kernel: work: fix race condition with cancel before work runs
The original state management solution involved separate locks for a
work queue and each work item. To avoid inter-lock dependencies a
window was left between the point where the work item was removed from
the queue (protected by queue lock) and the point where the work item
state was updated to mark the work item running.
This introduced a bug: If a cancellation was issued during this window
it would succeed, and the work item would appear to be idle even
though in fact the work queue thread was about to run it.
Since there is now only one lock, move the work item state updates
into the mutex regions associated with dequeuing the work item and
clearing the work queue busy flag.
Note that removing the window between queue and work mutex regions
eliminates the potential of having a dequeued work item be cancelled
before its QUEUED flag is cleared, simplifying the work item state
update.
Signed-off-by: Peter Bigot <peter.bigot@nordicsemi.no>
1 file changed
