wait for children to exit or be killed */
> +	sleep(30);
> +	exit(0);
> +}
> diff --git a/tools/testing/selftests/connector/thread_filter.c b/tools/testing/selftests/connector/thread_filter.c
> new file mode 100644
> index 000000000000..3da740aa7537
> --- /dev/null
> +++ b/tools/testing/selftests/connector/thread_filter.c
> @@ -0,0 +1,96 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Author: Anjali Kulkarni <anjali.k.kulkarni@xxxxxxxxxx>
> + *
> + * Copyright (c) 2024 Oracle and/or its affiliates.
> + */
> +
> +#include <sys/types.h>
> +#include <sys/epoll.h>
> +#include <sys/socket.h>
> +#include <linux/netlink.h>
> +#include <linux/connector.h>
> +#include <linux/cn_proc.h>
> +
> +#include <stddef.h>
> +#include <stdio.h>
> +#include <stdlib.h>
> +#include <unistd.h>
> +#include <strings.h>
> +#include <errno.h>
> +#include <signal.h>
> +#include <string.h>
> +
> +#define NL_MESSAGE_SIZE (sizeof(struct nlmsghdr) + sizeof(struct cn_msg) + \
> +			sizeof(struct proc_input))
> +
> +/*
> + * Send PROC_CN_MCAST_NOTIFY type notification to the connector code in kernel.
> + * This will send the exit_code specified by user to the connector layer, so
> + * it can send a notification for that event to any listening process
> + */
> +int send_message(int nl_sock, unsigned int exit_code)
> +{
> +	char buff[NL_MESSAGE_SIZE];
> +	struct nlmsghdr *hdr;
> +	struct cn_msg *msg;
> +
> +	hdr = (struct nlmsghdr *)buff;
> +	hdr->nlmsg_len = NL_MESSAGE_SIZE;
> +	hdr->nlmsg_type = NLMSG_DONE;
> +	hdr->nlmsg_flags = 0;
> +	hdr->nlmsg_seq = 0;
> +	hdr->nlmsg_pid = getpid();
> +
> +	msg = (struct cn_msg *)NLMSG_DATA(hdr);
> +	msg->id.idx = CN_IDX_PROC;
> +	msg->id.val = CN_VAL_PROC;
> +	msg->seq = 0;
> +	msg->ack = 0;
> +	msg->flags = 0;
> +
> +	msg->len = sizeof(struct proc_input);
> +	((struct proc_input *)msg->data)->mcast_op =
> +		PROC_CN_MCAST_NOTIFY;
> +	((struct proc_input *)msg->data)->uexit_code = exit_code;
> +
> +	if (send(nl_sock, hdr, hdr->nlmsg_len, 0) == -1) {
> +		perror("send failed");
> +		return -errno;
> +	}
> +	return 0;
> +}
> +
> +int notify_netlink_thread_exit(unsigned int exit_code)
> +{
> +	struct sockaddr_nl sa_nl;
> +	int err = 0;
> +	int nl_sock;
> +
> +	nl_sock = socket(PF_NETLINK, SOCK_DGRAM, NETLINK_CONNECTOR);
> +
> +	if (nl_sock == -1) {
> +		perror("socket failed");
> +		return -errno;
> +	}
> +
> +	bzero(&sa_nl, sizeof(sa_nl));
> +	sa_nl.nl_family = AF_NETLINK;
> +	sa_nl.nl_groups = CN_IDX_PROC;
> +	sa_nl.nl_pid    = gettid();
> +
> +	if (bind(nl_sock, (struct sockaddr *)&sa_nl, sizeof(sa_nl)) == -1) {
> +		perror("bind failed");
> +		close(nl_sock);
> +		return -errno;
> +	}
> +
> +	err = send_message(nl_sock, exit_code);
> +
> +	close(nl_sock);
> +
> +	if (err < 0)
> +		return err;
> +
> +	return 0;
> +}
> -- 
> 2.46.0
>