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      1 /*
      2  * Copyright (C) 2009-2016 The Android Open Source Project
      3  *
      4  * Licensed under the Apache License, Version 2.0 (the "License");
      5  * you may not use this file except in compliance with the License.
      6  * You may obtain a copy of the License at
      7  *
      8  *      http://www.apache.org/licenses/LICENSE-2.0
      9  *
     10  * Unless required by applicable law or agreed to in writing, software
     11  * distributed under the License is distributed on an "AS IS" BASIS,
     12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     13  * See the License for the specific language governing permissions and
     14  * limitations under the License.
     15  */
     16 
     17 #define LOG_TAG "Service"
     18 
     19 #include <errno.h>
     20 #include <stdio.h>
     21 #include <string.h>
     22 #include <sys/system_properties.h>
     23 #include <unistd.h>
     24 
     25 #include <android-base/properties.h>
     26 #include <android-base/stringprintf.h>
     27 #include <log/log.h>
     28 #include <sysutils/ServiceManager.h>
     29 
     30 ServiceManager::ServiceManager() {
     31 }
     32 
     33 // The length of a service name should not exceed SERVICE_NAME_MAX. Starting
     34 // a service is done by writing its name to the "ctl.start" system property
     35 // and stopping a service is done by writing its name to "ctl.stop". If a
     36 // service name is too long to fit in a property, you won't be able to start
     37 // or stop it.
     38 static constexpr size_t SERVICE_NAME_MAX = PROP_VALUE_MAX;
     39 
     40 /* The maximum amount of time to wait for a service to start or stop,
     41  * in micro-seconds (really an approximation) */
     42 #define  SLEEP_MAX_USEC     2000000  /* 2 seconds */
     43 
     44 /* The minimal sleeping interval between checking for the service's state
     45  * when looping for SLEEP_MAX_USEC */
     46 #define  SLEEP_MIN_USEC      200000  /* 200 msec */
     47 
     48 int ServiceManager::start(const char *name) {
     49     if (strlen(name) > SERVICE_NAME_MAX) {
     50         SLOGE("Service name '%s' is too long", name);
     51         return 0;
     52     }
     53 
     54     if (isRunning(name)) {
     55         SLOGW("Service '%s' is already running", name);
     56         return 0;
     57     }
     58 
     59     SLOGD("Starting service '%s'", name);
     60     android::base::SetProperty("ctl.start", name);
     61 
     62     int count = SLEEP_MAX_USEC;
     63     while(count > 0) {
     64         usleep(SLEEP_MIN_USEC);
     65         count -= SLEEP_MIN_USEC;
     66         if (isRunning(name))
     67             break;
     68     }
     69     if (count <= 0) {
     70         SLOGW("Timed out waiting for service '%s' to start", name);
     71         errno = ETIMEDOUT;
     72         return -1;
     73     }
     74     SLOGD("Sucessfully started '%s'", name);
     75     return 0;
     76 }
     77 
     78 int ServiceManager::stop(const char *name) {
     79     if (strlen(name) > SERVICE_NAME_MAX) {
     80         SLOGE("Service name '%s' is too long", name);
     81         return 0;
     82     }
     83 
     84     if (!isRunning(name)) {
     85         SLOGW("Service '%s' is already stopped", name);
     86         return 0;
     87     }
     88 
     89     SLOGD("Stopping service '%s'", name);
     90     android::base::SetProperty("ctl.stop", name);
     91 
     92     int count = SLEEP_MAX_USEC;
     93     while(count > 0) {
     94         usleep(SLEEP_MIN_USEC);
     95         count -= SLEEP_MIN_USEC;
     96         if (!isRunning(name))
     97             break;
     98     }
     99 
    100     if (count <= 0) {
    101         SLOGW("Timed out waiting for service '%s' to stop", name);
    102         errno = ETIMEDOUT;
    103         return -1;
    104     }
    105     SLOGD("Successfully stopped '%s'", name);
    106     return 0;
    107 }
    108 
    109 bool ServiceManager::isRunning(const char *name) {
    110     std::string property_name = android::base::StringPrintf("init.svc.%s", name);
    111     return (android::base::GetProperty(property_name, "") == "running");
    112 }
    113