Virtualization - Sep 2022 - [PATCH v3 6/6] freezer,sched: Rewrite core freezer logic

Am 26.09.22 um 15:37 schrieb Peter Zijlstra:
> On Mon, Sep 26, 2022 at 03:23:10PM +0200, Christian Borntraeger wrote:
>> Am 26.09.22 um 14:55 schrieb Peter Zijlstra:
>>
>>> Could you please test with something like the below on? I can boot
that
>>> with KVM, but obviously I didn't suffer any weirdness to begin
with :/
>>>
>>> ---
>>> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
>>> index 4e6a6417211f..ef9ccfc3a8c0 100644
>>> --- a/kernel/sched/core.c
>>> +++ b/kernel/sched/core.c
>>> @@ -4051,6 +4051,8 @@ try_to_wake_up(struct task_struct *p,
unsigned int state, int wake_flags)
>>>    	unsigned long flags;
>>>    	int cpu, success = 0;
>>> +	WARN_ON_ONCE(state & TASK_FREEZABLE);
>>> +
>>>    	preempt_disable();
>>>    	if (p == current) {
>>>    		/*
>>
>> Does not seem to trigger.
> 
> Moo -- quite the puzzle this :/ I'll go stare at it more then.
Hmm,

#define ___wait_is_interruptible(state)                                        
\
         (!__builtin_constant_p(state) ||                                       
\
                 state == TASK_INTERRUPTIBLE || state == TASK_KILLABLE)         
\

That would not trigger when state is also TASK_FREEZABLE, no?

On Mon, Sep 26, 2022 at 05:49:16PM +0200, Christian Borntraeger wrote:
> Hmm,
> 
> #define ___wait_is_interruptible(state)                                    
\
>         (!__builtin_constant_p(state) ||                                   
\
>                 state == TASK_INTERRUPTIBLE || state == TASK_KILLABLE)     
\
> 
> That would not trigger when state is also TASK_FREEZABLE, no?
Spot on!

signal_pending_state() writes that as:

	state & (TASK_INTERRUPTIBLE | TASK_WAKEKILL)

which is the correct form.

diff --git a/include/linux/wait.h b/include/linux/wait.h
index 14ad8a0e9fac..7f5a51aae0a7 100644
--- a/include/linux/wait.h
+++ b/include/linux/wait.h
@@ -281,7 +281,7 @@ static inline void wake_up_pollfree(struct wait_queue_head
*wq_head)
 
 #define ___wait_is_interruptible(state)						\
 	(!__builtin_constant_p(state) ||					\
-		state == TASK_INTERRUPTIBLE || state == TASK_KILLABLE)		\
+	 (state & (TASK_INTERRUPTIBLE | TASK_WAKEKILL)))
 
 extern void init_wait_entry(struct wait_queue_entry *wq_entry, int flags);
 

Let me go git-grep some to see if there's more similar fail.