Pthreads: How to get pthread_cond_signal to immediately wakeup waiters

[shaunp]

Hello all,

First, I'm new to Linux and pthread programming and recently discovered that calling pthread_cond_signal does not immediately wakeup higher priority waiting threads. Instead, the low priority thread which calls pthread_cond_signal is allowed to execute for a bit before the high priority waiting thread executes. However, I'd like to eliminate the scheduling delay. My goal is to find a solution which allows threads to signal a condition variable and immediately wakeup higher priority waiters.

My current approach to call sched_yield after every call to pthread_cond_signal. However, I would like to find an alternative which preferably does not require modifications to my code. Are there other solutions available and, if so, how can I use them? Are there kernel/pthread settings available or alternate schedulers available to give this behavior? Does the RT-Preempt patch give this behavior?

Best Regards,
Shaun

[Rubberman]

Is your real need for deterministic real-time performance? If so, then Linux is not the solution. Check out QNX for that sort of requirement.

[shaunp]

I am porting software from a commercial RTOS to Linux and cannot choose a different OS. Please understand that I appreciate your advice, but I need another approach. Given that I'm finding Linux options such as CONFIG_PREEMPT, the RT-Preempt patch was created, etc. I am hopeful another solution exists other than avoiding Linux entirely and am checking into potential options.

BTW - Here is one site discussing how Linux is suitable for real-time:
(Linux forums is blocking the link since I have fewer than 15 posts. Search for "Anatomy of real-time Linux architectures" on Google" instead)

Ultimately, I am not sure what pthread behavior I can acheive with the combinations of options. Do you know what the pthread behavior is with CONFIG_PREEMPT or with the RT-Preempt patch?