pthread_cond_wait() simultaneously unlock the mutex (so that other threads can modify the linked list) and wait on the condition (so that pthread_cond_wait() will wake up when it is "signalled" by another thread). Now that the mutex is unlocked, other threads can access and modify the linked list, possibly adding items

Tony Nemo

Threads in C

pthreads library and threaded programming in C

#programming

#threads

#CS

Tony Nemo

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"dead list" that contains all stopped threads and then have a special cleanup thread that simply waits for an item to be added to the list. The cleanup thread calls pthread_join() to merge it with itself. Now your entire cleanup will be handled neatly and efficiently in a single thread.

Tony Nemo

mutexes are used to serialize access to *shared data*. Don't use them for non-shared data, and don't use them if your program's logic ensures that only one thread is accessing a particular data structure at a single time.

Tony Nemo

if you are using shared data, use mutexes for both reading and writing. Surround your read and write sections with pthread_mutex_lock() and pthread_mutex_unlock(), or use them any time a program's invariant is temporarily broken.

Tony Nemo

pthread_mutex_destroy() does not free the memory used to store the pthread_mutex_t. It's up to you to free() your own memory. Also remember that both pthread_mutex_init() and pthread_mutex_destroy() return zero on success.

Tony Nemo

pthread_mutex_lock() accepts a single pointer to a mutex to lock. If the mutex already happens to be locked, the caller will go to sleep. When the function returns, the caller will be woken up (obviously), and the caller will also now hold the lock. This call either returns zero on success.

Tony Nemo

You should always unlock a mutex that you've locked as soon as safely possible (to increase performance). And you should never unlock a mutex that you don't hold a lock for

Tony Nemo

When you call pthread_mutex_trylock() you'll attempt to lock the mutex. If the mutex is currently unlocked you'll get the lock, and this function will return zero. However, if the mutex is locked this call won't block. Rather, it will return a non-zero EBUSY error value.

Tony Nemo

pthread_cond_wait() call has not yet returned. Unlocking the mutex happens immediately, but waiting on the condition mycond is normally a blocking operation, meaning that our thread will go to sleep, consuming no CPU cycles until it is woken up.

Tony Nemo

This is exactly what we want to happen. Our thread is sleeping, waiting for a particular condition to become true, without performing any kind of busy polling that would waste CPU time. From our thread's perspective, it's simply waiting for the pthread_cond_wait() call to return.

Tony Nemo

Immediately after unlocking the mutex, thread 2 calls the function pthread_cond_broadcast(&mycond). By doing so, thread 2 will cause all threads waiting on the mycond condition variable to immediately wake up. This means that our first thread (which is in the middle of a pthread_cond_wait() call) will now wake up.

Tony Nemo

After thread 2 called pthread_cond_broadcast(&mymutex) you might think that thread 1's pthread_cond_wait() will immediately return. Not so! Instead, pthread_cond_wait() will perform one last operation: relock mymutex. Once pthread_cond_wait() has the lock, it will then return and allow thread 1 to continue execution.

Tony Nemo

Those who forget good and evil and seek only to know the facts are more likely to achieve good than those who view the world through the distorting medium of their own desires.

Bertrand Russell

'Grandmother' doesn't mean that you have gray hair and you retire and stay home cooking cakes for your grandchildren.

Carine Roitfeld

You go through a process of refinement and getting rid of the excesses of your early youth in terms of your excitement about what theatre can do.

Stephen Daldry

One of the problems with posing a 'bold new plan' is that you can't just extrapolate from previous plans.

Nathan Myhrvold

The time is always right to do what is right.

Martin Luther King, Jr.

Its a round ball and a round bat and you got to hit it square.

Pete Rose

I don't necessarily think that installation is the only way to go. It's just a label for certain kinds of arrangements.

Barbara Kruger

God has a timeline. And because of Bethlehem, we have an idea where we stand on it.

Max Lucado

Yes, I get a report from BMI about the frequency of performances, and it is very surprising. They played one of my most advanced pieces, and one of my most unusual ones on the radio.

Elliott Carter

I'm really into, like, electric pop music and dubstep, things like that.

Chandler Riggs

If you're poor and you do something stupid, you're nuts. If you're rich and do something stupid, you're eccentric.

Bobby Heenan

Although a crisp texture is the single most prized quality in an apple - even more desirable than taste, according to one study - crispness is more a matter of acoustics than of mouth feel.

John Seabrook

O ye gods, grant unto me to have little and to want nothing.

Apollonius of Tyana

I'm a bit nerdy about accents. I love it.

Rebecca Hall

College is a magic time. Yes, you're young and fickle, but you want to be part of this college experience... Then you graduate from that. You have your first job, moving to a new city.

David Sze

In Islam, the legislative power and competence to establish laws belong exclusively to God Almighty.

Ruhollah Khomeini

On foreign policy, Obama has talked softly and carried a big stick.

George Packer

You women could make someone fall in love even with a lie.

Georg Buchner

In prison, those things withheld from and denied to the prisoner become precisely what he wants most of all.

Eldridge Cleaver

The snake kills by squeezing very slowly. This is how the civilized world slowly, slowly pushes into the forest and takes away the world that used to be.

James Cameron

Too many mothers have lost their children, for thousands of different reasons.

Debbie Reynolds

Don't let the secret recipe die with the inventor.

Nathan Myhrvold

If a female is good-looking, it totally decreases her credibility. Now she's not a good athlete - she's only good in these track meets because she's good-looking.

Lolo Jones

Trying to get over guys and knock them out, that's what fires me up. Decision victories, whoop dee doo, but finishing guys fires me up.

Robbie Lawler