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authorGravatar Linus Torvalds <torvalds@linux-foundation.org> 2024-05-19 14:02:03 -0700
committerGravatar Linus Torvalds <torvalds@linux-foundation.org> 2024-05-19 14:02:03 -0700
commiteb6a9339efeb6f3d2b5c86fdf2382cdc293eca2c (patch)
tree3b0f8e71aec70c38cd0fda3f557e3f76a5f644a5 /Documentation
parentMerge tag 'bcachefs-2024-05-19' of https://evilpiepirate.org/git/bcachefs (diff)
parentfs/proc: fix softlockup in __read_vmcore (diff)
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Merge tag 'mm-nonmm-stable-2024-05-19-11-56' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
Pull non-mm updates from Andrew Morton: "Mainly singleton patches, documented in their respective changelogs. Notable series include: - Some maintenance and performance work for ocfs2 in Heming Zhao's series "improve write IO performance when fragmentation is high". - Some ocfs2 bugfixes from Su Yue in the series "ocfs2 bugs fixes exposed by fstests". - kfifo header rework from Andy Shevchenko in the series "kfifo: Clean up kfifo.h". - GDB script fixes from Florian Rommel in the series "scripts/gdb: Fixes for $lx_current and $lx_per_cpu". - After much discussion, a coding-style update from Barry Song explaining one reason why inline functions are preferred over macros. The series is "codingstyle: avoid unused parameters for a function-like macro"" * tag 'mm-nonmm-stable-2024-05-19-11-56' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: (62 commits) fs/proc: fix softlockup in __read_vmcore nilfs2: convert BUG_ON() in nilfs_finish_roll_forward() to WARN_ON() scripts: checkpatch: check unused parameters for function-like macro Documentation: coding-style: ask function-like macros to evaluate parameters nilfs2: use __field_struct() for a bitwise field selftests/kcmp: remove unused open mode nilfs2: remove calls to folio_set_error() and folio_clear_error() kernel/watchdog_perf.c: tidy up kerneldoc watchdog: allow nmi watchdog to use raw perf event watchdog: handle comma separated nmi_watchdog command line nilfs2: make superblock data array index computation sparse friendly squashfs: remove calls to set the folio error flag squashfs: convert squashfs_symlink_read_folio to use folio APIs scripts/gdb: fix detection of current CPU in KGDB scripts/gdb: make get_thread_info accept pointers scripts/gdb: fix parameter handling in $lx_per_cpu scripts/gdb: fix failing KGDB detection during probe kfifo: don't use "proxy" headers media: stih-cec: add missing io.h media: rc: add missing io.h ...
Diffstat (limited to 'Documentation')
-rw-r--r--Documentation/admin-guide/kdump/kdump.rst8
-rw-r--r--Documentation/admin-guide/kernel-parameters.txt5
-rw-r--r--Documentation/dev-tools/checkpatch.rst14
-rw-r--r--Documentation/process/coding-style.rst23
4 files changed, 44 insertions, 6 deletions
diff --git a/Documentation/admin-guide/kdump/kdump.rst b/Documentation/admin-guide/kdump/kdump.rst
index 0302a93b1d40..5376890adbeb 100644
--- a/Documentation/admin-guide/kdump/kdump.rst
+++ b/Documentation/admin-guide/kdump/kdump.rst
@@ -136,10 +136,6 @@ System kernel config options
CONFIG_KEXEC_CORE=y
- Subsequently, CRASH_CORE is selected by KEXEC_CORE::
-
- CONFIG_CRASH_CORE=y
-
2) Enable "sysfs file system support" in "Filesystem" -> "Pseudo
filesystems." This is usually enabled by default::
@@ -168,6 +164,10 @@ Dump-capture kernel config options (Arch Independent)
CONFIG_CRASH_DUMP=y
+ And this will select VMCORE_INFO and CRASH_RESERVE::
+ CONFIG_VMCORE_INFO=y
+ CONFIG_CRASH_RESERVE=y
+
2) Enable "/proc/vmcore support" under "Filesystems" -> "Pseudo filesystems"::
CONFIG_PROC_VMCORE=y
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 90f79a285427..ef25e06ec08c 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -3787,10 +3787,12 @@
Format: [state][,regs][,debounce][,die]
nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
- Format: [panic,][nopanic,][num]
+ Format: [panic,][nopanic,][rNNN,][num]
Valid num: 0 or 1
0 - turn hardlockup detector in nmi_watchdog off
1 - turn hardlockup detector in nmi_watchdog on
+ rNNN - configure the watchdog with raw perf event 0xNNN
+
When panic is specified, panic when an NMI watchdog
timeout occurs (or 'nopanic' to not panic on an NMI
watchdog, if CONFIG_BOOTPARAM_HARDLOCKUP_PANIC is set)
@@ -7507,4 +7509,3 @@
memory, and other data can't be written using
xmon commands.
off xmon is disabled.
-
diff --git a/Documentation/dev-tools/checkpatch.rst b/Documentation/dev-tools/checkpatch.rst
index 127968995847..a9fac978a525 100644
--- a/Documentation/dev-tools/checkpatch.rst
+++ b/Documentation/dev-tools/checkpatch.rst
@@ -906,6 +906,20 @@ Macros, Attributes and Symbols
See: https://lore.kernel.org/lkml/1399671106.2912.21.camel@joe-AO725/
+ **MACRO_ARG_UNUSED**
+ If function-like macros do not utilize a parameter, it might result
+ in a build warning. We advocate for utilizing static inline functions
+ to replace such macros.
+ For example, for a macro such as the one below::
+
+ #define test(a) do { } while (0)
+
+ there would be a warning like below::
+
+ WARNING: Argument 'a' is not used in function-like macro.
+
+ See: https://www.kernel.org/doc/html/latest/process/coding-style.html#macros-enums-and-rtl
+
**SINGLE_STATEMENT_DO_WHILE_MACRO**
For the multi-statement macros, it is necessary to use the do-while
loop to avoid unpredictable code paths. The do-while loop helps to
diff --git a/Documentation/process/coding-style.rst b/Documentation/process/coding-style.rst
index 9c7cf7347394..7e768c65aa92 100644
--- a/Documentation/process/coding-style.rst
+++ b/Documentation/process/coding-style.rst
@@ -827,6 +827,29 @@ Macros with multiple statements should be enclosed in a do - while block:
do_this(b, c); \
} while (0)
+Function-like macros with unused parameters should be replaced by static
+inline functions to avoid the issue of unused variables:
+
+.. code-block:: c
+
+ static inline void fun(struct foo *foo)
+ {
+ }
+
+Due to historical practices, many files still employ the "cast to (void)"
+approach to evaluate parameters. However, this method is not advisable.
+Inline functions address the issue of "expression with side effects
+evaluated more than once", circumvent unused-variable problems, and
+are generally better documented than macros for some reason.
+
+.. code-block:: c
+
+ /*
+ * Avoid doing this whenever possible and instead opt for static
+ * inline functions
+ */
+ #define macrofun(foo) do { (void) (foo); } while (0)
+
Things to avoid when using macros:
1) macros that affect control flow: