std::try_lock (3) - Linux Manuals
std::try_lock: std::try_lock
Command to display std::try_lock manual in Linux: $ man 3 std::try_lock
NAME
std::try_lock - std::try_lock
Synopsis
Defined in header <mutex>
template< class Lockable1, class Lockable2, class... LockableN> (since C++11)
int try_lock( Lockable1& lock1, Lockable2& lock2, LockableN&... lockn);
Tries to lock each of the given Lockable objects lock1, lock2, ..., lockn by calling try_lock in order beginning with the first.
If a call to try_lock fails, no further call to try_lock is performed, unlock is called for any locked objects and a 0-based index of the object that failed to lock is returned.
If a call to try_lock results in an exception, unlock is called for any locked objects before rethrowing.
Parameters
lock1, lock2, ... , lockn - the Lockable objects to lock
Return value
-1 on success, or 0-based index value of the object that failed to lock.
Example
The following example uses std::try_lock to periodically tally and reset counters running in separate threads.
// Run this code
#include <mutex>
#include <vector>
#include <thread>
#include <iostream>
#include <functional>
#include <chrono>
int main()
{
int foo_count = 0;
std::mutex foo_count_mutex;
int bar_count = 0;
std::mutex bar_count_mutex;
int overall_count = 0;
bool done = false;
std::mutex done_mutex;
auto increment = [](int &counter, std::mutex &m, const char *desc) {
for (int i = 0; i < 10; ++i) {
std::unique_lock<std::mutex> lock(m);
++counter;
std::cout << desc << ": " << counter << '\n';
lock.unlock();
std::this_thread::sleep_for(std::chrono::seconds(1));
}
};
std::thread increment_foo(increment, std::ref(foo_count),
std::ref(foo_count_mutex), "foo");
std::thread increment_bar(increment, std::ref(bar_count),
std::ref(bar_count_mutex), "bar");
std::thread update_overall([&]() {
done_mutex.lock();
while (!done) {
done_mutex.unlock();
int result = std::try_lock(foo_count_mutex, bar_count_mutex);
if (result == -1) {
overall_count += foo_count + bar_count;