tequilaOS/platform_system_core
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init: use an eventfd instead of socketpair to wake the main loop

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eventfd is a more suitable mechanism.

Bug: 150863651
Test: boot CF, ctl.start services, reboot CF
Merged-In: Ie5c3b0c048afdd7afa4bfc4cba26bec3225925e5
Change-Id: Ie5c3b0c048afdd7afa4bfc4cba26bec3225925e5
(cherry picked from commit 40463336a8)
This commit is contained in:
Tom Cherry 2020-03-26 20:32:17 -07:00
parent 3a5e138964
commit 9c83185c1e
1 changed files with 18 additions and 21 deletions
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39
init/init.cpp
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@ -22,6 +22,7 @@
#include <signal.h>
#include <stdlib.h>
#include <string.h>
#include <sys/eventfd.h>
#include <sys/mount.h>
#include <sys/signalfd.h>
#include <sys/types.h>
@ -114,30 +115,26 @@ static std::queue<PendingControlMessage> pending_control_messages;
// to fill that socket and deadlock the system. Now we use locks to handle the property changes
// directly in the property thread, however we still must wake the epoll to inform init that there
// is a change to process, so we use this FD. It is non-blocking, since we do not care how many
// times WakeEpoll() is called, only that the epoll will wake.
static int wake_epoll_fd = -1;
// times WakeMainInitThread() is called, only that the epoll will wake.
static int wake_main_thread_fd = -1;
static void InstallInitNotifier(Epoll* epoll) {
int sockets[2];
if (socketpair(AF_UNIX, SOCK_STREAM | SOCK_CLOEXEC | SOCK_NONBLOCK, 0, sockets) != 0) {
PLOG(FATAL) << "Failed to socketpair() between property_service and init";
wake_main_thread_fd = eventfd(0, EFD_CLOEXEC);
if (wake_main_thread_fd == -1) {
PLOG(FATAL) << "Failed to create eventfd for waking init";
}
int epoll_fd = sockets[0];
wake_epoll_fd = sockets[1];
auto drain_socket = [epoll_fd] {
char buf[512];
while (read(epoll_fd, buf, sizeof(buf)) > 0) {
}
auto clear_eventfd = [] {
uint64_t counter;
TEMP_FAILURE_RETRY(read(wake_main_thread_fd, &counter, sizeof(counter)));
};
if (auto result = epoll->RegisterHandler(epoll_fd, drain_socket); !result.ok()) {
if (auto result = epoll->RegisterHandler(wake_main_thread_fd, clear_eventfd); !result.ok()) {
LOG(FATAL) << result.error();
}
}
static void WakeEpoll() {
constexpr char value[] = "1";
TEMP_FAILURE_RETRY(write(wake_epoll_fd, value, sizeof(value)));
static void WakeMainInitThread() {
uint64_t counter = 1;
TEMP_FAILURE_RETRY(write(wake_main_thread_fd, &counter, sizeof(counter)));
}
static class PropWaiterState {
@ -181,7 +178,7 @@ static class PropWaiterState {
LOG(INFO) << "Wait for property '" << wait_prop_name_ << "=" << wait_prop_value_
<< "' took " << *waiting_for_prop_;
ResetWaitForPropLocked();
WakeEpoll();
WakeMainInitThread();
}
}
}
@ -229,7 +226,7 @@ static class ShutdownState {
auto lock = std::lock_guard{shutdown_command_lock_};
shutdown_command_ = command;
do_shutdown_ = true;
WakeEpoll();
WakeMainInitThread();
}
std::optional<std::string> CheckShutdown() {
@ -313,7 +310,7 @@ void PropertyChanged(const std::string& name, const std::string& value) {
if (property_triggers_enabled) {
ActionManager::GetInstance().QueuePropertyChange(name, value);
WakeEpoll();
WakeMainInitThread();
}
prop_waiter_state.CheckAndResetWait(name, value);
@ -439,7 +436,7 @@ bool QueueControlMessage(const std::string& message, const std::string& name, pi
return false;
}
pending_control_messages.push({message, name, pid, fd});
WakeEpoll();
WakeMainInitThread();
return true;
}
@ -465,7 +462,7 @@ static void HandleControlMessages() {
}
// If we still have items to process, make sure we wake back up to do so.
if (!pending_control_messages.empty()) {
WakeEpoll();
WakeMainInitThread();
}
}