On 08/07/16 11:40, Paolo Bonzini wrote: > Even better: add a "bool *tb_locked" argument to tb_find_slow, and > don't move the mmap_lock release. Then tb_find_fast knows directly > whether tb_lock is taken, and you don't need any of tb_lock_reset > or mmap_lock_reset.
I think we can do even better. One option is using a separate tiny lock to protect direct jump set/reset instead of tb_lock. Another option which I've had in my mind for some time is to make direct jump set/reset thread-safe. We already have thread-safe TB patching. The only question is the right order of operations and handling jmp_list_next/jmp_list_first safely. I think that could be done by removing tb_remove_from_jmp_list() and making RCU-like manipulation with jmp_list_next/jmp_list_first. What do you think? Kind regards, Sergey
