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Commit 43323a7e authored by Bart Van Assche's avatar Bart Van Assche
Browse files

init: Create different file descriptors for SIGCHLD and SIGTERM 



This change will allow a later CL to wait for SIGCHLD without discarding
the SIGTERM information.

Bug: 308687042
Change-Id: I5b9ab4562060455573cd816cc48bf90576b39ab9
Signed-off-by: default avatarBart Van Assche <bvanassche@google.com>
parent 6c7dca81

init/init.cpp

+33 −8
Original line number Diff line number Diff line
@@ -108,6 +108,7 @@ using android::base::SetProperty; 
using android::base::StringPrintf;

using android::base::Timer;

using android::base::Trim;

using android::base::unique_fd;

using android::fs_mgr::AvbHandle;

using android::snapshot::SnapshotManager;
@@ -116,7 +117,8 @@ namespace init { 


static int property_triggers_enabled = 0;



static int signal_fd = -1;

static int sigchld_fd = -1;

static int sigterm_fd = -1;

static int property_fd = -1;



struct PendingControlMessage {
@@ -713,8 +715,9 @@ static void HandleSigtermSignal(const signalfd_siginfo& siginfo) { 
    HandlePowerctlMessage("shutdown,container");

}



static void HandleSignalFd() {

static void HandleSignalFd(int signal) {

    signalfd_siginfo siginfo;

    const int signal_fd = signal == SIGCHLD ? sigchld_fd : 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";
@@ -748,6 +751,24 @@ static void UnblockSignals() { 
    }

}



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;

    }



    auto result = epoll->RegisterHandler(

            signal_fd.get(), [signal]() { HandleSignalFd(signal); }, EPOLLIN | EPOLLPRI);

    if (!result.ok()) {

        return result.error();

    }



    return signal_fd.release();

}



static void InstallSignalFdHandler(Epoll* epoll) {

    // Applying SA_NOCLDSTOP to a defaulted SIGCHLD handler prevents the signalfd from receiving

    // SIGCHLD when a child process stops or continues (b/77867680#comment9).
@@ -774,14 +795,18 @@ static void InstallSignalFdHandler(Epoll* epoll) { 
        LOG(FATAL) << "Failed to register a fork handler: " << strerror(result);

    }



    signal_fd = signalfd(-1, &mask, SFD_CLOEXEC);

    if (signal_fd == -1) {

        PLOG(FATAL) << "failed to create signalfd";

    Result<int> cs_result = CreateAndRegisterSignalFd(epoll, SIGCHLD);

    if (!cs_result.ok()) {

        PLOG(FATAL) << cs_result.error();

    }

    sigchld_fd = cs_result.value();



    constexpr int flags = EPOLLIN | EPOLLPRI;

    if (auto result = epoll->RegisterHandler(signal_fd, HandleSignalFd, flags); !result.ok()) {

        LOG(FATAL) << result.error();

    if (sigismember(&mask, SIGTERM)) {

        Result<int> cs_result = CreateAndRegisterSignalFd(epoll, SIGTERM);

        if (!cs_result.ok()) {

            PLOG(FATAL) << cs_result.error();

        }

        sigterm_fd = cs_result.value();

    }

}