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percpu: drop CONFIG_DEBUG_FORCE_WEAK_PER_CPU

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alpha requires percpu variables in modules to be defined as weak so that the
compiler generates GOT based external references for them. This puts two
extra restrictions on percpu variable definitions. The symbol must be
globally unique even when static and a static percpu variable can't be
defined inside a function. DEBUG_FORCE_WEAK_PER_CPU exists to give generic
code build coverage for these restrictions without building for alpha.

MEM_ALLOC_PROFILING defines a static percpu counter at each allocation call
site and thus can't be built with weak percpu definitions, so it depends on
!DEBUG_FORCE_WEAK_PER_CPU. As allmodconfig enables DEBUG_FORCE_WEAK_PER_CPU,
this knocks MEM_ALLOC_PROFILING out of allmodconfig build coverage.

allmodconfig coverage for MEM_ALLOC_PROFILING is worth more than build
coverage for restrictions which only matter to alpha module builds. Drop
DEBUG_FORCE_WEAK_PER_CPU. Restriction violations will now show up only on
alpha builds.

Link: https://lore.kernel.org/178656406317.2437052.7257990869957704195@slm.duckdns.org
Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Suren Baghdasaryan <surenb@google.com>
Acked-by: Gabriele Monaco <gmonaco@redhat.com>	[include/rv/da_monitor.h]
Cc: Dennis Zhou <dennis@kernel.org>
Cc: Kent Overstreet <kent.overstreet@linux.dev>
Cc: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Tejun Heo
2026-08-12 09:47:43 -10:00
committed by Andrew Morton
parent f7e698e326
commit f525001b33
4 changed files with 2 additions and 23 deletions
Download Patch File Download Diff File Expand all files Collapse all files

7
include/linux/percpu-defs.h
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@@ -65,13 +65,8 @@
*
* Archs which need weak percpu definitions should set
* CONFIG_ARCH_MODULE_NEEDS_WEAK_PER_CPU when necessary.
*
* To ensure that the generic code observes the above two
* restrictions, if CONFIG_DEBUG_FORCE_WEAK_PER_CPU is set weak
* definition is used for all cases.
*/
#if (defined(CONFIG_ARCH_MODULE_NEEDS_WEAK_PER_CPU) && defined(MODULE)) || \
defined(CONFIG_DEBUG_FORCE_WEAK_PER_CPU)
#if defined(CONFIG_ARCH_MODULE_NEEDS_WEAK_PER_CPU) && defined(MODULE)
/*
* __pcpu_scope_* dummy variable is used to enforce scope. It
* receives the static modifier when it's used in front of

2
include/rv/da_monitor.h
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@@ -24,7 +24,7 @@
/*
* Per-cpu variables require a unique name although static in some
* configurations (e.g. CONFIG_DEBUG_FORCE_WEAK_PER_CPU or alpha modules).
* configurations (e.g. alpha modules).
*/
#define DA_MON_NAME CONCATENATE(da_mon_, MONITOR_NAME)

15
lib/Kconfig.debug
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@@ -613,21 +613,6 @@ config BUILTIN_MODULE_RANGES
It also records an anchor symbol to determine the load address of the
section.
config DEBUG_FORCE_WEAK_PER_CPU
bool "Force weak per-cpu definitions"
depends on DEBUG_KERNEL
help
s390 and alpha require percpu variables in modules to be
defined weak to work around addressing range issue which
puts the following two restrictions on percpu variable
definitions.
1. percpu symbols must be unique whether static or not
2. percpu variables can't be defined inside a function
To ensure that generic code follows the above rules, this
option forces all percpu variables to be defined as weak.
config WARN_CONTEXT_ANALYSIS
bool "Compiler context-analysis warnings"
depends on CC_IS_CLANG && CLANG_VERSION >= 230000

1
mm/Kconfig.debug
View File

@@ -326,7 +326,6 @@ config MEM_ALLOC_PROFILING
default n
depends on MMU
depends on PROC_FS
depends on !DEBUG_FORCE_WEAK_PER_CPU
select CODE_TAGGING
select PAGE_EXTENSION
select SLAB_OBJ_EXT