Greg Kroah-Hartman
598cf27219
Link: https://lore.kernel.org/r/20260217200002.683975158@linuxfoundation.org Tested-by: Florian Fainelli <florian.fainelli@broadcom.com> Tested-by: Takeshi Ogasawara <takeshi.ogasawara@futuring-girl.com> Tested-by: Peter Schneider <pschneider1968@googlemail.com> Tested-by: Jon Hunter <jonathanh@nvidia.com> Tested-by: Salvatore Bonaccorso <carnil@debian.org> Tested-by: Brett A C Sheffield <bacs@librecast.net> Tested-by: Mark Brown <broonie@kernel.org> Tested-by: Luna Jernberg <droidbittin@gmail.com> Tested-by: Ronald Warsow <rwarsow@gmx.de> Tested-by: Justin M. Forbes <jforbes@fedoraproject.org> Tested-by: Ron Economos <re@w6rz.net> Tested-by: Miguel Ojeda <ojeda@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
54 lines
1.7 KiB
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54 lines
1.7 KiB
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.. 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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