diff --git a/fastboot/fastboot.cpp b/fastboot/fastboot.cpp
index 7f4a0dd..3f8bc8f 100644
--- a/fastboot/fastboot.cpp
+++ b/fastboot/fastboot.cpp
@@ -1742,6 +1742,14 @@
         } else if(!strcmp(*argv, "set_active")) {
             require(2);
             std::string slot = verify_slot(transport, std::string(argv[1]), false);
+            // Legacy support: verify_slot() removes leading underscores, we need to put them back
+            // in for old bootloaders. Legacy bootloaders do not have the slot-count variable but
+            // do have slot-suffixes.
+            std::string var;
+            if (!fb_getvar(transport, "slot-count", &var) &&
+                    fb_getvar(transport, "slot-suffixes", &var)) {
+                slot = "_" + slot;
+            }
             fb_set_active(slot.c_str());
             skip(2);
         } else if(!strcmp(*argv, "oem")) {
diff --git a/init/bootchart.cpp b/init/bootchart.cpp
index 8fb55f0..7a8a3d5 100644
--- a/init/bootchart.cpp
+++ b/init/bootchart.cpp
@@ -34,29 +34,25 @@
 #include <vector>
 
 #include <android-base/file.h>
+#include <android-base/stringprintf.h>
 
-#define LOG_ROOT        "/data/bootchart"
-#define LOG_STAT        LOG_ROOT"/proc_stat.log"
-#define LOG_PROCS       LOG_ROOT"/proc_ps.log"
-#define LOG_DISK        LOG_ROOT"/proc_diskstats.log"
-#define LOG_HEADER      LOG_ROOT"/header"
-#define LOG_ACCT        LOG_ROOT"/kernel_pacct"
+using android::base::StringPrintf;
 
-#define LOG_STARTFILE   LOG_ROOT"/start"
-#define LOG_STOPFILE    LOG_ROOT"/stop"
+static constexpr const char* LOG_STAT = "/data/bootchart/proc_stat.log";
+static constexpr const char* LOG_PROC = "/data/bootchart/proc_ps.log";
+static constexpr const char* LOG_DISK = "/data/bootchart/proc_diskstats.log";
+static constexpr const char* LOG_HEADER = "/data/bootchart/header";
 
 // Polling period in ms.
-static const int BOOTCHART_POLLING_MS = 200;
-
-// Max polling time in seconds.
-static const int BOOTCHART_MAX_TIME_SEC = 10*60;
+static constexpr int BOOTCHART_POLLING_MS = 200;
 
 static long long g_last_bootchart_time;
-static int g_remaining_samples;
 
-static FILE* log_stat;
-static FILE* log_procs;
-static FILE* log_disks;
+static bool g_bootcharting = false;
+
+static FILE* g_stat_log;
+static FILE* g_proc_log;
+static FILE* g_disk_log;
 
 static long long get_uptime_jiffies() {
     std::string uptime;
@@ -99,12 +95,12 @@
     fclose(out);
 }
 
-static void do_log_uptime(FILE* log) {
+static void log_uptime(FILE* log) {
     fprintf(log, "%lld\n", get_uptime_jiffies());
 }
 
-static void do_log_file(FILE* log, const char* procfile) {
-    do_log_uptime(log);
+static void log_file(FILE* log, const char* procfile) {
+    log_uptime(log);
 
     std::string content;
     if (android::base::ReadFileToString(procfile, &content)) {
@@ -112,161 +108,115 @@
     }
 }
 
-static void do_log_procs(FILE* log) {
-    do_log_uptime(log);
+static void log_processes() {
+    log_uptime(g_proc_log);
 
     std::unique_ptr<DIR, int(*)(DIR*)> dir(opendir("/proc"), closedir);
     struct dirent* entry;
     while ((entry = readdir(dir.get())) != NULL) {
         // Only match numeric values.
-        char* end;
-        int pid = strtol(entry->d_name, &end, 10);
-        if (end != NULL && end > entry->d_name && *end == 0) {
-            char filename[32];
+        int pid = atoi(entry->d_name);
+        if (pid == 0) continue;
 
-            // /proc/<pid>/stat only has truncated task names, so get the full
-            // name from /proc/<pid>/cmdline.
-            snprintf(filename, sizeof(filename), "/proc/%d/cmdline", pid);
-            std::string cmdline;
-            android::base::ReadFileToString(filename, &cmdline);
-            const char* full_name = cmdline.c_str(); // So we stop at the first NUL.
-
-            // Read process stat line.
-            snprintf(filename, sizeof(filename), "/proc/%d/stat", pid);
-            std::string stat;
-            if (android::base::ReadFileToString(filename, &stat)) {
-                if (!cmdline.empty()) {
-                    // Substitute the process name with its real name.
-                    size_t open = stat.find('(');
-                    size_t close = stat.find_last_of(')');
-                    if (open != std::string::npos && close != std::string::npos) {
-                        stat.replace(open + 1, close - open - 1, full_name);
-                    }
-                }
-                fputs(stat.c_str(), log);
-            }
-        }
-    }
-
-    fputc('\n', log);
-}
-
-static int bootchart_init() {
-    int timeout = 0;
-
-    std::string start;
-    android::base::ReadFileToString(LOG_STARTFILE, &start);
-    if (!start.empty()) {
-        timeout = atoi(start.c_str());
-    } else {
-        // When running with emulator, androidboot.bootchart=<timeout>
-        // might be passed by as kernel parameters to specify the bootchart
-        // timeout. this is useful when using -wipe-data since the /data
-        // partition is fresh.
+        // /proc/<pid>/stat only has truncated task names, so get the full
+        // name from /proc/<pid>/cmdline.
         std::string cmdline;
-        const char* s;
-        android::base::ReadFileToString("/proc/cmdline", &cmdline);
-#define KERNEL_OPTION  "androidboot.bootchart="
-        if ((s = strstr(cmdline.c_str(), KERNEL_OPTION)) != NULL) {
-            timeout = atoi(s + sizeof(KERNEL_OPTION) - 1);
+        android::base::ReadFileToString(StringPrintf("/proc/%d/cmdline", pid), &cmdline);
+        const char* full_name = cmdline.c_str(); // So we stop at the first NUL.
+
+        // Read process stat line.
+        std::string stat;
+        if (android::base::ReadFileToString(StringPrintf("/proc/%d/stat", pid), &stat)) {
+            if (!cmdline.empty()) {
+                // Substitute the process name with its real name.
+                size_t open = stat.find('(');
+                size_t close = stat.find_last_of(')');
+                if (open != std::string::npos && close != std::string::npos) {
+                    stat.replace(open + 1, close - open - 1, full_name);
+                }
+            }
+            fputs(stat.c_str(), g_proc_log);
         }
     }
-    if (timeout == 0)
+
+    fputc('\n', g_proc_log);
+}
+
+static int do_bootchart_start() {
+    // We don't care about the content, but we do care that /data/bootchart/enabled actually exists.
+    std::string start;
+    if (!android::base::ReadFileToString("/data/bootchart/enabled", &start)) {
+        LOG(VERBOSE) << "Not bootcharting";
         return 0;
+    }
 
-    if (timeout > BOOTCHART_MAX_TIME_SEC)
-        timeout = BOOTCHART_MAX_TIME_SEC;
-
-    int count = (timeout*1000 + BOOTCHART_POLLING_MS-1)/BOOTCHART_POLLING_MS;
-
-    log_stat = fopen(LOG_STAT, "we");
-    if (log_stat == NULL) {
+    // Open log files.
+    std::unique_ptr<FILE, decltype(&fclose)> stat_log(fopen(LOG_STAT, "we"), fclose);
+    if (!stat_log) {
+        PLOG(ERROR) << "Bootcharting couldn't open " << LOG_STAT;
         return -1;
     }
-    log_procs = fopen(LOG_PROCS, "we");
-    if (log_procs == NULL) {
-        fclose(log_stat);
+    std::unique_ptr<FILE, decltype(&fclose)> proc_log(fopen(LOG_PROC, "we"), fclose);
+    if (!proc_log) {
+        PLOG(ERROR) << "Bootcharting couldn't open " << LOG_PROC;
         return -1;
     }
-    log_disks = fopen(LOG_DISK, "we");
-    if (log_disks == NULL) {
-        fclose(log_stat);
-        fclose(log_procs);
+    std::unique_ptr<FILE, decltype(&fclose)> disk_log(fopen(LOG_DISK, "we"), fclose);
+    if (!disk_log) {
+        PLOG(ERROR) << "Bootcharting couldn't open " << LOG_DISK;
         return -1;
     }
 
-    // Create kernel process accounting file.
-    close(open(LOG_ACCT, O_WRONLY | O_CREAT | O_TRUNC | O_CLOEXEC, 0644));
-    acct(LOG_ACCT);
-
+    LOG(INFO) << "Bootcharting started";
+    g_stat_log = stat_log.release();
+    g_proc_log = proc_log.release();
+    g_disk_log = disk_log.release();
+    g_bootcharting = true;
     log_header();
-    return count;
-}
-
-int do_bootchart_init(const std::vector<std::string>& args) {
-    g_remaining_samples = bootchart_init();
-    if (g_remaining_samples < 0) {
-        PLOG(ERROR) << "Bootcharting initialization failed";
-    } else if (g_remaining_samples > 0) {
-        LOG(INFO) << "Bootcharting started (will run for "
-                  << ((g_remaining_samples * BOOTCHART_POLLING_MS) / 1000) << " s).";
-    } else {
-        LOG(VERBOSE) << "Not bootcharting.";
-    }
-    return 0;
-}
-
-static int bootchart_step() {
-    do_log_file(log_stat,   "/proc/stat");
-    do_log_file(log_disks,  "/proc/diskstats");
-    do_log_procs(log_procs);
-
-    // Stop if /data/bootchart/stop contains 1.
-    std::string stop;
-    if (android::base::ReadFileToString(LOG_STOPFILE, &stop) && stop == "1") {
-        return -1;
-    }
 
     return 0;
 }
 
-/* called to get time (in ms) used by bootchart */
-static long long bootchart_gettime() {
-    return 10LL*get_uptime_jiffies();
+static void do_bootchart_step() {
+    log_file(g_stat_log, "/proc/stat");
+    log_file(g_disk_log, "/proc/diskstats");
+    log_processes();
 }
 
-static void bootchart_finish() {
-    unlink(LOG_STOPFILE);
-    fclose(log_stat);
-    fclose(log_disks);
-    fclose(log_procs);
-    acct(NULL);
+static int do_bootchart_stop() {
+    if (!g_bootcharting) return 0;
+
     LOG(INFO) << "Bootcharting finished";
+    g_bootcharting = false;
+    fclose(g_stat_log);
+    fclose(g_disk_log);
+    fclose(g_proc_log);
+    return 0;
+}
+
+int do_bootchart(const std::vector<std::string>& args) {
+    if (args[1] == "start") return do_bootchart_start();
+    return do_bootchart_stop();
 }
 
 void bootchart_sample(int* timeout) {
     // Do we have any more bootcharting to do?
-    if (g_remaining_samples <= 0) {
-        return;
-    }
+    if (!g_bootcharting) return;
 
-    long long current_time = bootchart_gettime();
+    long long current_time = 10LL * get_uptime_jiffies();
     int elapsed_time = current_time - g_last_bootchart_time;
 
     if (elapsed_time >= BOOTCHART_POLLING_MS) {
-        // Count missed samples.
         while (elapsed_time >= BOOTCHART_POLLING_MS) {
             elapsed_time -= BOOTCHART_POLLING_MS;
-            g_remaining_samples--;
         }
-        // Count may be negative, take a sample anyway.
+
         g_last_bootchart_time = current_time;
-        if (bootchart_step() < 0 || g_remaining_samples <= 0) {
-            bootchart_finish();
-            g_remaining_samples = 0;
-        }
+        do_bootchart_step();
     }
-    if (g_remaining_samples > 0) {
+
+    // Schedule another?
+    if (g_bootcharting) {
         int remaining_time = BOOTCHART_POLLING_MS - elapsed_time;
         if (*timeout < 0 || *timeout > remaining_time) {
             *timeout = remaining_time;
diff --git a/init/bootchart.h b/init/bootchart.h
index 47eda7a..1e8d0f8 100644
--- a/init/bootchart.h
+++ b/init/bootchart.h
@@ -20,7 +20,7 @@
 #include <string>
 #include <vector>
 
-int do_bootchart_init(const std::vector<std::string>& args);
+int do_bootchart(const std::vector<std::string>& args);
 void bootchart_sample(int* timeout);
 
 #endif /* _BOOTCHART_H */
diff --git a/init/builtins.cpp b/init/builtins.cpp
index cf8b274..812ac3c 100644
--- a/init/builtins.cpp
+++ b/init/builtins.cpp
@@ -1028,7 +1028,7 @@
 BuiltinFunctionMap::Map& BuiltinFunctionMap::map() const {
     constexpr std::size_t kMax = std::numeric_limits<std::size_t>::max();
     static const Map builtin_functions = {
-        {"bootchart_init",          {0,     0,    do_bootchart_init}},
+        {"bootchart",               {1,     1,    do_bootchart}},
         {"chmod",                   {2,     2,    do_chmod}},
         {"chown",                   {2,     3,    do_chown}},
         {"class_reset",             {1,     1,    do_class_reset}},
diff --git a/init/grab-bootchart.sh b/init/grab-bootchart.sh
index d6082aa..c4ff6df 100755
--- a/init/grab-bootchart.sh
+++ b/init/grab-bootchart.sh
@@ -11,7 +11,7 @@
 LOGROOT=/data/bootchart
 TARBALL=bootchart.tgz
 
-FILES="header proc_stat.log proc_ps.log proc_diskstats.log kernel_pacct"
+FILES="header proc_stat.log proc_ps.log proc_diskstats.log"
 
 for f in $FILES; do
     adb "${@}" pull $LOGROOT/$f $TMPDIR/$f 2>&1 > /dev/null
diff --git a/init/readme.txt b/init/readme.txt
index 6f40d6b..530b392 100644
--- a/init/readme.txt
+++ b/init/readme.txt
@@ -253,9 +253,10 @@
 Commands
 --------
 
-bootchart_init
-   Start bootcharting if configured (see below).
-   This is included in the default init.rc.
+bootchart [start|stop]
+   Start/stop bootcharting. These are present in the default init.rc files,
+   but bootcharting is only active if the file /data/bootchart/enabled exists;
+   otherwise bootchart start/stop are no-ops.
 
 chmod <octal-mode> <path>
    Change file access permissions.
@@ -471,19 +472,11 @@
 On the emulator, use the -bootchart <timeout> option to boot with bootcharting
 activated for <timeout> seconds.
 
-On a device, create /data/bootchart/start with a command like the following:
+On a device:
 
-  adb shell 'echo $TIMEOUT > /data/bootchart/start'
+  adb shell 'touch /data/bootchart/enabled'
 
-Where the value of $TIMEOUT corresponds to the desired bootcharted period in
-seconds. Bootcharting will stop after that many seconds have elapsed.
-You can also stop the bootcharting at any moment by doing the following:
-
-  adb shell 'echo 1 > /data/bootchart/stop'
-
-Note that /data/bootchart/stop is deleted automatically by init at the end of
-the bootcharting. This is not the case with /data/bootchart/start, so don't
-forget to delete it when you're done collecting data.
+Don't forget to delete this file when you're done collecting data!
 
 The log files are written to /data/bootchart/. A script is provided to
 retrieve them and create a bootchart.tgz file that can be used with the
diff --git a/liblog/Android.bp b/liblog/Android.bp
index e59a460..2424dba 100644
--- a/liblog/Android.bp
+++ b/liblog/Android.bp
@@ -30,7 +30,7 @@
     "event_tag_map.cpp",
     "config_read.c",
     "log_time.cpp",
-    "log_is_loggable.c",
+    "properties.c",
     "logprint.c",
     "pmsg_reader.c",
     "pmsg_writer.c",
diff --git a/liblog/log_is_loggable.c b/liblog/properties.c
similarity index 100%
rename from liblog/log_is_loggable.c
rename to liblog/properties.c
diff --git a/rootdir/init.rc b/rootdir/init.rc
index 249b9e2..c0a0fce 100644
--- a/rootdir/init.rc
+++ b/rootdir/init.rc
@@ -366,7 +366,7 @@
     # Start bootcharting as soon as possible after the data partition is
     # mounted to collect more data.
     mkdir /data/bootchart 0755 shell shell
-    bootchart_init
+    bootchart start
 
     # Avoid predictable entropy pool. Carry over entropy from previous boot.
     copy /data/system/entropy.dat /dev/urandom
@@ -624,6 +624,9 @@
 on property:sys.powerctl=*
     powerctl ${sys.powerctl}
 
+on property:sys.boot_completed=1
+    bootchart stop
+
 # system server cannot write to /proc/sys files,
 # and chown/chmod does not work for /proc/sys/ entries.
 # So proxy writes through init.