utrace_control(,,UTRACE_SINGLESTEP)

[Oleg Nesterov]

On 10/29, Oleg Nesterov wrote:
>
> In this case I confused again. Let's forget about get_user_pages() under
> spin_lock(), pretend it works.
>
> Two engines, E1 and E2, the tracee sleeps in utrace_resume()->utrace_stop().
>
> E1 does utrace_control(UTRACE_RESUME), E2 does utrace_control(UTRACE_SINGLESTEP).
> How this can work?
>
> If E2 calls utrace_control() first, the subsequent UTRACE_RESUME does
> user_disable_single_step(), and (in general) E2 has no chance to re-assert
> SINGLESTEP.

Looks like, 26fefca "sticky resume action" fixes this...

Oleg.