On Fri, Apr 20, 2007 at 09:08:36PM +0400, Oleg Nesterov wrote: > On 04/20, Jarek Poplawski wrote: > > > > On Thu, Apr 19, 2007 at 02:21:22PM +0400, Oleg Nesterov wrote: > > ... > > > Yes. It would be better to use cancel_work_sync() instead of > > > flush_workqueue() > > > to make this less possible (because cancel_work_sync() doesn't need to > > > wait for > > > the whole ->worklist), but we can't. > > > > > > > Maybe this patch could check, if I'm not dreaming... > > > > > > Also: cancel_rearming_delayed_work() will hang if it (or > > > cancel_delayed_work()) > > > was already called. > > > > > > I had some ideas how to make this interface reliable, but I can't see how > > > to do > > > this without uglification of the current code. > > > > For some time I thought about using a flag (isn't there > > one available after NOAUTOREL?), e.g. WORK_STRUCT_CANCEL, > > as a sign: > > > > - for a workqueue code: that the work shouldn't be queued, > > nor executed, if possiblei, at first possible check. > > Well, yes and no, afaics. (note also that NOAUTOREL has already gone).
I thought I wrote the same (sorry for my English)... > > First, this flag should be cleared after return from > cancel_rearming_delayed_work(). I think this flag, if at all, probably should be cleared only consciously by the owner of a work, maybe as a schedule_xxx_work parameter, (but shouldn't be used from work handlers for rearming). Mostly it should mean: we are closing (and have no time to chase our work)... > Also, we should add a lot of nasty checks to workqueue.c Checking a flag isn't nasty - it's clear. IMHO current way of checking, whether cancel succeeded, is nasty. > > I _think_ we can re-use WORK_STRUCT_PENDING to improve this interface. > Note that if we set WORK_STRUCT_PENDING, the work can't be queued, and > dwork->timer can't be started. The only problem is that it is not so > trivial to avoid races. If there were no place, it would be better, then current way. But WORK_STRUCT_PENDING couldn't be used for some error checking, as it's now. > > I'll try to do something on Sunday. > > > - for a work function: to stop execution as soon as possible, > > even without completing the usual job, at first possible check. > > I doubt we need this "in general". It is easy to add some flag to the > work_struct's container and check it in work->func() when needed. Yes, but currently you cannot to behave like this e.g. with "rearming" work. And maybe a common api could save some work. But of course, if you have better way to assure this, it's OK with me and congratulations! Regards, Jarek P. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/