Oleg Nesterov <[email protected]> writes: > On 02/21, [email protected] wrote: >> >> In PT_SEIZED + LISTEN mode SIGSTOP/SIGCONT signals cause a wakeup >> against __TASK_TRACED. If this races with the ptrace_unfreeze_traced at >> the end of a PTRACE_LISTEN, this can wake the task /after/ the check >> against __TASK_TRACED, but before the reset of state to TASK_TRACED. > > Oh, thanks... > > note also that PTRACE_LISTEN itself can do ptrace_signal_wake_up(true), > >> This causes it to instead clobber TASK_WAKING, > > even if it is already TASK_RUNNING it is simply wrong to set TASK_TRACED > in both cases, right?
Yeah, that's also wrong and could possibly lead to different errors, but is likely to work out by accident when say ttwu checks on_rq and sees true. > > Thanks. The patch looks good at first glance, but let me think a bit... > perhaps we should change PTRACE_LISTEN instead, not sure. > > Oleg.
