* Rich Felker: > On Thu, Nov 22, 2018 at 04:11:45PM +0100, Florian Weimer wrote: >> * Mathieu Desnoyers: >> >> > Thoughts ? >> > >> > /* Unregister rseq TLS from kernel. */ >> > if (has_rseq && __rseq_unregister_current_thread ()) >> > abort(); >> > >> > advise_stack_range (pd->stackblock, pd->stackblock_size, (uintptr_t) pd, >> > pd->guardsize); >> > >> > /* If the thread is detached free the TCB. */ >> > if (IS_DETACHED (pd)) >> > /* Free the TCB. */ >> > __free_tcb (pd); >> >> Considering that we proceed to free the TCB, I really hope that all >> signals are blocked at this point. (I have not checked this, though.) >> >> Wouldn't this address your concern about access to the rseq area? > > I'm not familiar with glibc's logic here, but for other reasons, I > don't think freeing it is safe until the kernel task exit futex (set > via clone or set_tid_address) has fired. I would guess __free_tcb just > sets up for it to be reclaimable when this happens rather than > immediately freeing it for reuse. Right, but in case of user-supplied stacks, we actually free TLS memory at this point, so signals need to be blocked because the TCB is (partially) gone after that. Thanks, Florian
