Re: [PATCH 1/1] stop_machine: touch_nmi_watchdog() after MULTI_STOP_PREPARE

2016-07-27 Thread Thomas Gleixner
On Tue, 26 Jul 2016, Oleg Nesterov wrote: > Suppose that stop_machine(fn) hangs because fn() hangs. In this case NMI > hard-lockup can be triggered on another CPU which does nothing wrong and > the trace from nmi_panic() won't help to investigate the problem. > > And this change "fixes" the proble

[PATCH 1/1] stop_machine: touch_nmi_watchdog() after MULTI_STOP_PREPARE

2016-07-26 Thread Oleg Nesterov
Suppose that stop_machine(fn) hangs because fn() hangs. In this case NMI hard-lockup can be triggered on another CPU which does nothing wrong and the trace from nmi_panic() won't help to investigate the problem. And this change "fixes" the problem we (seem to) hit in practice. - stop_two_cpus(0,