Hi... > Ive a user app and a device driver sharing memory via mmap. This > block of memory contains info for a memory allocator. This is used by > the user app to get memory or to decide to do another mmap. Now the > kernel can basically return memory to the freelist, but doesnt want > to be competing with the user app and corrupt the freelist. I obv > dont want to make the kernel wait for the userapp(although i can > guarantee that no deadlocks will ever occur). I would like to signal > the process , the address within its process space that can be added > to the freelist. Im a bit lost on the way to do this..Any pointers? OK, from what I read above, sounds like you want to implement non blocking notification to user space so user space knows which block is freed, am I correct? The way I see it, there are two "actors" competing here: user and kernel space (kernel thread(s)?). So, as long as they are sharing the same free-list, I think you're enforced to implement locking mechanism, hence the need of signaling. How about this: let the kernel space manage the freelist completely? After all, (from what I read) it is the kernel space that actually uses the memory block, right? That way, only one side that actually touches the freelist. And about the synchronization, perhaps you can use signal (e.g using force_signal()) or do a read on /proc entry that in turns sleeps in a notifier. Doable? Sorry...can't give any code snippets... regards, Mulyadi -- Kernelnewbies: Help each other learn about the Linux kernel. Archive: http://mail.nl.linux.org/kernelnewbies/ FAQ: http://kernelnewbies.org/faq/
