http://bugzilla.kernel.org/show_bug.cgi?id=14668
Summary: Resume from disk hangs in acpi_ex_acquire_global_lock
Product: ACPI
Version: 2.5
Platform: All
OS/Version: Linux
Tree: Mainline
Status: NEW
Severity: normal
Priority: P1
Component: EC
AssignedTo: acpi...@kernel-bugs.osdl.org
ReportedBy: maximlevit...@gmail.com
CC: r...@sisk.pl
Regression: No
I found out that my system will occasionally fail when resuming from
hibernation.
Common denominator was that attempt to acquire global acpi lock failed.
According to the source, this lock is only used on access to fields of
'OperationRegion's that have 'Lock' attribute, or in other simpler words, this
lock protects access to device registers.
My notebook has:
OperationRegion (NVST, SystemMemory, 0x7FEBCE89, 0x00000063)
Field (NVST, AnyAcc, Lock, Preserve)
OperationRegion (RCRB, SystemMemory, 0xFED1C000, 0x4000)
Field (RCRB, DWordAcc, Lock, Preserve)
OperationRegion (ERAM, EmbeddedControl, 0x00, 0xFF)
Field (ERAM, ByteAcc, Lock, Preserve)
NVST is in memory, containing some bios flags. It is used in some places.
RCRB is a BAR of southbridge, and used I think for pcie hotplug.
I know that because I mapped all unknown memory ranges using intel docs.
(Southbridge/LPC configuration (Root Complex Base Address))
I don't thing that access to these registers hangs in the middle.
However, the last third register, looks very suspicions, 'cause its the EC.
In fact system hangs, while it tries to read from this range.
But it hangs because it can't take the lock, and I suspect that this is due to
access to same range.
So, ether global lock isn't released during suspend, or first attempt to touch
EC stalls.
Note that I don't see EC GPE storms warning anymore lately, so EC operates in
interrupt mode.
For testing, I removed this global lock, and then I did ~230 s2disk cycles,
using /sys/power/disk directly, and 'reboot' method.
Then, I did the full test that is ~130 cycles using 'platform' method,
pm_hibernate, and using rtc alarm to wake the system.
I couldn't make the system hang.
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