用多个线程处理SIGTERM的正确方法

我在Raspberry上有一个多线程程序，我想在其中处理SIGTERM并优雅地关闭一切。问题是我有一个后台线程在阻塞套接字上调用了recvfrom()。根据我从手册页中的理解，如果我退出我的处理程序，所有的系统调用都应该被唤醒，并返回-1和errno设置为EINTR。然而，在我的情况下，recvfrom呼叫一直处于挂起状态。

1) 总的来说，我理解得对吗？在这种情况下，所有有阻塞系统调用的线程都应该被信号唤醒？2) 可能是操作系统在我的电脑上设置了一些特殊的信号屏蔽吗？

有趣的是，我使用的是VideoCore原语，而不是pthread，也许这可能是原因？下面是一个小的测试示例：

#include <iostream>
#include <cstdlib>
#include <cstring>
#include <errno.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <unistd.h>
#include <signal.h>

#include "interface/vcos/vcos.h"
void SignalHandler(int nSignalNumber)
{
std::cout << "received signal " << nSignalNumber << std::endl;
}
void* ThreadMain(void* pArgument)
{
int nSocket = socket(AF_INET, SOCK_DGRAM, 0);
if (nSocket >= 0)
{
sockaddr_in LocalAddress;
memset(&LocalAddress, 0, sizeof(LocalAddress));
LocalAddress.sin_family = AF_INET;
LocalAddress.sin_addr.s_addr = INADDR_ANY;
LocalAddress.sin_port = htons(1234);
if (bind(nSocket, reinterpret_cast<sockaddr *>(&LocalAddress), sizeof(LocalAddress)) == 0)
{
sockaddr_in SenderAddress;
socklen_t nSenderAddressSize = sizeof(SenderAddress);
unsigned char pBuffer[512];
std::cout << "calling recvfrom()" << std::endl;
int nBytesReceived = recvfrom(nSocket, pBuffer, sizeof(pBuffer), 0, reinterpret_cast<struct sockaddr *>(&SenderAddress), &nSenderAddressSize);
if (nBytesReceived == -1)
{
if (errno == EINTR)
{
std::cout << "recvfrom() was interrupred by a signal" << std::endl;
}
else
{
std::cout << "recvfrom() failed with " << errno << std::endl;
}
}
}
else
{
std::cout << "bind() failed with " << errno << std::endl;
}
close(nSocket);
}
else
{
std::cout << "socket() failed with " << errno << std::endl;
}
return NULL;
}
int main(int argc, char** argv)
{
struct sigaction SignalAction;
memset(&SignalAction, 0, sizeof(SignalAction));
SignalAction.sa_handler = SignalHandler;
sigaction(SIGTERM, &SignalAction, NULL);
VCOS_THREAD_T Thread;
VCOS_STATUS_T nVcosStatus = vcos_thread_create(&Thread, "", NULL, ThreadMain, NULL);
if (nVcosStatus == VCOS_SUCCESS)
{
void* pData = NULL;
vcos_thread_join(&Thread, &pData);
}
else
{
std::cout << "vcos_thread_create() failed with " << nVcosStatus << std::endl;
}
return EXIT_SUCCESS;
}

它可以这样编译：

g++ test.cpp -I/opt/vc/include -L/opt/vc/lib -lvcos  -o test

当我运行它，然后在运行的实例上调用kill时，输出是：

calling recvfrom()
received signal 15

并且进程挂起。如果pthread的行为不同，我会尝试一下。

更新

好的，我更新了这个示例，生成了一个pthread线程，这个线程也没有退出。所以我假设信号没有填充到所有线程？

#include <iostream>
#include <cstdlib>
#include <cstring>
#include <errno.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <unistd.h>
#include <signal.h>
#include <pthread.h>
#include "interface/vcos/vcos.h"
void SignalHandler(int nSignalNumber)
{
std::cout << "received signal " << nSignalNumber << std::endl;
}
void* ThreadMain(void* pArgument)
{
const char* pThreadType = reinterpret_cast<const char*>(pArgument);
int nSocket = socket(AF_INET, SOCK_DGRAM, 0);
if (nSocket >= 0)
{
sockaddr_in LocalAddress;
memset(&LocalAddress, 0, sizeof(LocalAddress));
LocalAddress.sin_family = AF_INET;
LocalAddress.sin_addr.s_addr = INADDR_ANY;
LocalAddress.sin_port = htons(pThreadType[0] * 100);
if (bind(nSocket, reinterpret_cast<sockaddr *>(&LocalAddress), sizeof(LocalAddress)) == 0)
{
sockaddr_in SenderAddress;
socklen_t nSenderAddressSize = sizeof(SenderAddress);
unsigned char pBuffer[512];
std::cout << "calling recvfrom()" << std::endl;
int nBytesReceived = recvfrom(nSocket, pBuffer, sizeof(pBuffer), 0, reinterpret_cast<struct sockaddr *>(&SenderAddress), &nSenderAddressSize);
if (nBytesReceived == -1)
{
if (errno == EINTR)
{
std::cout << "recvfrom() was interrupred by a signal" << std::endl;
}
else
{
std::cout << "recvfrom() failed with " << errno << std::endl;
}
}
}
else
{
std::cout << "bind() failed with " << errno << std::endl;
}
close(nSocket);
}
else
{
std::cout << "socket() failed with " << errno << std::endl;
}
std::cout << pThreadType << " thread is exiting" << std::endl;
return NULL;
}
int main(int argc, char** argv)
{
struct sigaction SignalAction;
memset(&SignalAction, 0, sizeof(SignalAction));
SignalAction.sa_handler = SignalHandler;
sigaction(SIGTERM, &SignalAction, NULL);
VCOS_THREAD_T VcosThread;
VCOS_STATUS_T nVcosStatus = vcos_thread_create(&VcosThread, "", NULL, ThreadMain, const_cast<char*>("vcos"));
bool bJoinVcosThread = false;
if (nVcosStatus == VCOS_SUCCESS)
{
bJoinVcosThread = true;
}
else
{
std::cout << "vcos_thread_create() failed with " << nVcosStatus << std::endl;
}
pthread_t PthreadThread;
int nPthreadStatus = pthread_create(&PthreadThread, NULL, ThreadMain, const_cast<char*>("pthread"));
bool bJoinPthreadThread = false;
if (nPthreadStatus == 0)
{
bJoinPthreadThread = true;
}
else
{
std::cout << "pthread_create() failed with " << nPthreadStatus << std::endl;
}
if (bJoinVcosThread)
{
void* pData = NULL;
vcos_thread_join(&VcosThread, &pData);
}
if (bJoinPthreadThread)
{
void* pData = NULL;
pthread_join(PthreadThread, &pData);
}
return EXIT_SUCCESS;
}