How to avoid locking using lock_guard?
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https://en.cppreference.com/w/cpp/thread/lock_guard
(constructor)
constructs a lock_guard, optionally locking the given mutex
What would be the way to avoid locking if it is optional?
c++ multithreading locking mutex
asked Jan 4 at 6:16
Aquarius_GirlAquarius_Girl
7,29645151283
add a comment |
https://en.cppreference.com/w/cpp/thread/lock_guard
(constructor)
constructs a lock_guard, optionally locking the given mutex
What would be the way to avoid locking if it is optional?
c++ multithreading locking mutex
asked Jan 4 at 6:16
Aquarius_GirlAquarius_Girl
7,29645151283
3
Have you tried clicking on the(constructor)link to read more about it? It will tell you about the "optional" part and how to achieve it.
– Some programmer dude
Jan 4 at 6:26
@Someprogrammerdude No I hadn't. Thanks for pointing out.
– Aquarius_Girl
Jan 4 at 6:34
add a comment |
https://en.cppreference.com/w/cpp/thread/lock_guard
(constructor)
constructs a lock_guard, optionally locking the given mutex
What would be the way to avoid locking if it is optional?
c++ multithreading locking mutex
asked Jan 4 at 6:16
Aquarius_GirlAquarius_Girl
7,29645151283
https://en.cppreference.com/w/cpp/thread/lock_guard
(constructor)
constructs a lock_guard, optionally locking the given mutex
What would be the way to avoid locking if it is optional?
c++ multithreading locking mutex
c++ multithreading locking mutex
asked Jan 4 at 6:16
Aquarius_GirlAquarius_Girl
7,29645151283
asked Jan 4 at 6:16
Aquarius_GirlAquarius_Girl
7,29645151283
asked Jan 4 at 6:16
Aquarius_GirlAquarius_Girl
7,29645151283
asked Jan 4 at 6:16
Aquarius_GirlAquarius_Girl
7,29645151283
asked Jan 4 at 6:16
Aquarius_GirlAquarius_Girl
7,29645151283
7,29645151283
3
Have you tried clicking on the(constructor)link to read more about it? It will tell you about the "optional" part and how to achieve it.
– Some programmer dude
Jan 4 at 6:26
@Someprogrammerdude No I hadn't. Thanks for pointing out.
– Aquarius_Girl
Jan 4 at 6:34
add a comment |
3
Have you tried clicking on the(constructor)link to read more about it? It will tell you about the "optional" part and how to achieve it.
– Some programmer dude
Jan 4 at 6:26
@Someprogrammerdude No I hadn't. Thanks for pointing out.
– Aquarius_Girl
Jan 4 at 6:34
3
3
Have you tried clicking on the
(constructor) link to read more about it? It will tell you about the "optional" part and how to achieve it.– Some programmer dude
Jan 4 at 6:26
Have you tried clicking on the
(constructor) link to read more about it? It will tell you about the "optional" part and how to achieve it.– Some programmer dude
Jan 4 at 6:26
@Someprogrammerdude No I hadn't. Thanks for pointing out.
– Aquarius_Girl
Jan 4 at 6:34
@Someprogrammerdude No I hadn't. Thanks for pointing out.
– Aquarius_Girl
Jan 4 at 6:34
add a comment |
1 Answer
1
active
oldest
votes
This is one way to avoid having the lock_guard constructor lock the given mutex :
std::mutex mtx;
mtx.lock();
std::lock_guard<std::mutex> lck(mtx, std::adopt_lock);
The intention is to allow your lock_guard to take ownership of a mutex that you already locked.
From: https://en.cppreference.com/w/cpp/thread/lock_guard/lock_guard
explicit lock_guard( mutex_type& m ); (1) (since C++11)
lock_guard( mutex_type& m, std::adopt_lock_t t ); (2) (since C++11)
lock_guard( const lock_guard& ) = delete; (3) (since C++11)
Acquires ownership of the given mutex m.
1) Effectively calls m.lock(). The behavior is undefined if m is not a recursive mutex and the current thread already owns m.
2) Acquires ownership of the mutex m without attempting to lock it.
The behavior is undefined if the current thread does not own m.
3) Copy constructor is deleted.
The behavior is undefined if m is destroyed before the lock_guard object is.
edited Jan 4 at 6:56
Scheff
8,36821426
answered Jan 4 at 6:29
Sid SSid S
4,35021023
Doeslock_guard(mutex_type& m, std::adopt_lock_t t);check whethermis locked? In the case, it is not locked, doeslock_guard::~lock_guard()skip the call ofunlock()? I would expect this. However, I wonder it isn't mentioned in the cppreference doc. (An MCVE for demo would be nice.)
– Scheff
Jan 4 at 7:00
@Scheff, "The behavior is undefined if the current thread does not own m." - here, "does not own" means "have not locked". So you get undefined behavior if you pass an unlockedmutexto thelockguardconstructor.
– Sid S
Jan 4 at 7:22
May be, I focused too much on the "optional". I understood the question as "How to uselock_guardoptionally?" Reading it again I seem to have mis-understood this... (Sorry, my fault.)
– Scheff
Jan 4 at 7:47
add a comment |
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1 Answer
1
active
oldest
votes
1 Answer
1
active
oldest
votes
active
oldest
votes
active
oldest
votes
This is one way to avoid having the lock_guard constructor lock the given mutex :
std::mutex mtx;
mtx.lock();
std::lock_guard<std::mutex> lck(mtx, std::adopt_lock);
The intention is to allow your lock_guard to take ownership of a mutex that you already locked.
From: https://en.cppreference.com/w/cpp/thread/lock_guard/lock_guard
explicit lock_guard( mutex_type& m ); (1) (since C++11)
lock_guard( mutex_type& m, std::adopt_lock_t t ); (2) (since C++11)
lock_guard( const lock_guard& ) = delete; (3) (since C++11)
Acquires ownership of the given mutex m.
1) Effectively calls m.lock(). The behavior is undefined if m is not a recursive mutex and the current thread already owns m.
2) Acquires ownership of the mutex m without attempting to lock it.
The behavior is undefined if the current thread does not own m.
3) Copy constructor is deleted.
The behavior is undefined if m is destroyed before the lock_guard object is.
edited Jan 4 at 6:56
Scheff
8,36821426
answered Jan 4 at 6:29
Sid SSid S
4,35021023
Doeslock_guard(mutex_type& m, std::adopt_lock_t t);check whethermis locked? In the case, it is not locked, doeslock_guard::~lock_guard()skip the call ofunlock()? I would expect this. However, I wonder it isn't mentioned in the cppreference doc. (An MCVE for demo would be nice.)
– Scheff
Jan 4 at 7:00
@Scheff, "The behavior is undefined if the current thread does not own m." - here, "does not own" means "have not locked". So you get undefined behavior if you pass an unlockedmutexto thelockguardconstructor.
– Sid S
Jan 4 at 7:22
May be, I focused too much on the "optional". I understood the question as "How to uselock_guardoptionally?" Reading it again I seem to have mis-understood this... (Sorry, my fault.)
– Scheff
Jan 4 at 7:47
add a comment |
This is one way to avoid having the lock_guard constructor lock the given mutex :
std::mutex mtx;
mtx.lock();
std::lock_guard<std::mutex> lck(mtx, std::adopt_lock);
The intention is to allow your lock_guard to take ownership of a mutex that you already locked.
From: https://en.cppreference.com/w/cpp/thread/lock_guard/lock_guard
explicit lock_guard( mutex_type& m ); (1) (since C++11)
lock_guard( mutex_type& m, std::adopt_lock_t t ); (2) (since C++11)
lock_guard( const lock_guard& ) = delete; (3) (since C++11)
Acquires ownership of the given mutex m.
1) Effectively calls m.lock(). The behavior is undefined if m is not a recursive mutex and the current thread already owns m.
2) Acquires ownership of the mutex m without attempting to lock it.
The behavior is undefined if the current thread does not own m.
3) Copy constructor is deleted.
The behavior is undefined if m is destroyed before the lock_guard object is.
edited Jan 4 at 6:56
Scheff
8,36821426
answered Jan 4 at 6:29
Sid SSid S
4,35021023
Doeslock_guard(mutex_type& m, std::adopt_lock_t t);check whethermis locked? In the case, it is not locked, doeslock_guard::~lock_guard()skip the call ofunlock()? I would expect this. However, I wonder it isn't mentioned in the cppreference doc. (An MCVE for demo would be nice.)
– Scheff
Jan 4 at 7:00
@Scheff, "The behavior is undefined if the current thread does not own m." - here, "does not own" means "have not locked". So you get undefined behavior if you pass an unlockedmutexto thelockguardconstructor.
– Sid S
Jan 4 at 7:22
May be, I focused too much on the "optional". I understood the question as "How to uselock_guardoptionally?" Reading it again I seem to have mis-understood this... (Sorry, my fault.)
– Scheff
Jan 4 at 7:47
add a comment |
This is one way to avoid having the lock_guard constructor lock the given mutex :
std::mutex mtx;
mtx.lock();
std::lock_guard<std::mutex> lck(mtx, std::adopt_lock);
The intention is to allow your lock_guard to take ownership of a mutex that you already locked.
From: https://en.cppreference.com/w/cpp/thread/lock_guard/lock_guard
explicit lock_guard( mutex_type& m ); (1) (since C++11)
lock_guard( mutex_type& m, std::adopt_lock_t t ); (2) (since C++11)
lock_guard( const lock_guard& ) = delete; (3) (since C++11)
Acquires ownership of the given mutex m.
1) Effectively calls m.lock(). The behavior is undefined if m is not a recursive mutex and the current thread already owns m.
2) Acquires ownership of the mutex m without attempting to lock it.
The behavior is undefined if the current thread does not own m.
3) Copy constructor is deleted.
The behavior is undefined if m is destroyed before the lock_guard object is.
edited Jan 4 at 6:56
Scheff
8,36821426
answered Jan 4 at 6:29
Sid SSid S
4,35021023
This is one way to avoid having the lock_guard constructor lock the given mutex :
std::mutex mtx;
mtx.lock();
std::lock_guard<std::mutex> lck(mtx, std::adopt_lock);
The intention is to allow your lock_guard to take ownership of a mutex that you already locked.
From: https://en.cppreference.com/w/cpp/thread/lock_guard/lock_guard
explicit lock_guard( mutex_type& m ); (1) (since C++11)
lock_guard( mutex_type& m, std::adopt_lock_t t ); (2) (since C++11)
lock_guard( const lock_guard& ) = delete; (3) (since C++11)
Acquires ownership of the given mutex m.
1) Effectively calls m.lock(). The behavior is undefined if m is not a recursive mutex and the current thread already owns m.
2) Acquires ownership of the mutex m without attempting to lock it.
The behavior is undefined if the current thread does not own m.
3) Copy constructor is deleted.
The behavior is undefined if m is destroyed before the lock_guard object is.
edited Jan 4 at 6:56
Scheff
8,36821426
answered Jan 4 at 6:29
Sid SSid S
4,35021023
edited Jan 4 at 6:56
Scheff
8,36821426
edited Jan 4 at 6:56
Scheff
8,36821426
edited Jan 4 at 6:56
Scheff
8,36821426
8,36821426
answered Jan 4 at 6:29
Sid SSid S
4,35021023
answered Jan 4 at 6:29
Sid SSid S
4,35021023
answered Jan 4 at 6:29
Sid SSid S
4,35021023
4,35021023
Doeslock_guard(mutex_type& m, std::adopt_lock_t t);check whethermis locked? In the case, it is not locked, doeslock_guard::~lock_guard()skip the call ofunlock()? I would expect this. However, I wonder it isn't mentioned in the cppreference doc. (An MCVE for demo would be nice.)
– Scheff
Jan 4 at 7:00
@Scheff, "The behavior is undefined if the current thread does not own m." - here, "does not own" means "have not locked". So you get undefined behavior if you pass an unlockedmutexto thelockguardconstructor.
– Sid S
Jan 4 at 7:22
May be, I focused too much on the "optional". I understood the question as "How to uselock_guardoptionally?" Reading it again I seem to have mis-understood this... (Sorry, my fault.)
– Scheff
Jan 4 at 7:47
add a comment |
Doeslock_guard(mutex_type& m, std::adopt_lock_t t);check whethermis locked? In the case, it is not locked, doeslock_guard::~lock_guard()skip the call ofunlock()? I would expect this. However, I wonder it isn't mentioned in the cppreference doc. (An MCVE for demo would be nice.)
– Scheff
Jan 4 at 7:00
@Scheff, "The behavior is undefined if the current thread does not own m." - here, "does not own" means "have not locked". So you get undefined behavior if you pass an unlockedmutexto thelockguardconstructor.
– Sid S
Jan 4 at 7:22
May be, I focused too much on the "optional". I understood the question as "How to uselock_guardoptionally?" Reading it again I seem to have mis-understood this... (Sorry, my fault.)
– Scheff
Jan 4 at 7:47
Does
lock_guard(mutex_type& m, std::adopt_lock_t t); check whether m is locked? In the case, it is not locked, does lock_guard::~lock_guard() skip the call of unlock()? I would expect this. However, I wonder it isn't mentioned in the cppreference doc. (An MCVE for demo would be nice.)– Scheff
Jan 4 at 7:00
Does
lock_guard(mutex_type& m, std::adopt_lock_t t); check whether m is locked? In the case, it is not locked, does lock_guard::~lock_guard() skip the call of unlock()? I would expect this. However, I wonder it isn't mentioned in the cppreference doc. (An MCVE for demo would be nice.)– Scheff
Jan 4 at 7:00
@Scheff, "The behavior is undefined if the current thread does not own m." - here, "does not own" means "have not locked". So you get undefined behavior if you pass an unlocked
mutex to the lockguard constructor.– Sid S
Jan 4 at 7:22
@Scheff, "The behavior is undefined if the current thread does not own m." - here, "does not own" means "have not locked". So you get undefined behavior if you pass an unlocked
mutex to the lockguard constructor.– Sid S
Jan 4 at 7:22
May be, I focused too much on the "optional". I understood the question as "How to use
lock_guard optionally?" Reading it again I seem to have mis-understood this... (Sorry, my fault.)– Scheff
Jan 4 at 7:47
May be, I focused too much on the "optional". I understood the question as "How to use
lock_guard optionally?" Reading it again I seem to have mis-understood this... (Sorry, my fault.)– Scheff
Jan 4 at 7:47
add a comment |
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3
Have you tried clicking on the
(constructor)link to read more about it? It will tell you about the "optional" part and how to achieve it.– Some programmer dude
Jan 4 at 6:26
@Someprogrammerdude No I hadn't. Thanks for pointing out.
– Aquarius_Girl
Jan 4 at 6:34