Switch init to epoll.

Not just because it's what the cool kids are doing --- it also lets us
simplify the inner loop and decouple it from whatever systems want to
be woken to perform some activity if there's data to be read on some fd.

Currently this is just used to clean up the existing signal handling,
keychord, and property service code.

Change-Id: I4d7541a2c4386957ad877df69e3be08b96a7dec5

8 files changed, 60 insertions, 87 deletions

diff --git a/init/init.cpp b/init/init.cpp
index 4ed23b6..90cbea0 100644
--- a/init/init.cpp
+++ b/init/init.cpp
@@ -25,8 +25,8 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include <sys/epoll.h>
 #include <sys/mount.h>
-#include <sys/poll.h>
 #include <sys/socket.h>
 #include <sys/stat.h>
 #include <sys/types.h>
@@ -82,6 +82,17 @@ static const char *ENV[32];
 
 bool waiting_for_exec = false;
 
+static int epoll_fd = -1;
+
+void register_epoll_handler(int fd, void (*fn)()) {
+    epoll_event ev;
+    ev.events = EPOLLIN;
+    ev.data.ptr = reinterpret_cast<void*>(fn);
+    if (epoll_ctl(epoll_fd, EPOLL_CTL_ADD, fd, &ev) == -1) {
+        ERROR("epoll_ctl failed: %s\n", strerror(errno));
+    }
+}
+
 void service::NotifyStateChange(const char* new_state) {
     if (!properties_initialized()) {
         // If properties aren't available yet, we can't set them.
@@ -1037,7 +1048,13 @@ int main(int argc, char** argv) {
     restorecon("/dev/__properties__");
     restorecon_recursive("/sys");
 
-    signal_init();
+    epoll_fd = epoll_create1(EPOLL_CLOEXEC);
+    if (epoll_fd == -1) {
+        ERROR("epoll_create1 failed: %s\n", strerror(errno));
+        exit(1);
+    }
+
+    signal_handler_init();
 
     property_load_boot_defaults();
     start_property_service();
@@ -1071,27 +1088,12 @@ int main(int argc, char** argv) {
     // Run all property triggers based on current state of the properties.
     queue_builtin_action(queue_property_triggers_action, "queue_property_triggers");
 
-    size_t fd_count = 0;
-    struct pollfd ufds[3];
-    ufds[fd_count++] = { .fd = get_signal_fd(), .events = POLLIN, .revents = 0 };
-    ufds[fd_count++] = { .fd = get_property_set_fd(), .events = POLLIN, .revents = 0 };
-    // TODO: can we work out when /dev/keychord is first accessible and open this fd then?
-    bool keychord_fd_init = false;
-
     while (true) {
         if (!waiting_for_exec) {
             execute_one_command();
             restart_processes();
         }
 
-        if (!keychord_fd_init && get_keychord_fd() > 0) {
-            ufds[fd_count].fd = get_keychord_fd();
-            ufds[fd_count].events = POLLIN;
-            ufds[fd_count].revents = 0;
-            fd_count++;
-            keychord_fd_init = true;
-        }
-
         int timeout = -1;
         if (process_needs_restart) {
             timeout = (process_needs_restart - gettime()) * 1000;
@@ -1105,24 +1107,12 @@ int main(int argc, char** argv) {
 
         bootchart_sample(&timeout);
 
-        int nr = TEMP_FAILURE_RETRY(poll(ufds, fd_count, timeout));
-        if (nr <= 0) {
-            if (nr == -1) {
-                ERROR("poll failed: %s\n", strerror(errno));
-            }
-            continue;
-        }
-
-        for (size_t i = 0; i < fd_count; i++) {
-            if (ufds[i].revents & POLLIN) {
-                if (ufds[i].fd == get_property_set_fd()) {
-                    handle_property_set_fd();
-                } else if (ufds[i].fd == get_keychord_fd()) {
-                    handle_keychord();
-                } else if (ufds[i].fd == get_signal_fd()) {
-                    handle_signal();
-                }
-            }
+        epoll_event ev;
+        int nr = TEMP_FAILURE_RETRY(epoll_wait(epoll_fd, &ev, 1, timeout));
+        if (nr == -1) {
+            ERROR("epoll_wait failed: %s\n", strerror(errno));
+        } else if (nr == 1) {
+            ((void (*)()) ev.data.ptr)();
         }
     }
 
diff --git a/init/init.h b/init/init.h
index a104af6..1cabb14 100644
--- a/init/init.h
+++ b/init/init.h
@@ -155,4 +155,6 @@ int selinux_reload_policy(void);
 
 void zap_stdio(void);
 
+void register_epoll_handler(int fd, void (*fn)());
+
 #endif	/* _INIT_INIT_H */
diff --git a/init/keychords.cpp b/init/keychords.cpp
index 27894a2..10d9573 100644
--- a/init/keychords.cpp
+++ b/init/keychords.cpp
@@ -62,37 +62,7 @@ void add_service_keycodes(struct service *svc)
     }
 }
 
-void keychord_init()
-{
-    int fd, ret;
-
-    service_for_each(add_service_keycodes);
-
-    /* nothing to do if no services require keychords */
-    if (!keychords)
-        return;
-
-    fd = open("/dev/keychord", O_RDWR | O_CLOEXEC);
-    if (fd < 0) {
-        ERROR("could not open /dev/keychord\n");
-        return;
-    }
-
-    ret = write(fd, keychords, keychords_length);
-    if (ret != keychords_length) {
-        ERROR("could not configure /dev/keychord %d: %s\n", ret, strerror(errno));
-        close(fd);
-        fd = -1;
-    }
-
-    free(keychords);
-    keychords = 0;
-
-    keychord_fd = fd;
-}
-
-void handle_keychord()
-{
+static void handle_keychord() {
     struct service *svc;
     char adb_enabled[PROP_VALUE_MAX];
     int ret;
@@ -117,7 +87,28 @@ void handle_keychord()
     }
 }
 
-int get_keychord_fd()
-{
-    return keychord_fd;
+void keychord_init() {
+    service_for_each(add_service_keycodes);
+
+    // Nothing to do if no services require keychords.
+    if (!keychords) {
+        return;
+    }
+
+    keychord_fd = TEMP_FAILURE_RETRY(open("/dev/keychord", O_RDWR | O_CLOEXEC));
+    if (keychord_fd == -1) {
+        ERROR("could not open /dev/keychord: %s\n", strerror(errno));
+        return;
+    }
+
+    int ret = write(keychord_fd, keychords, keychords_length);
+    if (ret != keychords_length) {
+        ERROR("could not configure /dev/keychord %d: %s\n", ret, strerror(errno));
+        close(keychord_fd);
+    }
+
+    free(keychords);
+    keychords = nullptr;
+
+    register_epoll_handler(keychord_fd, handle_keychord);
 }
diff --git a/init/keychords.h b/init/keychords.h
index 070b858..d2723b7 100644
--- a/init/keychords.h
+++ b/init/keychords.h
@@ -19,9 +19,7 @@
 
 struct service;
 
-void add_service_keycodes(struct service *svc);
-void keychord_init(void);
-void handle_keychord(void);
-int get_keychord_fd(void);
+void add_service_keycodes(service*);
+void keychord_init();
 
 #endif
diff --git a/init/property_service.cpp b/init/property_service.cpp
index 94c5fd9..930ef82 100644
--- a/init/property_service.cpp
+++ b/init/property_service.cpp
@@ -246,7 +246,7 @@ int property_set(const char* name, const char* value) {
     return rc;
 }
 
-void handle_property_set_fd()
+static void handle_property_set_fd()
 {
     prop_msg msg;
     int s;
@@ -527,8 +527,6 @@ void start_property_service() {
     }
 
     listen(property_set_fd, 8);
-}
 
-int get_property_set_fd() {
-    return property_set_fd;
+    register_epoll_handler(property_set_fd, handle_property_set_fd);
 }
diff --git a/init/property_service.h b/init/property_service.h
index 825a7dd..a27053d 100644
--- a/init/property_service.h
+++ b/init/property_service.h
@@ -20,7 +20,6 @@
 #include <stddef.h>
 #include <sys/system_properties.h>
 
-extern void handle_property_set_fd(void);
 extern void property_init(void);
 extern void property_load_boot_defaults(void);
 extern void load_persist_props(void);
@@ -30,7 +29,6 @@ void get_property_workspace(int *fd, int *sz);
 extern int __property_get(const char *name, char *value);
 extern int property_set(const char *name, const char *value);
 extern bool properties_initialized();
-int get_property_set_fd(void);
 
 #ifndef __clang__
 extern void __property_get_size_error()
diff --git a/init/signal_handler.cpp b/init/signal_handler.cpp
index 37d21bc..39a466d 100644
--- a/init/signal_handler.cpp
+++ b/init/signal_handler.cpp
@@ -147,7 +147,7 @@ static void reap_any_outstanding_children() {
     }
 }
 
-void handle_signal() {
+static void handle_signal() {
     // Clear outstanding requests.
     char buf[32];
     read(signal_read_fd, buf, sizeof(buf));
@@ -161,7 +161,7 @@ static void SIGCHLD_handler(int) {
     }
 }
 
-void signal_init() {
+void signal_handler_init() {
     // Create a signalling mechanism for SIGCHLD.
     int s[2];
     if (socketpair(AF_UNIX, SOCK_STREAM | SOCK_NONBLOCK | SOCK_CLOEXEC, 0, s) == -1) {
@@ -180,8 +180,6 @@ void signal_init() {
     sigaction(SIGCHLD, &act, 0);
 
     reap_any_outstanding_children();
-}
 
-int get_signal_fd() {
-    return signal_read_fd;
+    register_epoll_handler(signal_read_fd, handle_signal);
 }
diff --git a/init/signal_handler.h b/init/signal_handler.h
index b092ccb..449b4af 100644
--- a/init/signal_handler.h
+++ b/init/signal_handler.h
@@ -17,8 +17,6 @@
 #ifndef _INIT_SIGNAL_HANDLER_H_
 #define _INIT_SIGNAL_HANDLER_H_
 
-void signal_init(void);
-void handle_signal(void);
-int get_signal_fd(void);
+void signal_handler_init(void);
 
 #endif