init: Combine two global sigchld_fd variables into one
Remove the Service::SetSigchldFd() method. Make the Service::GetSigchldFd()
create a signalfd for SIGCHLD. This makes it possible to use a SIGCHLD
signalfd in unit tests.
Change-Id: I0b41caa8f46c79f4d400e49aaba5227fad53c251
Signed-off-by: Bart Van Assche <bvanassche@google.com>
diff --git a/init/init.cpp b/init/init.cpp
index 83cb78b..aeccd66 100644
--- a/init/init.cpp
+++ b/init/init.cpp
@@ -117,7 +117,6 @@
static int property_triggers_enabled = 0;
-int sigchld_fd = -1;
static int sigterm_fd = -1;
static int property_fd = -1;
@@ -717,7 +716,7 @@
static void HandleSignalFd(int signal) {
signalfd_siginfo siginfo;
- const int signal_fd = signal == SIGCHLD ? sigchld_fd : sigterm_fd;
+ const int signal_fd = signal == SIGCHLD ? Service::GetSigchldFd() : sigterm_fd;
ssize_t bytes_read = TEMP_FAILURE_RETRY(read(signal_fd, &siginfo, sizeof(siginfo)));
if (bytes_read != sizeof(siginfo)) {
PLOG(ERROR) << "Failed to read siginfo from signal_fd";
@@ -751,20 +750,24 @@
}
}
+static Result<void> RegisterSignalFd(Epoll* epoll, int signal, int fd) {
+ return epoll->RegisterHandler(
+ fd, [signal]() { HandleSignalFd(signal); }, EPOLLIN | EPOLLPRI);
+}
+
static Result<int> CreateAndRegisterSignalFd(Epoll* epoll, int signal) {
sigset_t mask;
sigemptyset(&mask);
sigaddset(&mask, signal);
- unique_fd signal_fd(signalfd(-1, &mask, SFD_CLOEXEC));
- if (signal_fd == -1) {
- return ErrnoError() << "failed to create signalfd for signal " << signal;
+ if (sigprocmask(SIG_BLOCK, &mask, nullptr) == -1) {
+ return ErrnoError() << "failed to block signal " << signal;
}
- auto result = epoll->RegisterHandler(
- signal_fd.get(), [signal]() { HandleSignalFd(signal); }, EPOLLIN | EPOLLPRI);
- if (!result.ok()) {
- return result.error();
+ unique_fd signal_fd(signalfd(-1, &mask, SFD_CLOEXEC));
+ if (signal_fd.get() < 0) {
+ return ErrnoError() << "failed to create signalfd for signal " << signal;
}
+ OR_RETURN(RegisterSignalFd(epoll, signal, signal_fd.get()));
return signal_fd.release();
}
@@ -775,34 +778,18 @@
const struct sigaction act { .sa_flags = SA_NOCLDSTOP, .sa_handler = SIG_DFL };
sigaction(SIGCHLD, &act, nullptr);
- sigset_t mask;
- sigemptyset(&mask);
- sigaddset(&mask, SIGCHLD);
-
- if (!IsRebootCapable()) {
- // If init does not have the CAP_SYS_BOOT capability, it is running in a container.
- // In that case, receiving SIGTERM will cause the system to shut down.
- sigaddset(&mask, SIGTERM);
- }
-
- if (sigprocmask(SIG_BLOCK, &mask, nullptr) == -1) {
- PLOG(FATAL) << "failed to block signals";
- }
-
// Register a handler to unblock signals in the child processes.
const int result = pthread_atfork(nullptr, nullptr, &UnblockSignals);
if (result != 0) {
LOG(FATAL) << "Failed to register a fork handler: " << strerror(result);
}
- Result<int> cs_result = CreateAndRegisterSignalFd(epoll, SIGCHLD);
+ Result<void> cs_result = RegisterSignalFd(epoll, SIGCHLD, Service::GetSigchldFd());
if (!cs_result.ok()) {
PLOG(FATAL) << cs_result.error();
}
- sigchld_fd = cs_result.value();
- Service::SetSigchldFd(sigchld_fd);
- if (sigismember(&mask, SIGTERM)) {
+ if (!IsRebootCapable()) {
Result<int> cs_result = CreateAndRegisterSignalFd(epoll, SIGTERM);
if (!cs_result.ok()) {
PLOG(FATAL) << cs_result.error();
diff --git a/init/init.h b/init/init.h
index b781167..9c7e918 100644
--- a/init/init.h
+++ b/init/init.h
@@ -28,8 +28,6 @@
namespace android {
namespace init {
-extern int sigchld_fd;
-
Parser CreateParser(ActionManager& action_manager, ServiceList& service_list);
Parser CreateApexConfigParser(ActionManager& action_manager, ServiceList& service_list);
diff --git a/init/reboot.cpp b/init/reboot.cpp
index 5757922..1a26c4d 100644
--- a/init/reboot.cpp
+++ b/init/reboot.cpp
@@ -563,7 +563,7 @@
}
}
if (timeout > 0ms) {
- WaitToBeReaped(sigchld_fd, pids, timeout);
+ WaitToBeReaped(Service::GetSigchldFd(), pids, timeout);
} else {
// Even if we don't to wait for services to stop, we still optimistically reap zombies.
ReapAnyOutstandingChildren();
diff --git a/init/service.cpp b/init/service.cpp
index d351a8f..eb24dd5 100644
--- a/init/service.cpp
+++ b/init/service.cpp
@@ -37,6 +37,7 @@
#include <cutils/sockets.h>
#include <processgroup/processgroup.h>
#include <selinux/selinux.h>
+#include <sys/signalfd.h>
#include <string>
@@ -68,6 +69,7 @@
using android::base::SetProperty;
using android::base::StartsWith;
using android::base::StringPrintf;
+using android::base::unique_fd;
using android::base::WriteStringToFile;
namespace android {
@@ -136,7 +138,6 @@
unsigned long Service::next_start_order_ = 1;
bool Service::is_exec_service_running_ = false;
-int Service::sigchld_fd_ = -1;
Service::Service(const std::string& name, Subcontext* subcontext_for_restart_commands,
const std::string& filename, const std::vector<std::string>& args)
@@ -792,6 +793,35 @@
mount_namespace_ = IsDefaultMountNamespaceReady() ? NS_DEFAULT : NS_BOOTSTRAP;
}
+static int ThreadCount() {
+ std::unique_ptr<DIR, decltype(&closedir)> dir(opendir("/proc/self/task"), closedir);
+ if (!dir) {
+ return -1;
+ }
+
+ int count = 0;
+ dirent* entry;
+ while ((entry = readdir(dir.get())) != nullptr) {
+ if (entry->d_name[0] != '.') {
+ count++;
+ }
+ }
+ return count;
+}
+
+// Must be called BEFORE any threads are created. See also the sigprocmask() man page.
+unique_fd Service::CreateSigchldFd() {
+ CHECK_EQ(ThreadCount(), 1);
+ sigset_t mask;
+ sigemptyset(&mask);
+ sigaddset(&mask, SIGCHLD);
+ if (sigprocmask(SIG_BLOCK, &mask, nullptr) < 0) {
+ PLOG(FATAL) << "Failed to block SIGCHLD";
+ }
+
+ return unique_fd(signalfd(-1, &mask, SFD_CLOEXEC));
+}
+
void Service::SetStartedInFirstStage(pid_t pid) {
LOG(INFO) << "adding first-stage service '" << name_ << "'...";
diff --git a/init/service.h b/init/service.h
index 13c8b5f..5e9af25 100644
--- a/init/service.h
+++ b/init/service.h
@@ -156,7 +156,10 @@
const Subcontext* subcontext() const { return subcontext_; }
const std::string& filename() const { return filename_; }
void set_filename(const std::string& name) { filename_ = name; }
- static void SetSigchldFd(int sigchld_fd) { sigchld_fd_ = sigchld_fd; }
+ static int GetSigchldFd() {
+ static int sigchld_fd = CreateSigchldFd().release();
+ return sigchld_fd;
+ }
private:
void NotifyStateChange(const std::string& new_state) const;
@@ -169,10 +172,10 @@
void RunService(const std::vector<Descriptor>& descriptors, InterprocessFifo cgroups_activated,
InterprocessFifo setsid_finished);
void SetMountNamespace();
+ static ::android::base::unique_fd CreateSigchldFd();
static unsigned long next_start_order_;
static bool is_exec_service_running_;
- static int sigchld_fd_;
const std::string name_;
std::set<std::string> classnames_;