Home/ Questions/Q 6757267
In Process

The Archive Base Latest Questions

Editorial Team
  • 0
Asked: 2026-05-26T13:37:39+00:00

I’m looking for a wait/signal synchronization primitive in IO/Kit working like : Thread1 :

  • 0

I’m looking for a wait/signal synchronization primitive in IO/Kit working like :

Thread1 : wait(myEvent) // Blocking thread1

Thread2 : wait(myEvent) // Blocking thread2

Thread3 : signal(myEvent) // Release one of thread1 or thread2

This can’t be done using an IOLock since the lock/unlock operations would be made from different threads, which is a bad idea according to some doc I’ve read.

Thread1, 2, 3 can be user threads or kernel threads.

I’d also like to have an optional time out with the wait operation.

Thanks for your help !

Share

Leave an answer

You must login to add an answer.

Need An Account,

1 Answer

  1. Editorial Team

    You want the function IOLockSleepDeadline(), declared in <IOKit/IOLocks.h>.

    You set up a single IOLock somewhere with IOLockAlloc() before you begin. Then, threads 1 and 2 lock the IOLock with IOLockLock() and immediately relinquish the lock and go to sleep by calling IOLockSleepDeadline(). When thread 3 is ready, it calls IOLockWakeup() (with oneThread = true if you only want to wake a single thread). This causes thread 1 or 2 to wake up and immediately acquire the lock (so they need to Unlock or sleep again).

    IOLockSleep() works similarly, but without the timeout.

    You can do something similar using the IOCommandGate’s commandSleep() method which may be more appropriate if your driver already is centred around an IOWorkLoop.

    • 0