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.
Also, I think Kristin's initial use of execute_in_user_context() was a
good call .. if we already have a user context, there's no need to
bother the workqueue ... some of these events will likely trigger from
thread backed kernel daemons.
Quite agreed that sdev_evt_notify() might be called from kernel daemons,
but in general this is a fire-and-forget API that is -likely- to be
called from interrupt or completion context of many drivers, just like
scsi_done or other completion APIs. It is a fundamentally parallel
interface.
If thread-backed kernel daemons want to use this, it is trivial for them
to schedule work, then sync.
Jeff
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