On Thu, May 02, 2024 at 11:51:56AM +0200, Florian Weimer wrote: > * Christian Brauner: > > > Unless I'm missing something the question here is PID (as in TGID aka > > thread-group leader id gotten via getpid()) vs TID (thread specific id > > gotten via gettid()). You want the thread-specific id as you want to > > interact with the futex state of a specific thread not the thread-group > > leader. > > > > Aside from that TIDs are subject to the same race conditions that PIDs > > are. They are allocated from the same pool (see alloc_pid()). > > For most mutex types (but not robust mutexes), it is undefined in > userspace if a thread exits while it has locked a mutex. Such a usage > condition would ensure that the race doesn't happen, I believe. The argument is a bit shaky imho because the race not being able to happen is predicated on no one being careless enough to exit with a mutex held. That doesn't do anything against someone doing it on purpose. > > From a glibc perspective, we typically cannot use long-term file > descriptors (that are kept open across function calls) because some > applications do not expect them, or even close them behind our back. Yeah, good point. Note, I suggested it as an extension not as a replacement for the TID. I still think it would be a useful extension in general.
