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/* libs/cutils/sched_policy.c
**
** Copyright 2007, The Android Open Source 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
**
** http://www.apache.org/licenses/LICENSE-2.0
**
** Unless required by applicable law or agreed to in writing, software
** distributed under the License is distributed on an "AS IS" BASIS,
** WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
** See the License for the specific language governing permissions and
** limitations under the License.
*/
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <errno.h>
#include <fcntl.h>
#define LOG_TAG "SchedPolicy"
#include "cutils/log.h"
#ifdef HAVE_SCHED_H
#include <sched.h>
#include <cutils/sched_policy.h>
#ifndef SCHED_NORMAL
#define SCHED_NORMAL 0
#endif
#ifndef SCHED_BATCH
#define SCHED_BATCH 3
#endif
#define POLICY_DEBUG 0
static int __sys_supports_schedgroups = -1;
static int add_tid_to_cgroup(int tid, const char *grp_name)
{
int fd;
char path[255];
char text[64];
sprintf(path, "/dev/cpuctl/%s/tasks", grp_name);
if ((fd = open(path, O_WRONLY)) < 0) {
LOGE("add_tid_to_cgroup failed to open '%s' (%s)\n", path,
strerror(errno));
return -1;
}
sprintf(text, "%d", tid);
if (write(fd, text, strlen(text)) < 0) {
close(fd);
/*
* If the thread is in the process of exiting,
* don't flag an error
*/
if (errno == ESRCH)
return 0;
LOGW("add_tid_to_cgroup failed to write '%s' (%s)\n", path,
strerror(errno));
return -1;
}
close(fd);
return 0;
}
static inline void initialize()
{
if (__sys_supports_schedgroups < 0) {
if (!access("/dev/cpuctl/tasks", F_OK)) {
__sys_supports_schedgroups = 1;
} else {
__sys_supports_schedgroups = 0;
}
}
}
/*
* Try to get the scheduler group.
*
* The data from /proc/<pid>/cgroup looks like:
* 2:cpu:/bg_non_interactive
*
* We return the part after the "/", which will be an empty string for
* the default cgroup. If the string is longer than "bufLen", the string
* will be truncated.
*/
static int getSchedulerGroup(int tid, char* buf, size_t bufLen)
{
#ifdef HAVE_ANDROID_OS
char pathBuf[32];
char readBuf[256];
ssize_t count;
int fd;
snprintf(pathBuf, sizeof(pathBuf), "/proc/%d/cgroup", tid);
if ((fd = open(pathBuf, O_RDONLY)) < 0) {
return -1;
}
count = read(fd, readBuf, sizeof(readBuf));
if (count <= 0) {
close(fd);
errno = ENODATA;
return -1;
}
close(fd);
readBuf[--count] = '\0'; /* remove the '\n', now count==strlen */
char* cp = strchr(readBuf, '/');
if (cp == NULL) {
readBuf[sizeof(readBuf)-1] = '\0';
errno = ENODATA;
return -1;
}
memcpy(buf, cp+1, count); /* count-1 for cp+1, count+1 for NUL */
return 0;
#else
errno = ENOSYS;
return -1;
#endif
}
int get_sched_policy(int tid, SchedPolicy *policy)
{
initialize();
if (__sys_supports_schedgroups) {
char grpBuf[32];
if (getSchedulerGroup(tid, 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;
}
} else {
int rc = sched_getscheduler(tid);
if (rc < 0)
return -1;
else if (rc == SCHED_NORMAL)
*policy = SP_FOREGROUND;
else if (rc == SCHED_BATCH)
*policy = SP_BACKGROUND;
else {
errno = ERANGE;
return -1;
}
}
return 0;
}
int set_sched_policy(int tid, SchedPolicy policy)
{
initialize();
#if POLICY_DEBUG
char statfile[64];
char statline[1024];
char thread_name[255];
int fd;
sprintf(statfile, "/proc/%d/stat", tid);
memset(thread_name, 0, sizeof(thread_name));
fd = open(statfile, O_RDONLY);
if (fd >= 0) {
int rc = read(fd, statline, 1023);
close(fd);
statline[rc] = 0;
char *p = statline;
char *q;
for (p = statline; *p != '('; p++);
p++;
for (q = p; *q != ')'; q++);
strncpy(thread_name, p, (q-p));
}
if (policy == SP_BACKGROUND) {
LOGD("vvv tid %d (%s)", tid, thread_name);
} else if (policy == SP_FOREGROUND) {
LOGD("^^^ tid %d (%s)", tid, thread_name);
} else {
LOGD("??? tid %d (%s)", tid, thread_name);
}
#endif
if (__sys_supports_schedgroups) {
const char *grp = "";
if (policy == SP_BACKGROUND) {
grp = "bg_non_interactive";
}
if (add_tid_to_cgroup(tid, grp)) {
if (errno != ESRCH && errno != ENOENT)
return -errno;
}
} else {
struct sched_param param;
param.sched_priority = 0;
sched_setscheduler(tid,
(policy == SP_BACKGROUND) ?
SCHED_BATCH : SCHED_NORMAL,
¶m);
}
return 0;
}
#endif /* HAVE_SCHED_H */
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