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39ce15a48f
Somehow CONFIG_PSTORE_FIRMWARE ended up in this document when I intended
it to be CONFIG_CHROMEOS_PSTORE. Correct the configuration option and
make it clear that not all options are required.
Fixes: b1f02f005a ("Documentation: power: Add document on debugging shutdown hangs")
Reported-by: Rodrigo Siqueira <siqueira@igalia.com>
Signed-off-by: Mario Limonciello (AMD) <superm1@kernel.org>
[ rjw: Fixes: tag ]
Link: https://patch.msgid.link/20251106142524.3841343-1-superm1@kernel.org
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
54 lines
1.7 KiB
ReStructuredText
54 lines
1.7 KiB
ReStructuredText
.. SPDX-License-Identifier: GPL-2.0
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Debugging Kernel Shutdown Hangs with pstore
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+++++++++++++++++++++++++++++++++++++++++++
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Overview
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========
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If the system hangs while shutting down, the kernel logs may need to be
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retrieved to debug the issue.
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On systems that have a UART available, it is best to configure the kernel to use
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this UART for kernel console output.
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If a UART isn't available, the ``pstore`` subsystem provides a mechanism to
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persist this data across a system reset, allowing it to be retrieved on the next
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boot.
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Kernel Configuration
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====================
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To enable ``pstore`` and enable saving kernel ring buffer logs, set the
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following kernel configuration options:
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* ``CONFIG_PSTORE=y``
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* ``CONFIG_PSTORE_CONSOLE=y``
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Additionally, enable a backend to store the data. Depending upon your platform
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some potential options include:
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* ``CONFIG_EFI_VARS_PSTORE=y``
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* ``CONFIG_PSTORE_RAM=y``
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* ``CONFIG_CHROMEOS_PSTORE=y``
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* ``CONFIG_PSTORE_BLK=y``
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Kernel Command-line Parameters
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==============================
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Add these parameters to your kernel command line:
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* ``printk.always_kmsg_dump=Y``
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* Forces the kernel to dump the entire message buffer to pstore during
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shutdown
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* ``efi_pstore.pstore_disable=N``
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* For EFI-based systems, ensures the EFI backend is active
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Userspace Interaction and Log Retrieval
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=======================================
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On the next boot after a hang, pstore logs will be available in the pstore
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filesystem (``/sys/fs/pstore``) and can be retrieved by userspace.
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On systemd systems, the ``systemd-pstore`` service will help do the following:
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#. Locate pstore data in ``/sys/fs/pstore``
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#. Read and save it to ``/var/lib/systemd/pstore``
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#. Clear pstore data for the next event
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