Removed cpusets/schedboost build time dependency.

These two Soong product_variables were usually controlled by
ENABLE_CPUSETS and ENABLE_SCHEDBOOST in BoardConfig.mk. This change
turns the build time variables into runtime decision by checking if
a special file, "tasks", can be found under the mount points,
/dev/cpuset and /dev/stune, for cpusets and schedboost, respectively.

That special file only exists when the corresponding Linux kernel
configurations, CONFIG_CPUSETS and CONFIG_SCHEDTUNE, are set.

Bug: 34726944

Test: Tested on Sailfish with following configurations
          neither cpuset nor schedtune enabled in the kernel
          cpuset enabled, but schedtune disabled in the kernel
          both cpuset and schedtune enabled in the kernel

Change-Id: I6695b8b32b2fecb4fd995018418bbe2edc5d590f

3 files changed, 126 insertions, 74 deletions

diff --git a/libcutils/Android.bp b/libcutils/Android.bp
index 8ba7452ef..cf3119590 100644
--- a/libcutils/Android.bp
+++ b/libcutils/Android.bp
@@ -60,7 +60,7 @@ cc_library {
         "native_handle.c",
         "open_memstream.c",
         "record_stream.c",
-        "sched_policy.c",
+        "sched_policy.cpp",
         "sockets.cpp",
         "strdup16to8.c",
         "strdup8to16.c",
@@ -141,14 +141,6 @@ cc_library {
     header_libs: ["libcutils_headers"],
     export_header_lib_headers: ["libcutils_headers"],
 
-    product_variables: {
-        cpusets: {
-            cflags: ["-DUSE_CPUSETS"],
-        },
-        schedboost: {
-            cflags: ["-DUSE_SCHEDBOOST"],
-        },
-    },
     cflags: [
         "-Werror",
         "-Wall",
diff --git a/libcutils/include/cutils/sched_policy.h b/libcutils/include/cutils/sched_policy.h
index 591bd4478..15391d981 100644
--- a/libcutils/include/cutils/sched_policy.h
+++ b/libcutils/include/cutils/sched_policy.h
@@ -17,10 +17,27 @@
 #ifndef __CUTILS_SCHED_POLICY_H
 #define __CUTILS_SCHED_POLICY_H
 
+#include <stdbool.h>
+
 #ifdef __cplusplus
 extern "C" {
 #endif
 
+/*
+ * Check if Linux kernel enables CPUSETS feature.
+ *
+ * Return value: 1 if Linux kernel CONFIG_CPUSETS=y; 0 otherwise.
+ */
+extern bool cpusets_enabled();
+
+/*
+ * Check if Linux kernel enables SCHEDTUNE feature (only available in Android
+ * common kernel or Linaro LSK, not in mainline Linux as of v4.9)
+ *
+ * Return value: 1 if Linux kernel CONFIG_SCHEDTUNE=y; 0 otherwise.
+ */
+extern bool schedboost_enabled();
+
 /* Keep in sync with THREAD_GROUP_* in frameworks/base/core/java/android/os/Process.java */
 typedef enum {
     SP_DEFAULT    = -1,
diff --git a/libcutils/sched_policy.c b/libcutils/sched_policy.cpp
index 5c5f3a563..7e3ad593e 100644
--- a/libcutils/sched_policy.c
+++ b/libcutils/sched_policy.cpp
@@ -58,13 +58,11 @@ static int __sys_supports_timerslack = -1;
 static int bg_cgroup_fd = -1;
 static int fg_cgroup_fd = -1;
 
-#ifdef USE_CPUSETS
 // File descriptors open to /dev/cpuset/../tasks, setup by initialize, or -1 on error
 static int system_bg_cpuset_fd = -1;
 static int bg_cpuset_fd = -1;
 static int fg_cpuset_fd = -1;
 static int ta_cpuset_fd = -1; // special cpuset for top app
-#endif
 
 // File descriptors open to /dev/stune/../tasks, setup by initialize, or -1 on error
 static int bg_schedboost_fd = -1;
@@ -106,8 +104,53 @@ static int add_tid_to_cgroup(int tid, int fd)
     return 0;
 }
 
-static void __initialize(void) {
-    char* filename;
+/*
+    If CONFIG_CPUSETS for Linux kernel is set, "tasks" can be found under
+    /dev/cpuset mounted in init.rc; otherwise, that file does not exist
+    even though the directory, /dev/cpuset, is still created (by init.rc).
+
+    A couple of other candidates (under cpuset mount directory):
+        notify_on_release
+        release_agent
+
+    Yet another way to decide if cpuset is enabled is to parse
+    /proc/self/status and search for lines begin with "Mems_allowed".
+
+    If CONFIG_PROC_PID_CPUSET is set, the existence "/proc/self/cpuset" can
+    be used to decide if CONFIG_CPUSETS is set, so we don't have a dependency
+    on where init.rc mounts cpuset. That's why we'd better require this
+    configuration be set if CONFIG_CPUSETS is set.
+
+    With runtime check using the following function, build time
+    variables like ENABLE_CPUSETS (used in Android.mk) or cpusets (used
+    in Android.bp) are not needed.
+ */
+
+bool cpusets_enabled() {
+    static bool enabled = (access("/dev/cpuset/tasks", F_OK) == 0);
+
+    return enabled;
+}
+
+/*
+    Similar to CONFIG_CPUSETS above, but with a different configuration
+    CONFIG_SCHEDTUNE that's in Android common Linux kernel and Linaro
+    Stable Kernel (LSK), but not in mainline Linux as of v4.9.
+
+    With runtime check using the following function, build time
+    variables like ENABLE_SCHEDBOOST (used in Android.mk) or schedboost
+    (used in Android.bp) are not needed.
+
+ */
+
+bool schedboost_enabled() {
+    static bool enabled = (access("/dev/stune/tasks", F_OK) == 0);
+
+    return enabled;
+}
+
+static void __initialize() {
+    const char* filename;
     if (!access("/dev/cpuctl/tasks", W_OK)) {
         __sys_supports_schedgroups = 1;
 
@@ -126,28 +169,28 @@ static void __initialize(void) {
         __sys_supports_schedgroups = 0;
     }
 
-#ifdef USE_CPUSETS
-    if (!access("/dev/cpuset/tasks", W_OK)) {
-
-        filename = "/dev/cpuset/foreground/tasks";
-        fg_cpuset_fd = open(filename, O_WRONLY | O_CLOEXEC);
-        filename = "/dev/cpuset/background/tasks";
-        bg_cpuset_fd = open(filename, O_WRONLY | O_CLOEXEC);
-        filename = "/dev/cpuset/system-background/tasks";
-        system_bg_cpuset_fd = open(filename, O_WRONLY | O_CLOEXEC);
-        filename = "/dev/cpuset/top-app/tasks";
-        ta_cpuset_fd = open(filename, O_WRONLY | O_CLOEXEC);
-
-#ifdef USE_SCHEDBOOST
-        filename = "/dev/stune/top-app/tasks";
-        ta_schedboost_fd = open(filename, O_WRONLY | O_CLOEXEC);
-        filename = "/dev/stune/foreground/tasks";
-        fg_schedboost_fd = open(filename, O_WRONLY | O_CLOEXEC);
-        filename = "/dev/stune/background/tasks";
-        bg_schedboost_fd = open(filename, O_WRONLY | O_CLOEXEC);
-#endif
+    if (cpusets_enabled()) {
+        if (!access("/dev/cpuset/tasks", W_OK)) {
+
+            filename = "/dev/cpuset/foreground/tasks";
+            fg_cpuset_fd = open(filename, O_WRONLY | O_CLOEXEC);
+            filename = "/dev/cpuset/background/tasks";
+            bg_cpuset_fd = open(filename, O_WRONLY | O_CLOEXEC);
+            filename = "/dev/cpuset/system-background/tasks";
+            system_bg_cpuset_fd = open(filename, O_WRONLY | O_CLOEXEC);
+            filename = "/dev/cpuset/top-app/tasks";
+            ta_cpuset_fd = open(filename, O_WRONLY | O_CLOEXEC);
+
+            if (schedboost_enabled()) {
+                filename = "/dev/stune/top-app/tasks";
+                ta_schedboost_fd = open(filename, O_WRONLY | O_CLOEXEC);
+                filename = "/dev/stune/foreground/tasks";
+                fg_schedboost_fd = open(filename, O_WRONLY | O_CLOEXEC);
+                filename = "/dev/stune/background/tasks";
+                bg_schedboost_fd = open(filename, O_WRONLY | O_CLOEXEC);
+            }
+        }
     }
-#endif
 
     char buf[64];
     snprintf(buf, sizeof(buf), "/proc/%d/timerslack_ns", getpid());
@@ -235,33 +278,34 @@ int get_sched_policy(int tid, SchedPolicy *policy)
 
     if (__sys_supports_schedgroups) {
         char grpBuf[32];
-#ifdef USE_CPUSETS
-        if (getCGroupSubsys(tid, "cpuset", grpBuf, sizeof(grpBuf)) < 0)
-            return -1;
-        if (grpBuf[0] == '\0') {
-            *policy = SP_FOREGROUND;
-        } else if (!strcmp(grpBuf, "foreground")) {
-            *policy = SP_FOREGROUND;
-        } else if (!strcmp(grpBuf, "background")) {
-            *policy = SP_BACKGROUND;
-        } else if (!strcmp(grpBuf, "top-app")) {
-            *policy = SP_TOP_APP;
-        } else {
-            errno = ERANGE;
-            return -1;
-        }
-#else
-        if (getCGroupSubsys(tid, "cpu", grpBuf, sizeof(grpBuf)) < 0)
-            return -1;
-        if (grpBuf[0] == '\0') {
-            *policy = SP_FOREGROUND;
-        } else if (!strcmp(grpBuf, "bg_non_interactive")) {
-            *policy = SP_BACKGROUND;
+
+        if (cpusets_enabled()) {
+            if (getCGroupSubsys(tid, "cpuset", grpBuf, sizeof(grpBuf)) < 0)
+                return -1;
+            if (grpBuf[0] == '\0') {
+                *policy = SP_FOREGROUND;
+            } else if (!strcmp(grpBuf, "foreground")) {
+                *policy = SP_FOREGROUND;
+            } else if (!strcmp(grpBuf, "background")) {
+                *policy = SP_BACKGROUND;
+            } else if (!strcmp(grpBuf, "top-app")) {
+                *policy = SP_TOP_APP;
+            } else {
+                errno = ERANGE;
+                return -1;
+            }
         } else {
-            errno = ERANGE;
-            return -1;
+            if (getCGroupSubsys(tid, "cpu", grpBuf, sizeof(grpBuf)) < 0)
+                return -1;
+            if (grpBuf[0] == '\0') {
+                *policy = SP_FOREGROUND;
+            } else if (!strcmp(grpBuf, "bg_non_interactive")) {
+                *policy = SP_BACKGROUND;
+            } else {
+                errno = ERANGE;
+                return -1;
+            }
         }
-#endif
     } else {
         int rc = sched_getscheduler(tid);
         if (rc < 0)
@@ -281,9 +325,10 @@ int get_sched_policy(int tid, SchedPolicy *policy)
 int set_cpuset_policy(int tid, SchedPolicy policy)
 {
     // in the absence of cpusets, use the old sched policy
-#ifndef USE_CPUSETS
-    return set_sched_policy(tid, policy);
-#else
+    if (!cpusets_enabled()) {
+        return set_sched_policy(tid, policy);
+    }
+
     if (tid == 0) {
         tid = gettid();
     }
@@ -320,15 +365,14 @@ int set_cpuset_policy(int tid, SchedPolicy policy)
             return -errno;
     }
 
-#ifdef USE_SCHEDBOOST
-    if (boost_fd > 0 && add_tid_to_cgroup(tid, boost_fd) != 0) {
-        if (errno != ESRCH && errno != ENOENT)
-            return -errno;
+    if (schedboost_enabled()) {
+        if (boost_fd > 0 && add_tid_to_cgroup(tid, boost_fd) != 0) {
+            if (errno != ESRCH && errno != ENOENT)
+                return -errno;
+        }
     }
-#endif
 
     return 0;
-#endif
 }
 
 static void set_timerslack_ns(int tid, unsigned long long slack) {
@@ -420,18 +464,17 @@ int set_sched_policy(int tid, SchedPolicy policy)
             break;
         }
 
-
         if (add_tid_to_cgroup(tid, fd) != 0) {
             if (errno != ESRCH && errno != ENOENT)
                 return -errno;
         }
 
-#ifdef USE_SCHEDBOOST
-        if (boost_fd > 0 && add_tid_to_cgroup(tid, boost_fd) != 0) {
-            if (errno != ESRCH && errno != ENOENT)
-                return -errno;
+        if (schedboost_enabled()) {
+            if (boost_fd > 0 && add_tid_to_cgroup(tid, boost_fd) != 0) {
+                if (errno != ESRCH && errno != ENOENT)
+                    return -errno;
+            }
         }
-#endif
     } else {
         struct sched_param param;