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Commit 97047b54 authored by Bart Van Assche's avatar Bart Van Assche
Browse files

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: default avatarBart Van Assche <bvanassche@google.com>
parent ced62e53

init/init.cpp

+14 −27
Original line number Diff line number Diff line
@@ -117,7 +117,6 @@ namespace init { 


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 HandleSigtermSignal(const signalfd_siginfo& siginfo) { 


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 void UnblockSignals() { 
    }

}



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 @@ static void InstallSignalFdHandler(Epoll* epoll) { 
    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();

init/init.h

+0 −2
Original line number Diff line number Diff line
@@ -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);

init/reboot.cpp

+1 −1
Original line number Diff line number Diff line
@@ -563,7 +563,7 @@ static void StopServices(const std::set<std::string>& services, std::chrono::mil 
        }

    }

    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();

init/service.cpp

+31 −1
Original line number Diff line number Diff line
@@ -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::make_scope_guard; 
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 @@ static bool ExpandArgsAndExecv(const std::vector<std::string>& args, bool sigsto 


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 @@ void Service::SetMountNamespace() { 
    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_ << "'...";

init/service.h

+5 −2
Original line number Diff line number Diff line
@@ -156,7 +156,10 @@ class Service { 
    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 @@ class Service { 
    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_;