Re: Overview of concurrency managed workqueue

[Tejun Heo]

On 06/16/2010 03:37 PM, Johannes Berg wrote:
>> As multiple execution contexts are available for each wq, deadlocks
>> around execution contexts is much harder to create.  The default
>> workqueue, system_wq, has maximum concurrency level of 256 and unless
>> there is a use case which can result in a dependency loop involving
>> more than 254 workers, it won't deadlock.
> 
> I see a lot of stuff about the current limitations etc., but nothing
> about code that actually _relies_ on the synchronisation properties of
> the current wqs. We talked about that a long time ago, is it still
> guaranteed that a single-threaded wq will serialise all work put onto
> it? It needs to be, but I don't see you explicitly mentioning it.

Oh yeah, if you have WQ_SINGLE_CPU + max inflight of 1, works on the
wq are fully ordered.

-- 
tejun
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