Killing a pthread waiting on a condition variable

Question

I have a pthread waiting on a condition variable using pthread_cond_wait(). It\'s waiting for data from a queue structure that is filled by another thread. I want

Answer 1

pthread_cancel should wake a thread that is blocked in pthread_cond_wait --- this is one of the required cancellation points. If it doesn't work then something is wrong.

The first thing to check is that cancellation is indeed enabled on the target thread --- explicitly call pthread_setcancelstate(PTHREAD_CANCEL_ENABLE,&oldstate) on the target thread to make sure. If that doesn't work, then cancellation is broken on your platform and you'll have to resort to alternatives such as setting a "please stop now" flag and signalling the condition variable.

Do not use asynchronous cancellation unless you really know what you are doing --- it can trigger the cancellation in the middle of any operation (e.g. in the middle of setting up a function call stack frame or running a destructor), and thus can leave your code in a thoroughly inconsistent state. Writing async-cancel-safe code is hard.

Incidentally pthread_kill does not kill a thread --- it sends a signal to it.