std::adopt_lock
STD：：推迟[医]锁，STD：：尝试[医]到[医]锁，STD：：采用[医]锁
| Defined in header | | |
|---|---|---|
| constexpr std::defer_lock_t defer_lock {}; | | (since C++11) (until C++17) |
| inline constexpr std::defer_lock_t defer_lock {}; | | (since C++17) |
| constexpr std::try_to_lock_t try_to_lock {}; | | (since C++11) (until C++17) |
| inline constexpr std::try_to_lock_t try_to_lock {}; | | (since C++17) |
| constexpr std::adopt_lock_t adopt_lock {}; | | (since C++11) (until C++17) |
| inline constexpr std::adopt_lock_t adopt_lock {}; | | (since C++17) |
std::defer_lock，，，std::try_to_lock和std::adopt_lock是空struct标记类型的实例。std::defer_lock_t，，，std::try_to_lock_t和std::adopt_lock_t分别。
它们用于指定锁定策略。std::lock_guard，，，std::unique_lock和std::shared_lock...
| Type | Effect(s) |
|---|---|
| defer_lock_t | do not acquire ownership of the mutex |
| try_to_lock_t | try to acquire ownership of the mutex without blocking |
| adopt_lock_t | assume the calling thread already has ownership of the mutex |
例
二次
#include <mutex>
#include <thread>
struct bank_account {
explicit bank_account(int balance) : balance(balance) {}
int balance;
std::mutex m;
};
void transfer(bank_account &from, bank_account &to, int amount)
{
// lock both mutexes without deadlock
std::lock(from.m, to.m
// make sure both already-locked mutexes are unlocked at the end of scope
std::lock_guard<std::mutex> lock1(from.m, std::adopt_lock
std::lock_guard<std::mutex> lock2(to.m, std::adopt_lock
// equivalent approach:
// std::unique_lock<std::mutex> lock1(from.m, std::defer_lock
// std::unique_lock<std::mutex> lock2(to.m, std::defer_lock
// std::lock(lock1, lock2
from.balance -= amount;
to.balance += amount;
}
int main()
{
bank_account my_account(100
bank_account your_account(50
std::thread t1(transfer, std::ref(my_account), std::ref(your_account), 10
std::thread t2(transfer, std::ref(your_account), std::ref(my_account), 5
t1.join(
t2.join(
}
二次
另见
| defer_lock_ttry_to_lock_tadopt_lock_t (C++11)(C++11)(C++11) | tag type used to specify locking strategy (class) |
|---|---|
| (constructor) | constructs a lock_guard, optionally locking the given mutex (public member function of std::lock_guard) |
| (constructor) | constructs a unique_lock, optionally locking the supplied mutex (public member function of std::unique_lock) |
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