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

During an open water swim, it's easy to lose your direction. With all the splash, it can be quite hard to see the next buoy, so I look behind it for something bigger, like a tree or a building, and aim for that instead.

Jonathan Brownlee

The only time I ever met a character that I wrote was when I met Ian McKellan, when he was playing Magneto in the 'X-Men' movies.

Grant Morrison

You are the best thing thats ever been mine.

Taylor Swift

Honesty is never seen sitting astride the fence.

Lemuel K. Washburn

The harder you work... and visualize something, the luckier you get.

Seal

I tend to think that the best face of humanity is that we learn. We explore, we study, we think.

Kurt Busiek

Dialogue is the fundamental unfolding of a gift of oneself to another.

Pope Benedict XVI

Creative things have to sell to get acknowledged as such.

Steve Wozniak

I can recall back in 1998, in August of that year, when we had a horrible disaster along the Mexican border in the town of Del Rio. At the time, FEMA was the shining star of the federal government. It's now perceived as many to be the dullest knife in the drawer. Right or wrong, that's the perception.

Henry Bonilla

Any artwork is part of something larger, grander and, you know, the situation that it's in is very important.

Robert Barry

Geraldo has been in Lebanon. He has done some excellent reporting out of there, and of course, we now know by virtue of the president's speech on Tuesday night that the terrorist organizations that operate in that area are now on the list.

Brit Hume

To believe in yourself and to follow your dreams, to have goals in life and a drive to succeed, and to surround yourself with the things and the people that make you happy - this is success!

Sasha Azevedo

Decency is indecencys conspiracy of silence.

George Bernard Shaw

Let sleeping dogs lie

Unknown

I came out of a culture when there wasn't tweeting and everyone with a camera in their hands. I didn't grow up with it, so I'm not always thinking about it, but there have been times when I looked over, and I saw that someone was recording my conversation.

Rene Russo

I didn't want to stop before my time was up.

Misty May-Treanor

Ultimately, the court is heading to a doctrine of 'separation of campaign and state.' This doctrine, like separation of church and state or separation of military and civilian authority, is not explicit in the Constitution but flows naturally from its structure and commitment to freedom and democracy.

Bradley A. Smith

When all is said and done, more is said than done.

Lou Holtz

If I just do everything the opposite of what my dad did, I think that will make things pretty easy. I can joke about it now because I'm past that stage where it used to hurt. By having a kid, it's gone. I could take all that negative energy that I had and put it in a positive way.

Derrick Rose

With the responsibility of being a professional athlete, I believe that it is on us to go out there and help people.

Torrey Smith

We hope we can slow or possibly reverse the symptoms of Alzheimer's.

Gregory Benford

The biggest thing politically within fashion is that the clothing should be displayed on different body shapes.

Zac Posen

Folks, I've been straight for seventeen days... Not all in a row.

Sam Kinison

The Constitution was about a limitation on power.

Roy Moore