ACPI: EC: Rework flushing of EC work while suspended to idle
The flushing of pending work in the EC driver uses drain_workqueue() to flush the event handling work that can requeue itself via advance_transaction(), but this is problematic, because that work may also be requeued from the query workqueue. Namely, if an EC transaction is carried out during the execution of a query handler, it involves calling advance_transaction() which may queue up the event handling work again. This causes the kernel to complain about attempts to add a work item to the EC event workqueue while it is being drained and worst-case it may cause a valid event to be skipped. To avoid this problem, introduce two new counters, events_in_progress and queries_in_progress, incremented when a work item is queued on the event workqueue or the query workqueue, respectively, and decremented at the end of the corresponding work function, and make acpi_ec_dispatch_gpe() the workqueues in a loop until the both of these counters are zero (or system wakeup is pending) instead of calling acpi_ec_flush_work(). At the same time, change __acpi_ec_flush_work() to call flush_workqueue() instead of drain_workqueue() to flush the event workqueue. While at it, use the observation that the work item queued in acpi_ec_query() cannot be pending at that time, because it is used only once, to simplify the code in there. Additionally, clean up a comment in acpi_ec_query() and adjust white space in acpi_ec_event_processor(). Fixes: f0ac20c3 ("ACPI: EC: Fix flushing of pending work") Signed-off-by:Rafael J. Wysocki <rafael.j.wysocki@intel.com>
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