Re: [Adeos-main] wake_up_interruptible ?

[Gilles Chanteperdrix <gilles.chanteperdrix@xenomai.org>]

Alexis Berlemont wrote:
 > Hi,
 > 
 > 
 > > I've got a kernel module which creates a chrdev.
 > > In the read file operation I have a interruptible_sleep_on.
 > > Now I want to wake it up from an IPIPE interrupt handler
 > > (i.e. unblock the read operation from user-space on the
 > > chrdev), but I bet wake_up_interruptible is forbidden
 > > in HRT context, isn't it ?
 > 
 > Why not using a semaphore : 
 > 
 > in your read fops function :
 > 
 > down_interruptible(pointer_read_sem);
 > 
 > in your IPIPE interrupt handler:
 > 
 > up(pointer_read_sem);
 > 
 > In an interrupt handler, I think you can use a Linux semaphore. I am quite 
 > sure semaphores are used in the Xenomai pipe implementation.

For the "up" function to work properly, Linux scheduler data have to be
in a consistent state. But with the IPIPE patch, Linux may be preempted
by a higher priority domain at any point where hardware interrupts are
not disabled, and where scheduler data are not necessarily in a
consistent state.

One way to wake up a regular Linux thread from a higher priority domain
interrupt handler is to propagate this interrupt after HRT processing in
higher priority domains and run wake_up_interruptible from Linux domain
interrupt handler.

-- 


					    Gilles Chanteperdrix.