UNIX for Dummies Questions & Answers

Hi all,

Is it possible to do the following in Linux (kernel 2.6.x):

- A user-space thread goes to "sleep". Using any call/mechanism
- On a hardware generated interrupt, the Interrupt handler (ISR) "wakes" the sleeping user-thread.

I have seen wait_event() and wake_up() but it appears that the two should be both user-mode or kernel-mode. Or can they be in different spaces?

I could use complete, semaphores or queues or anything else but it appears that any kind of such synchronization requires the shared object to be either in kernel-space or user-space.

Gaurav

Interfaces between kernel space and user space are generally accomplished through convenient pre-existing system calls and interfaces. Use something like a blocking read() or open() call to a device node or an interface under /proc. ACPI events are reported this way, when you push the power button things waiting to read from /proc/acpi/event are fed data like "[BUTTON]". This way should work for threads AND processes too, even arbitrarily from shell like how you can 'cat /proc/acpi/event' and see events pop up when the kernel reports them.