1. TSX has been broken in varying degrees in every architecture since haswell, and not always in a nice way like "always abort." In various steppings of haswell

1. TSX has been broken in varying degrees in every architecture since haswell, and not always in a nice way like "always abort." In various steppings of haswell and early broadwell TSX was in various states of disablement, meaning that sometimes the instructions were advertised (in cpuid etc) to work but had subtle bugs, sometimes were advertised to work but were disabled such that any RTM instruction caused SIGILL, and sometimes correctly advertised to not work. The detection of the state of TSX was sufficiently unreliable that glibc ended up with a blacklist of CPU model numbers that were too problematic to even try using TSX. 2. The pthread implementation of mutex using TSX behaved differently from the prior implementation in cases of misuse. This was deemed acceptable because applications that were impacted were using mutexes illegally, but the result was that a ton of software in all the distros started crashing randomly (IIRC the scenario was a double unlock. pre-TSX glibc didn't complain, post-TSX the program crashed or something). 3. TSX was not generally beneficial. The glibc implementation did something like try using a transaction 3 or 5 times before giving up. The worst-case performance of starting the transaction, going as far into the critical section as possible, aborting, repeat 2x, then finally taking the lock normally is much worse than just taking the lock.