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Add SIGCHLD handler to pause container

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This allows pause to reap zombies in the upcoming Shared PID namespace
(#1615). Uses the better defined sigaction() instead of signal() for all
signals both for consistency (SIGCHLD handler avoids SA_RESTART) and to
avoid the implicit signal()->sigaction() translation of various libc
versions.

Also makes warnings errors and includes a tool to make orphaned zombies
for manual testing.
This commit is contained in:
Lee Verberne 2016-11-14 11:30:33 +00:00
parent 15059e6a5b
commit 81d27aa239
3 changed files with 64 additions and 5 deletions
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35
build-tools/pause/orphan.c Normal file
View File

@ -0,0 +1,35 @@
/*
Copyright 2016 The Kubernetes Authors.
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/
/* Creates a zombie to be reaped by init. Useful for testing. */
#include <stdio.h>
#include <unistd.h>
int main() {
pid_t pid;
pid = fork();
if ( pid == 0 ) {
while ( getppid() > 1 );
printf("Child exiting: pid=%d ppid=%d\n", getpid(), getppid());
return 0;
} else if ( pid > 0 ) {
printf("Parent exiting: pid=%d ppid=%d\n", getpid(), getppid());
return 0;
}
perror("Could not create child");
return 1;
}

15
build/pause/Makefile
View File

@ -12,7 +12,7 @@
# See the License for the specific language governing permissions and
# limitations under the License.
.PHONY: all push push-legacy container clean
.PHONY: all push push-legacy container clean orphan
REGISTRY ?= gcr.io/google_containers
IMAGE = $(REGISTRY)/pause-$(ARCH)
@ -25,7 +25,7 @@ ARCH ?= amd64
ALL_ARCH = amd64 arm arm64 ppc64le s390x
CFLAGS = -Os -Wall -static
CFLAGS = -Os -Wall -Werror -static
KUBE_CROSS_IMAGE ?= gcr.io/google_containers/kube-cross
KUBE_CROSS_VERSION ?= $(shell cat ../build-image/cross/VERSION)
@ -97,5 +97,16 @@ ifeq ($(ARCH),amd64)
endif
touch $@
# Useful for testing, not automatically included in container image
orphan: bin/orphan-$(ARCH)
bin/orphan-$(ARCH): orphan.c
mkdir -p bin
docker run -u $$(id -u):$$(id -g) -v $$(pwd):/build \
$(KUBE_CROSS_IMAGE):$(KUBE_CROSS_VERSION) \
/bin/bash -c "\
cd /build && \
$(TRIPLE)-gcc $(CFLAGS) -o $@ $^ && \
$(TRIPLE)-strip $@"
clean:
rm -rf .container-* .push-* bin/

19
build/pause/pause.c
View File

@ -17,6 +17,8 @@ limitations under the License.
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <unistd.h>
static void sigdown(int signo) {
@ -24,12 +26,23 @@ static void sigdown(int signo) {
exit(0);
}
static void sigreap(int signo) {
while (waitpid(-1, NULL, WNOHANG) > 0);
}
int main() {
if (signal(SIGINT, sigdown) == SIG_ERR)
if (getpid() != 1) {
fprintf(stderr, "Warning: pause should be the first process in a pod\n");
}
if (sigaction(SIGINT, &(struct sigaction){.sa_handler = sigdown}, NULL) < 0)
return 1;
if (signal(SIGTERM, sigdown) == SIG_ERR)
if (sigaction(SIGTERM, &(struct sigaction){.sa_handler = sigdown}, NULL) < 0)
return 2;
signal(SIGKILL, sigdown);
if (sigaction(SIGCHLD, &(struct sigaction){.sa_handler = sigreap, .sa_flags = SA_NOCLDSTOP}, NULL) < 0)
return 3;
sigaction(SIGKILL, &(struct sigaction){.sa_handler = sigdown}, NULL);
for (;;) pause();
fprintf(stderr, "error: infinite loop terminated\n");
return 42;