kernel/linux.git/include/asm-generic/percpu.h, branch v6.19.11

asm-generic: percpu: Add assembly guard

2025-10-27T15:41:53+00:00

Currently, asm/percpu.h is directly or indirectly included by some assembly files on x86. Some of them (e.g., checksum_32.S) are also used on um. But x86 and um provide different versions of asm/percpu.h -- um uses asm-generic/percpu.h directly. When SMP is enabled, asm-generic/percpu.h will introduce C code that cannot be assembled. Since asm-generic/percpu.h currently is not designed for use in assembly, and these assembly files do not actually need asm/percpu.h on um, let's add the assembly guard in asm-generic/percpu.h to fix this issue. Cc: Arnd Bergmann Cc: linux-arch@vger.kernel.org Signed-off-by: Tiwei Bie Acked-by: Arnd Bergmann Link: https://patch.msgid.link/20251027001815.1666872-8-tiwei.bie@linux.dev Signed-off-by: Johannes Berg

percpu: repurpose __percpu tag as a named address space qualifier

2025-03-17T05:05:53+00:00

The patch introduces __percpu_qual define and repurposes __percpu tag as a named address space qualifier using the new define. Arches can now conditionally define __percpu_qual as their named address space qualifier for percpu variables. Link: https://lkml.kernel.org/r/20250127160709.80604-6-ubizjak@gmail.com Signed-off-by: Uros Bizjak Acked-by: Nadav Amit Cc: Arnd Bergmann Cc: Thomas Gleixner Cc: Dennis Zhou Cc: Tejun Heo Cc: Christoph Lameter Cc: Linus Torvalds Cc: Andy Lutomirski Cc: Ingo Molnar Cc: Brian Gerst Cc: "H. Peter Anvin" Cc: Peter Zijlstra Cc: Boqun Feng Cc: Borislav Petkov Cc: Dave Hansen Cc: "David S. Miller" Cc: Denys Vlasenko Cc: Eric Dumazet Cc: Jakub Kicinski Cc: Kent Overstreet Cc: Paolo Abeni Cc: Waiman Long Cc: Will Deacon Signed-off-by: Andrew Morton

percpu: use TYPEOF_UNQUAL() in variable declarations

2025-03-17T05:05:53+00:00

Use TYPEOF_UNQUAL() to declare variables as a corresponding type without named address space qualifier to avoid "`__seg_gs' specified for auto variable `var'" errors. Link: https://lkml.kernel.org/r/20250127160709.80604-4-ubizjak@gmail.com Signed-off-by: Uros Bizjak Acked-by: Nadav Amit Acked-by: Christoph Lameter Cc: Dennis Zhou Cc: Tejun Heo Cc: Andy Lutomirski Cc: Thomas Gleixner Cc: Ingo Molnar Cc: Borislav Petkov Cc: Dave Hansen Cc: "H. Peter Anvin" Cc: Kent Overstreet Cc: Arnd Bergmann Cc: "David S. Miller" Cc: Eric Dumazet Cc: Jakub Kicinski Cc: Paolo Abeni Cc: Peter Zijlstra Cc: Will Deacon Cc: Waiman Long Cc: Boqun Feng Cc: Linus Torvalds Cc: Brian Gerst Cc: Denys Vlasenko Signed-off-by: Andrew Morton

percpu: Fix self-assignment of __old in raw_cpu_generic_try_cmpxchg()

2023-06-08T08:28:39+00:00

After commit c5c0ba953b8c ("percpu: Add {raw,this}_cpu_try_cmpxchg()"), clang built ARCH=arm and ARCH=arm64 kernels with CONFIG_INIT_STACK_NONE started panicking on boot in alloc_vmap_area(): [ 0.000000] kernel BUG at mm/vmalloc.c:1638! [ 0.000000] Internal error: Oops - BUG: 00000000f2000800 [#1] PREEMPT SMP [ 0.000000] Modules linked in: [ 0.000000] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 6.4.0-rc2-ARCH+ #1 [ 0.000000] Hardware name: linux,dummy-virt (DT) [ 0.000000] pstate: 200000c9 (nzCv daIF -PAN -UAO -TCO -DIT -SSBS BTYPE=--) [ 0.000000] pc : alloc_vmap_area+0x7ec/0x7f8 [ 0.000000] lr : alloc_vmap_area+0x7e8/0x7f8 Compiling mm/vmalloc.c with W=2 reveals an instance of -Wshadow, which helps uncover that through macro expansion, '__old = *(ovalp)' in raw_cpu_generic_try_cmpxchg() can become '__old = *(&__old)' through raw_cpu_generic_cmpxchg(), which results in garbage being assigned to the inner __old and the cmpxchg not working properly. Add an extra underscore to __old in raw_cpu_generic_try_cmpxchg() so that there is no more self-assignment, which resolves the panics. Closes: https://github.com/ClangBuiltLinux/linux/issues/1868 Fixes: c5c0ba953b8c ("percpu: Add {raw,this}_cpu_try_cmpxchg()") Debugged-by: Nick Desaulniers Signed-off-by: Nathan Chancellor Signed-off-by: Peter Zijlstra (Intel) Link: https://lkml.kernel.org/r/20230607-fix-shadowing-in-raw_cpu_generic_try_cmpxchg-v1-1-8f0a3d930d43@kernel.org

arch: Remove cmpxchg_double

2023-06-05T07:36:39+00:00

No moar users, remove the monster. Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Arnd Bergmann Reviewed-by: Mark Rutland Acked-by: Heiko Carstens Tested-by: Mark Rutland Link: https://lore.kernel.org/r/20230531132323.991907085@infradead.org

percpu: Wire up cmpxchg128

2023-06-05T07:36:37+00:00

In order to replace cmpxchg_double() with the newly minted cmpxchg128() family of functions, wire it up in this_cpu_cmpxchg(). Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Mark Rutland Tested-by: Mark Rutland Link: https://lore.kernel.org/r/20230531132323.654945124@infradead.org

percpu: Add {raw,this}_cpu_try_cmpxchg()

2023-06-05T07:36:36+00:00

Add the try_cmpxchg() form to the per-cpu ops. Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Mark Rutland Tested-by: Mark Rutland Link: https://lore.kernel.org/r/20230531132323.587480729@infradead.org

asm-generic: percpu: avoid Wshadow warning

2020-10-26T23:54:48+00:00

Nesting macros that use the same local variable names causes warnings when building with "make W=2": include/asm-generic/percpu.h:117:14: warning: declaration of '__ret' shadows a previous local [-Wshadow] include/asm-generic/percpu.h:126:14: warning: declaration of '__ret' shadows a previous local [-Wshadow] These are fairly harmless, but since the warning comes from a global header, the warning happens every time the headers are included, which is fairly annoying. Rename the variables to avoid shadowing and shut up the warning. Signed-off-by: Arnd Bergmann Reviewed-by: Luc Van Oostenryck Signed-off-by: Dennis Zhou

percpu: fix __percpu annotation in asm-generic

2020-01-31T19:15:59+00:00

The generic implementation of raw_cpu_generic_add_return() is: #define raw_cpu_generic_add_return(pcp, val) \ ({ \ typeof(&(pcp)) __p = raw_cpu_ptr(&(pcp)); \ \ *__p += val; \ *__p; \ }) where the 'pcp' argument is a __percpu lvalue. There, the variable '__p' is declared as a __percpu pointer the type of the address of 'pcp') but: 1) the value assigned to it, the return value of raw_cpu_ptr(), is a plain (__kernel) pointer, not a __percpu one. 2) this variable is dereferenced just after while a __percpu pointer is implicitly __noderef. So, fix the declaration of the 'pcp' variable to its correct type: the plain (non-percpu) pointer corresponding to pcp's address, using the fact that typeof() ignores the address space and the 'noderef' attribute of its agument. Same for raw_cpu_generic_xchg(), raw_cpu_generic_cmpxchg() & raw_cpu_generic_cmpxchg_double(). This removes 209 warnings on ARM, 525 on ARM64, 220 on x86 & more than 2600 on ppc64 (all of them with the default config). Cc: Tejun Heo Cc: Nicholas Piggin Reported-by: Ben Dooks Signed-off-by: Luc Van Oostenryck Acked-by: Christoph Lameter Signed-off-by: Dennis Zhou

percpu: remove PER_CPU_DEF_ATTRIBUTES macro

2018-10-31T15:54:14+00:00

The macro is not used: $ grep -r PER_CPU_DEF_ATTRIBUTES include/linux/percpu-defs.h: __PCPU_ATTRS(sec) PER_CPU_DEF_ATTRIBUTES __weak \ include/linux/percpu-defs.h: __PCPU_ATTRS(sec) PER_CPU_DEF_ATTRIBUTES \ include/asm-generic/percpu.h:#ifndef PER_CPU_DEF_ATTRIBUTES include/asm-generic/percpu.h:#define PER_CPU_DEF_ATTRIBUTES It was added with b01e8dc34379 ("alpha: fix percpu build breakage") and removed in 2009 with b01e8dc34379..6088464cf1ae. Link: http://lkml.kernel.org/r/20180821164904.qqhcduimjznods66@K55DR.localdomain Signed-off-by: Alexander Pateenok Acked-by: Tejun Heo Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds