path: root/kernel
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authorRafael J. Wysocki <>2020-02-11 10:07:43 +0100
committerRafael J. Wysocki <>2020-02-11 10:07:43 +0100
commitf0ac20c3f6137910c8a927953e8a92f5b3716166 (patch)
treefa6fee7a42157383dc31c66857718e1ea034402e /kernel
parentbb6d3fb354c5ee8d6bde2d576eb7220ea09862b9 (diff)
ACPI: EC: Fix flushing of pending work
Commit 016b87ca5c8c ("ACPI: EC: Rework flushing of pending work") introduced a subtle bug into the flushing of pending EC work while suspended to idle, which may cause the EC driver to fail to re-enable the EC GPE after handling a non-wakeup event (like a battery status change event, for example). The problem is that the work item flushed by flush_scheduled_work() in __acpi_ec_flush_work() may disable the EC GPE and schedule another work item expected to re-enable it, but that new work item is not flushed, so __acpi_ec_flush_work() returns with the EC GPE disabled and the CPU running it goes into an idle state subsequently. If all of the other CPUs are in idle states at that point, the EC GPE won't be re-enabled until at least one CPU is woken up by another interrupt source, so system wakeup events that would normally come from the EC then don't work. This is reproducible on a Dell XPS13 9360 in my office which sometimes stops reacting to power button and lid events (triggered by the EC on that machine) after switching from AC power to battery power or vice versa while suspended to idle (each of those switches causes the EC GPE to trigger for several times in a row, but they are not system wakeup events). To avoid this problem, it is necessary to drain the workqueue entirely in __acpi_ec_flush_work(), but that cannot be done with respect to system_wq, because work items may be added to it from other places while __acpi_ec_flush_work() is running. For this reason, make the EC driver use a dedicated workqueue for EC events processing (let that workqueue be ordered so that EC events are processed sequentially) and use drain_workqueue() on it in __acpi_ec_flush_work(). Fixes: 016b87ca5c8c ("ACPI: EC: Rework flushing of pending work") Cc: 5.4+ <> # 5.4+ Signed-off-by: Rafael J. Wysocki <>
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