On Mon, Feb 24 2020 10:42:22 +0100, Martin Pieuchot wrote: > > Yes, that's what I'm trying to do. Yes, I've seen the current > > implementation -- that's why I started this thread, in an attempt to > > make them supported. :) > > > > See the followup patch -- sharing the semaphore between processes does > > work with it. > > Well ignoring the `pshared' argument is questionable.
It does feel strange, but a fully userspace implementation of semaphores (ie. using only mmap MAP_SHARED files for communication with other thread/processes) doesn't really have a meaningful distinction whether sharing happens between threads or processes. The other semaphore implementations I glanced at all had some kind of 'kernel semaphore'. I suppose a userspace implementation like this could store the pid of the process allowed to access the semaphore in struct __sem if pshared=0, and check that on every access, but I'm honestly not sure what value it brings for a userspace library to essentially prevent access to userspace memory if the application went through the effort to share that memory between processes anyway. -- Lauri Tirkkonen | lotheac @ IRCnet
