Reputation: 337
I have an interesting (to me) problem... There are two threads, one for capturing data from std input and sending it through socket to server, and another one which receives data from blocking socket. So, when there's no reply from server, recv() call waits indefenitely, right? But instead of blocking only its calling thread, it blocks the overall process! Why this thing occurs?
boost::mutex nvtMutex;
boost::mutex strMutex;
boost::mutex quitMutex;
bool quit = false;
void *processServerOutput(void *arg)
{
NVT *nvt = (NVT*)arg;
while(1)
{
// Lock the quitMutex before trying to access to quit variable
quitMutex.lock();
if(quit)
{
quitMutex.unlock();
pthread_exit(NULL);
}
else
quitMutex.unlock();
// Receive output from server
nvtMutex.lock();
nvt->receive();
cout << Util::Instance()->iconv("koi8-r", "utf-8", nvt->getOutBuffer());
nvtMutex.unlock();
// Delay
sleep(1);
}
}
void *processUserInput(void *arg)
{
NVT *nvt = (NVT*)arg;
while(1)
{
// Get user's input
//cin.getline(str, 1023);
sleep(3);
strcpy(str, "hello");
// If we type 'quit', exit from thread
if(strcmp(str, "quit") == 0)
{
// Lock quit variable before trying to modify it
quitMutex.lock();
quit = true;
quitMutex.unlock();
// Exit from thread
pthread_exit(NULL);
}
// Send the input to server
nvtMutex.lock();
nvt->writeUserCommand(Util::Instance()->iconv("utf-8", "koi8-r", str));
nvt->send();
nvtMutex.unlock();
}
}
Upvotes: 3
Views: 2018
Reputation: 76601
You are holding the nvtMutex
inside the call to NVT::recv
. Since both threads need to lock the mutex to make it through an iteration, until NVT::recv
returns the other thread can't progress.
Without knowing the details of this NVT
class, it's impossible to know if you can safely unlock the mutex before calling NVT::recv
or if this class does not provide the proper thread safety you need.
Upvotes: 3
Reputation: 273706
If your code is implemented correctly, recv
blocks only the thread that invokes it.
If this isn't the case for you, show the minimal code sample that demonstrates the problem.
Upvotes: 1