Messages in this thread | | | Subject | Re: [PATCH v4 1/2] SCSI: Asynchronous event notification infrastructure | From | James Bottomley <> | Date | Mon, 29 Oct 2007 11:17:07 -0500 |
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On Mon, 2007-10-29 at 12:07 -0400, Jeff Garzik wrote: > James Bottomley wrote: > > This still doesn't solve the fundamental corruption problem: > > sdev->event_work has to contain the work entry until the workqueue has > > finished executing it (which is some unspecified time in the future). > > As soon as you drop the sdev->list_lock, the system thinks > > sdev->event_work is available for reuse. If we fire another event > > before the work queue finished processing the prior event, the queue > > will be corrupted. > > I think you're misunderstanding the workqueue code? You can call > schedule_work(&sdev->event_work) from anywhere, any time you like, as > many times as you like.
OK, take me through it slowly then ... I think schedule_work(work) inserts work->entry onto the workqueue list (in workqueue.c:insert_work()). If the event hasn't fired, it will already be on the list, so adding the same entry to a list twice causes a list corruption problem.
Plus, unfortunately, the CC/UA events are going to have to carry extra sense data; they're not simply going to be triggers saying something happened.
James
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