x86/amd_node: Fix PCI device reference counting in amd_smn_init()grafted

The local "root" pointer is a temporary variable used during the device
search. Therefore, refcount related to the search iterators should be cleaned
up after the search is complete.

Use the __free() cleanup macro to ensure the refcount is decremented when the
temporary pointer goes out of scope.

Additionally, increment the refcount when caching a root pointer. This ensures
the in-use refcount is separate from the temporary search refcounting.

Finally, drop the redundant "root = NULL" before the second search loop. The
pci_get_class() iterator always decrements the refcount of its "from"
argument, so the first loop can only fall through with "root" already NULL.

Fixes: 0a4b61d9c2e4 ("x86/amd_node: Fix AMD root device caching")
Closes: https://sashiko.dev/#/patchset/20260806160159.230453-1-jason.andryuk%40amd.com
Reported-by: Sashiko <sashiko-bot@kernel.org>
Assisted-by: LLM
Signed-off-by: Yazen Ghannam <yazen.ghannam@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Mario Limonciello (AMD) <superm1@kernel.org>
Cc: <stable@kernel.org>
Link: https://patch.msgid.link/20260903154325.74343-1-yazen.ghannam@amd.com

1 files changed, 52 insertions, 0 deletions

diff --git a/Documentation/admin-guide/sysctl/debug.rst b/Documentation/admin-guide/sysctl/debug.rst
new file mode 100644
index 000000000..506bd5e48
--- /dev/null
+++ b/Documentation/admin-guide/sysctl/debug.rst
@@ -0,0 +1,52 @@
+================
+/proc/sys/debug/
+================
+
+These files show up in ``/proc/sys/debug/``, depending on the
+kernel configuration:
+
+.. contents:: :local:
+
+exception-trace
+===============
+
+This flag controls whether the kernel prints information about unhandled
+signals (like segmentation faults) to the kernel log (``dmesg``).
+
+- ``0``: Unhandled signals are not traced.
+- ``1``: Information about unhandled signals is printed.
+
+The default value is ``1`` on most architectures (like x86, MIPS, RISC-V),
+but it is ``0`` on **arm64**.
+
+The actual information printed and the context provided varies
+significantly depending on the CPU architecture. For example:
+
+- On **x86**, it typically prints the instruction pointer (IP), error
+  code, and address that caused a page fault.
+- On **PowerPC**, it may print the next instruction pointer (NIP),
+  link register (LR), and other relevant registers.
+
+When enabled, this feature is often rate-limited to prevent the kernel
+log from being flooded during a crash loop.
+
+kprobes-optimization
+====================
+
+This flag enables or disables the optimization of Kprobes on certain
+architectures (like x86).
+
+- ``0``: Kprobes optimization is turned off.
+- ``1``: Kprobes optimization is turned on (default).
+
+For more details on Kprobes and its optimization, please refer to
+Documentation/trace/kprobes.rst.
+
+Copyright (c) 2026, Shubham Chakraborty <chakrabortyshubham66@gmail.com>
+
+For general info and legal blurb, please look in
+Documentation/admin-guide/sysctl/index.rst.
+
+.. See scripts/check-sysctl-docs to keep this up to date:
+.. scripts/check-sysctl-docs -vtable="debug" \
+..         $(git grep -l register_sysctl_)