67 lines
2.7 KiB
Diff
67 lines
2.7 KiB
Diff
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From 21e0afbe2764476c98d7809af6634773835723d4 Mon Sep 17 00:00:00 2001
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From: Kairui Song <kasong@redhat.com>
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Date: Tue, 4 Aug 2020 17:30:51 +0800
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Subject: [PATCH] pstore: don't enable crash_kexec_post_notifiers by default
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commit f00c36641a253f4ea659ec3def5d87ba1336eb3b enabled
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crash_kexec_post_notifiers by default regardless of whether pstore
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is enabled or not.
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The original intention to enabled this option by default is that
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it only affects kernel post-panic behavior, so should have no harm.
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But this is not true if the user wants a reliable kdump.
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crash_kexec_post_notifiers is known to cause problem with kdump,
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and it's documented in kernel. It's not easy to fix the problem
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because of how kdump works. Kdump expects the crashed kernel to
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jump to an pre-loaded crash kernel, so doing any extra job before
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the jump will increase the risk.
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It depends on the user to choose between having a reliable kdump or
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some other post-panic debug mechanic.
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So it's better to keep this config untouched by default, or it may put
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kdump at higher risk of failing silently. User should enable it by
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uncommenting the config line manually if pstore is always needed.
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Also add a inline comment inform user about the potential issue.
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Thanks to Dave Young for finding out this issue.
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Fixes #16661
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Signed-off-by: Kairui Song <kasong@redhat.com>
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(cherry picked from commit edb8c98446e7dae54bcda90806bf6c068e1c6385)
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Related: #2211416
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---
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tmpfiles.d/systemd-pstore.conf | 11 ++++++++---
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1 file changed, 8 insertions(+), 3 deletions(-)
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diff --git a/tmpfiles.d/systemd-pstore.conf b/tmpfiles.d/systemd-pstore.conf
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index 8b6a1dafc3..e8e9ed48ae 100644
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--- a/tmpfiles.d/systemd-pstore.conf
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+++ b/tmpfiles.d/systemd-pstore.conf
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@@ -11,8 +11,13 @@
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# control writes into pstore.
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#
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# The crash_kexec_post_notifiers parameter enables the kernel to write
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-# dmesg (including stack trace) into pstore upon a panic, and
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-# printk.always_kmsg_dump parameter enables the kernel to write dmesg
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+# dmesg (including stack trace) into pstore upon a panic even if kdump
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+# is loaded, only needed if you want to use pstore with kdump. Without
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+# this parameter, kdump could block writing to pstore for stability
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+# reason. Note this increases the risk of kdump failure even if pstore
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+# is not available.
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+#
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+# The printk.always_kmsg_dump parameter enables the kernel to write dmesg
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# upon a normal shutdown (shutdown, reboot, halt).
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#
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# To configure the kernel parameters, uncomment the appropriate
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@@ -26,4 +31,4 @@
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d /var/lib/systemd/pstore 0755 root root 14d
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#w- /sys/module/printk/parameters/always_kmsg_dump - - - - Y
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-w- /sys/module/kernel/parameters/crash_kexec_post_notifiers - - - - Y
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+#w- /sys/module/kernel/parameters/crash_kexec_post_notifiers - - - - Y
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