android上的pthread_create警告

Question

调用pthread_create函数后,我收到下一条消息:

W/libc(26409):pthread_create sched_setscheduler调用失败:不允许操作

用于创建线程的代码是:

pthread_attr_t threadAttr;
int ret = pthread_attr_init(&threadAttr);
//code to check ret - it's 0

size_t guard_size = 0;
pthread_attr_getguardsize(&threadAttr, &guard_size);
ret = pthread_attr_setstacksize(&threadAttr, myStackSize + guard_size);
//code to check ret - it's 0

ret = pthread_attr_setdetachstate(&threadAttr, PTHREAD_CREATE_DETACHED);
//code to check ret - it's 0

ret = pthread_attr_setschedpolicy(&threadAttr, SCHED_FIFO);
//code to check ret - it's 0

sched_param  schedParam;
schedParam.sched_priority = myPriority; //it's 16
ret = pthread_attr_setschedparam(&threadAttr, &schedParam);
//code to check ret - it's 0

// Create the thread
ret = pthread_create(&myHandle, &threadAttr, RunCallback, (void *)myData);
//code to check ret - it's 0
//code to check myHandle - it's > 0

// Delete attribute
pthread_attr_destroy(&threadAttr);

请注意,在命中RunCallback中的断点之前,该消息将显示在logcat中.

你知道为什么我有这个警告吗？忽视它是否安全 - 如果是,为什么？

PS:代码在具有4.4.2 OS版本(内部版本号KOT49H)的Nexus 4设备上作为本机活动运行.

Answer 1

使用调度策略属性创建线程时,您要求设置特定的调度策略(http://man7.org/linux/man-pages/man3/pthread_attr_getschedpolicy.3.html).根据http://man7.org/linux/man-pages/man2/sched_setscheduler.2.html,您正在设置的策略SCHED_FIFO是一个实时策略.根据http://man7.org/linux/man-pages/man7/capabilities.7.html,将调度策略设置为实时策略需要CAP_SYS_NICE功能.因此,除非您具有该功能,否则pthread_create调用将失败.

要解决此问题,请删除scheduler属性(并使用默认调度),或者确保使用正确的功能启动进程(例如,以root身份启动并删除除CAP_SYS_NICE之外的所有权限).