Messages in this thread | | | Date | Tue, 30 Sep 2014 23:47:32 +0200 | From | Oleg Nesterov <> | Subject | Re: [PATCH 10/11] sched: Debug nested sleeps |
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On 09/30, Peter Zijlstra wrote: > > On Tue, Sep 30, 2014 at 12:13:44AM +0200, Oleg Nesterov wrote: > > On 09/24, Peter Zijlstra wrote: > > > > > > +#ifdef CONFIG_DEBUG_ATOMIC_SLEEP > > > + > > > +#define __set_task_state(tsk, state_value) \ > > > + do { \ > > > + (tsk)->task_state_change = _THIS_IP_; \ > > > + (tsk)->state = (state_value); \ > > > + } while (0) > > > > ... > > > > > @@ -7143,6 +7143,19 @@ void __might_sleep(const char *file, int > > > { > > > static unsigned long prev_jiffy; /* ratelimiting */ > > > > > > + /* > > > + * Blocking primitives will set (and therefore destroy) current->state, > > > + * since we will exit with TASK_RUNNING make sure we enter with it, > > > + * otherwise we will destroy state. > > > + */ > > > + if (WARN(current->state != TASK_RUNNING, > > > + "do not call blocking ops when !TASK_RUNNING; " > > > + "state=%lx set at [<%p>] %pS\n", > > > + current->state, > > > + (void *)current->task_state_change, > > > + (void *)current->task_state_change)) > > > + __set_current_state(TASK_RUNNING); > > > > Question: now that we have ->task_state_change, perhaps it makes sense > > to redefine fixup_sleep() > > > > #ifdef CONFIG_DEBUG_ATOMIC_SLEEP > > #define fixup_sleep() (current->task_state_change = 0) > > #else > > #define fixup_sleep() do { } while (0) > > #endif > > > > and make the WARN() above depend on task_state_change != 0 ? > > > > This is minor, but this way CONFIG_DEBUG_ATOMIC_SLEEP will not imply > > a subtle behavioural change. > > You mean the __set_current_state() that's extra?
Yes, and note that it only does __set_current_state(RUNNING) if CONFIG_DEBUG_ATOMIC_SLEEP. This means that disabling/enabling this option can, silently hide/uncover a bug.
> I would actually argue > to keep that since it makes the 'problem' much worse.
OK, I won't insist, but could you explain why the suggested change can make the problem (and which problem ;) worse?
Oleg.
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