Re: syncing the disks when entering sleep

[Nigel Cunningham <ncunningham@crca.org.au>]

Hi.

Rafael J. Wysocki wrote:
> On Thursday 11 February 2010, Pavel Machek wrote:
>>>> Really? If so then it is misdesigned.
>>>>
>>>> Before the "don't sync" proposal, it was okay to have multiple
>>>> power managers.
>>>>
>>>> Actually I have three on zaurus. There's in-kernel suspend on battery
>>>> critical, then there's somehing userspace in desktop environment, and
>>>> then I'm triggering suspends by hand using echo.
>>> To be precise, 1 and 3 are things that override the power manager.
>>>
>>> And if you override the power manager, you're supposed to know what you're
>>> doing, aren't you?
>> I know what I'm doing, but I'd prefer traps not being set for me.
> 
> What are you talking about?  Either you set the knob or you don't.  If you
> don't, nothing changes.
> 
>>>>> So really, I don't see anything wrong with a knob that will turn the kernel
>>>>> sync off entirely, because that basically means "my user space is
>>>>> not broken".
>>>> Because, very easily, parts of my users space may be broken.
>>> How exactly would they be broken?
>> I have 3 power managers.
> 
> You don't.
> 
>> You called that broken before.
> 
> Because it is so.  Think about user space suspend hooks, for example, like
> s2ram.  Surely your kernel emergency suspend can't use anything like this?
> 
>> How is power manager expected to work on zaurus, which suspends from
>> kernel on battery critical? echo no > sync; sync; echo mem > state;
>> echo yes > sync?
>>
>> Its still racy..
> 
> Please refer to my reply to Oliver.
> 
>>> Why don't we just assume that the user who sets the knob knows what he's doing?
>>>
>> Because better alternatives exist. Like 'echo mem:nosync > state'.
> 
> That is a sledgehammer.
> 
> I really don't understand your objections here and none of the "alternatives"
> you've been talking about so far would be acceptable to me.

I'm in violent agreement with Rafael. Pavel, I think you're overruled on
this one.

Regards,

Nigel