cutils: Add support for ioprio cgroup

include/cutils/iosched_policy.h

@@ -31,6 +31,8 @@ typedef enum {
 extern int android_set_ioprio(int pid, IoSchedClass clazz, int ioprio);
 extern int android_get_ioprio(int pid, IoSchedClass *clazz, int *ioprio);
 
+extern int android_set_rt_ioprio(int pid, int rt);
+
 #ifdef __cplusplus
 }
 #endif

libcutils/iosched_policy.c

@@ -1,9 +1,10 @@
 /*
-** Copyright 2007, The Android Open Source Project
+** Copyright 2007-2014, The Android Open Source Project
+** Copyright 2015, The CyanogenMod Project
 **
-** Licensed under the Apache License, Version 2.0 (the "License"); 
-** you may not use this file except in compliance with the License. 
-** You may obtain a copy of the License at 
+** Licensed under the Apache License, Version 2.0 (the "License");
+** you may not use this file except in compliance with the License.
+** You may obtain a copy of the License at
 **
 **     http://www.apache.org/licenses/LICENSE-2.0 
 **
@@ -20,28 +21,30 @@
 #include <stdlib.h>
 #include <string.h>
 #include <unistd.h>
+#include <pthread.h>
 
 #include <cutils/iosched_policy.h>
+#define LOG_TAG "iosched_policy"
+#include <cutils/log.h>
+
+#define __android_unused __attribute__((__unused__))
 
 #ifdef HAVE_ANDROID_OS
 #include <linux/ioprio.h>
 #include <sys/syscall.h>
-#define __android_unused
-#else
-#define __android_unused __attribute__((__unused__))
-#endif
+#include <sys/stat.h>
+
+static int __rtio_cgroup_supported = -1;
+static pthread_once_t __rtio_init_once = PTHREAD_ONCE_INIT;
 
 int android_set_ioprio(int pid __android_unused, IoSchedClass clazz __android_unused, int ioprio __android_unused) {
-#ifdef HAVE_ANDROID_OS
     if (syscall(SYS_ioprio_set, IOPRIO_WHO_PROCESS, pid, ioprio | (clazz << IOPRIO_CLASS_SHIFT))) {
         return -1;
     }
-#endif
     return 0;
 }
 
 int android_get_ioprio(int pid __android_unused, IoSchedClass *clazz, int *ioprio) {
-#ifdef HAVE_ANDROID_OS
     int rc;
 
     if ((rc = syscall(SYS_ioprio_get, IOPRIO_WHO_PROCESS, pid)) < 0) {
@@ -50,9 +53,83 @@ int android_get_ioprio(int pid __android_unused, IoSchedClass *clazz, int *iopri
 
     *clazz = (rc >> IOPRIO_CLASS_SHIFT);
     *ioprio = (rc & 0xff);
+    return 0;
+}
+
+static void __initialize_rtio(void) {
+    if (!access("/sys/fs/cgroup/bfqio/tasks", W_OK) ||
+        !access("/sys/fs/cgroup/bfqio/rt-display/tasks", W_OK)) {
+        __rtio_cgroup_supported = 1;
+    } else {
+        __rtio_cgroup_supported = 0;
+    }
+}
+
+int android_set_rt_ioprio(int tid, int rt) {
+    int fd = -1, rc = -1;
+
+    pthread_once(&__rtio_init_once, __initialize_rtio);
+    if (__rtio_cgroup_supported != 1) {
+        return -1;
+    }
+
+    if (rt) {
+        fd = open("/sys/fs/cgroup/bfqio/rt-display/tasks", O_WRONLY | O_CLOEXEC);
+    } else {
+        fd = open("/sys/fs/cgroup/bfqio/tasks", O_WRONLY | O_CLOEXEC);
+    }
+
+    if (fd < 0) {
+        return -1;
+    }
+
+#ifdef HAVE_GETTID
+    if (tid == 0) {
+        tid = gettid();
+    }
+#endif
+
+    // specialized itoa -- works for tid > 0
+    char text[22];
+    char *end = text + sizeof(text) - 1;
+    char *ptr = end;
+    *ptr = '\0';
+    while (tid > 0) {
+        *--ptr = '0' + (tid % 10);
+        tid = tid / 10;
+    }
+
+    rc = write(fd, ptr, end - ptr);
+    if (rc < 0) {
+        /*
+         * If the thread is in the process of exiting,
+         * don't flag an error
+         */
+        if (errno == ESRCH) {
+            rc = 0;
+        } else {
+            SLOGV("android_set_rt_ioprio failed to write '%s' (%s); fd=%d\n",
+                  ptr, strerror(errno), fd);
+        }
+    }
+
+    close(fd);
+    return rc;
+}
+
 #else
+int android_set_ioprio(int pid __android_unused, IoSchedClass clazz __android_unused, int ioprio __android_unused) {
+    return 0;
+}
+
+int android_get_ioprio(int pid __android_unused, IoSchedClass *clazz, int *ioprio) {
     *clazz = IoSchedClass_NONE;
     *ioprio = 0;
-#endif
     return 0;
 }
+
+int android_set_rt_ioprio(int tid __android_unused, int rt __android_unused)
+{
+    return 0;
+}
+#endif