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Slowackiego 173, 80-298 Gdansk - KRS 101882 - NIP 957-07-52-316 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20221222_034726_688371_6785FDEF X-CRM114-Status: GOOD ( 13.76 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Hi all, I hope there will be place for such tiny helper in kernel. Quick cocci analyze shows there is probably few thousands places where it could be useful. I am not sure who is good person to review/ack such patches, so I've used my intuition to construct to/cc lists, sorry for mistakes. This is the 2nd approach of the same idea, with comments addressed[0]. The helper is tiny and there are advices we can leave without it, so I want to present few arguments why it would be good to have it: 1. Code readability/simplification/number of lines: Real example from drivers/net/ethernet/mellanox/mlx5/core/esw/qos.c: - previous_min_rate = evport->qos.min_rate; - evport->qos.min_rate = min_rate; + previous_min_rate = __xchg(evport->qos.min_rate, min_rate); For sure the code is more compact, and IMHO more readable. 2. Presence of similar helpers in other somehow related languages/libs: a) Rust[1]: 'replace' from std::mem module, there is also 'take' helper (__xchg(&x, 0)), which is the same as private helper in i915 - fetch_and_zero, see latest patch. b) C++ [2]: 'exchange' from utility header. If the idea is OK there are still 2 qestions to answer: 1. Name of the helper, __xchg follows kernel conventions, but for me Rust names are also OK. 2. Where to put the helper: a) as in this patchset include/linux/non-atomic/xchg.h, proposed by Andy Shevchenko, b) include/linux/utils.h ? any better name? Some kind of container for simple helpers. Structure of the patchset: 17 patches releasing __xchg name from arch files 1 patch adding __xchg 1 patch adding users of __xchg Arnd thanks for convienient set of cross compilers, it was very helpful. So many words for so small helper :) [0]: https://lore.kernel.org/lkml/Y5OFSvaYbv4XCxhE@smile.fi.intel.com/T/ [1]: https://doc.rust-lang.org/std/mem/index.html [2]: https://en.cppreference.com/w/cpp/header/utility Regards Andrzej Andrzej Hajda (19): arch/alpha: rename internal name __xchg to __arch_xchg arch/arc: rename internal name __xchg to __arch_xchg arch/arm: rename internal name __xchg to __arch_xchg arch/arm64: rename internal name __xchg to __arch_xchg arch/hexagon: rename internal name __xchg to __arch_xchg arch/ia64: rename internal name __xchg to __arch_xchg arch/loongarch: rename internal name __xchg to __arch_xchg arch/m68k: rename internal name __xchg to __arch_xchg arch/mips: rename internal name __xchg to __arch_xchg arch/openrisc: rename internal name __xchg to __arch_xchg arch/parisc: rename internal name __xchg to __arch_xchg arch/powerpc: correct logged function names in xchg helpers arch/riscv: rename internal name __xchg to __arch_xchg arch/s390: rename internal name __xchg to __arch_xchg arch/sh: rename internal name __xchg to __arch_xchg arch/sparc: rename internal name __xchg to __arch_xchg arch/xtensa: rename internal name __xchg to __arch_xchg linux/include: add non-atomic version of xchg drm/i915/gt: use __xchg instead of internal helper arch/alpha/include/asm/cmpxchg.h | 6 +++--- arch/arc/include/asm/cmpxchg.h | 4 ++-- arch/arm/include/asm/cmpxchg.h | 4 ++-- arch/arm64/include/asm/cmpxchg.h | 4 ++-- arch/hexagon/include/asm/cmpxchg.h | 6 +++--- arch/ia64/include/asm/cmpxchg.h | 2 +- arch/ia64/include/uapi/asm/cmpxchg.h | 4 ++-- arch/loongarch/include/asm/cmpxchg.h | 4 ++-- arch/m68k/include/asm/cmpxchg.h | 6 +++--- arch/mips/include/asm/cmpxchg.h | 4 ++-- arch/openrisc/include/asm/cmpxchg.h | 4 ++-- arch/parisc/include/asm/cmpxchg.h | 4 ++-- arch/powerpc/include/asm/cmpxchg.h | 4 ++-- arch/riscv/include/asm/atomic.h | 2 +- arch/riscv/include/asm/cmpxchg.h | 4 ++-- arch/s390/include/asm/cmpxchg.h | 4 ++-- arch/sh/include/asm/cmpxchg.h | 4 ++-- arch/sparc/include/asm/cmpxchg_32.h | 4 ++-- arch/sparc/include/asm/cmpxchg_64.h | 4 ++-- arch/xtensa/include/asm/cmpxchg.h | 4 ++-- drivers/gpu/drm/i915/gt/intel_engine_cs.c | 2 +- .../gpu/drm/i915/gt/intel_engine_heartbeat.c | 4 ++-- .../drm/i915/gt/intel_execlists_submission.c | 4 ++-- drivers/gpu/drm/i915/gt/intel_ggtt.c | 4 ++-- drivers/gpu/drm/i915/gt/intel_gsc.c | 2 +- drivers/gpu/drm/i915/gt/intel_gt.c | 4 ++-- drivers/gpu/drm/i915/gt/intel_gt_pm.c | 2 +- drivers/gpu/drm/i915/gt/intel_lrc.c | 6 +++--- drivers/gpu/drm/i915/gt/intel_migrate.c | 2 +- drivers/gpu/drm/i915/gt/intel_rc6.c | 2 +- drivers/gpu/drm/i915/gt/intel_rps.c | 2 +- drivers/gpu/drm/i915/gt/selftest_context.c | 2 +- .../drm/i915/gt/selftest_ring_submission.c | 2 +- drivers/gpu/drm/i915/gt/selftest_timeline.c | 2 +- drivers/gpu/drm/i915/gt/uc/intel_gsc_uc.c | 2 +- drivers/gpu/drm/i915/gt/uc/intel_uc.c | 2 +- drivers/gpu/drm/i915/gt/uc/intel_uc_fw.c | 2 +- drivers/gpu/drm/i915/i915_utils.h | 1 + include/linux/non-atomic/xchg.h | 19 +++++++++++++++++++ 39 files changed, 84 insertions(+), 64 deletions(-) create mode 100644 include/linux/non-atomic/xchg.h