Messages in this thread | | | Subject | Re: [PATCH 2/2] scsi: don't use execute_in_process_context() | From | James Bottomley <> | Date | Tue, 14 Dec 2010 08:26:38 -0600 |
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On Tue, 2010-12-14 at 15:19 +0100, Tejun Heo wrote: > Hello, James. > > On 12/14/2010 03:09 PM, James Bottomley wrote: > > That's the point ... it's purely for operations which require user > > context which may not have it. There's no synchronisation by design > > (it's a simple API). > > Well, the problem is that you do require proper synchornization > anyway; otherwise, there is no way to make sure that the work is > finished before the SCSI module is about to be unloaded. Currently, > the code uses flush_scheduled_work() for this, which is going away > because the latency can grow arbitrarily large and the behavior is > dependent on completely unrelated work items. So, either we need to > add a separate flush interface for ew's, flush the work item inside > ew's or schedule them to a dedicated workqueue.
Depends what you're doing about the flush problem. The synchronisation is inherent in the use (we're holding a reference to the module within the executed code). The flush is to try to speed things up so the user doesn't get annoyed during rmmod. We don't need a sync, just an accelerator.
> >> So, unless there's a compelling reason, let's remove it. > > > > The open coding of if (in_atomic()) { do workqueue stuff } else > > { execute function } is rather bug prone (most people tend to do > > in_interrupt()). It's better to encapsulate it in an API. > > Compelling reason for it to exist. Why not just use work when you > need execution context and the caller might or might not have one?
Because it's completely lame to have user context and not use it.
> > It was in SCSI ... I got told to make it generic. > > Heh, yeah, that would feel quite silly. Sorry about that. :-) > > But, really, let's just remove it. At this point, we either need to > fortify the interface or remove it and given the current usage, I > think we're better off with the latter.
I really don't think the open coding is a good idea. It's complex and error prone; exactly the type of thing that should be in an API.
> If any pressing need arises, > we can always add a proper API with all the necessary bells and > whistles later.
James
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