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Lv Zheng 6b1f21a111 ACPI / EC: Work around method reentrancy limit in ACPICA for _Qxx ...

commit e1191bd4f6 upstream.

A regression is caused by the following commit:

  Commit: 02b771b64b
  Subject: ACPI / EC: Fix an issue caused by the serialized _Qxx evaluations

In this commit, using system workqueue causes that the maximum parallel
executions of _Qxx can exceed 255. This violates the method reentrancy
limit in ACPICA and generates the following error log:

  ACPI Error: Method reached maximum reentrancy limit (255) (20150818/dsmethod-341)

This patch creates a seperate workqueue and limits the number of parallel
_Qxx evaluations down to a configurable value (can be tuned against number
of online CPUs).

Since EC events are handled after driver probe, we can create the workqueue
in acpi_ec_init().

Fixes: 02b771b64b (ACPI / EC: Fix an issue caused by the serialized _Qxx evaluations)
Link: https://bugzilla.kernel.org/show_bug.cgi?id=135691
Reported-and-tested-by: Helen Buus <ubuntu@hbuus.com>
Signed-off-by: Lv Zheng <lv.zheng@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

2016-08-20 18:09:27 +02:00

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