Hi Mark, I love your patch! Perhaps something to improve: [auto build test WARNING on tip/perf/core] [also build test WARNING on v4.17-rc4 next-20180510] [if your patch is applied to the wrong git tree, please drop us a note to help improve the system] url: https://github.com/0day-ci/linux/commits/Mark-Rutland/perf-ring_buffer-ensure-atomicity-and-order-of-updates/20180511-070205 config: i386-randconfig-s0-201818 (attached as .config) compiler: gcc-6 (Debian 6.4.0-9) 6.4.0 20171026 reproduce: # save the attached .config to linux build tree make ARCH=i386 All warnings (new ones prefixed by >>): In file included from include/uapi/linux/swab.h:6:0, from include/linux/swab.h:5, from include/uapi/linux/byteorder/little_endian.h:13, from include/linux/byteorder/little_endian.h:5, from arch/x86/include/uapi/asm/byteorder.h:5, from include/uapi/linux/perf_event.h:20, from include/linux/perf_event.h:17, from kernel/events/ring_buffer.c:12: kernel/events/ring_buffer.c: In function 'perf_output_put_handle': include/linux/compiler.h:339:38: error: call to '__compiletime_assert_86' declared with attribute error: Need native word sized stores/loads for atomicity. _compiletime_assert(condition, msg, __compiletime_assert_, __LINE__) ^ include/linux/compiler.h:319:4: note: in definition of macro '__compiletime_assert' prefix ## suffix(); \ ^~~~~~ include/linux/compiler.h:339:2: note: in expansion of macro '_compiletime_assert' _compiletime_assert(condition, msg, __compiletime_assert_, __LINE__) ^~~~~~~~~~~~~~~~~~~ include/linux/compiler.h:342:2: note: in expansion of macro 'compiletime_assert' compiletime_assert(__native_word(t), \ ^~~~~~~~~~~~~~~~~~ >> arch/x86/include/asm/barrier.h:69:2: note: in expansion of macro 'compiletime_assert_atomic_type' compiletime_assert_atomic_type(*p); \ ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ >> include/asm-generic/barrier.h:157:33: note: in expansion of macro '__smp_store_release' #define smp_store_release(p, v) __smp_store_release(p, v) ^~~~~~~~~~~~~~~~~~~ kernel/events/ring_buffer.c:86:2: note: in expansion of macro 'smp_store_release' smp_store_release(&rb->user_page->data_head, head); /* B, matches C */ ^~~~~~~~~~~~~~~~~ kernel/events/ring_buffer.c: In function 'perf_aux_output_skip': include/linux/compiler.h:339:38: error: call to '__compiletime_assert_498' declared with attribute error: Need native word sized stores/loads for atomicity. _compiletime_assert(condition, msg, __compiletime_assert_, __LINE__) ^ include/linux/compiler.h:319:4: note: in definition of macro '__compiletime_assert' prefix ## suffix(); \ ^~~~~~ include/linux/compiler.h:339:2: note: in expansion of macro '_compiletime_assert' _compiletime_assert(condition, msg, __compiletime_assert_, __LINE__) ^~~~~~~~~~~~~~~~~~~ include/linux/compiler.h:342:2: note: in expansion of macro 'compiletime_assert' compiletime_assert(__native_word(t), \ ^~~~~~~~~~~~~~~~~~ >> arch/x86/include/asm/barrier.h:69:2: note: in expansion of macro 'compiletime_assert_atomic_type' compiletime_assert_atomic_type(*p); \ ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ >> include/asm-generic/barrier.h:157:33: note: in expansion of macro '__smp_store_release' #define smp_store_release(p, v) __smp_store_release(p, v) ^~~~~~~~~~~~~~~~~~~ kernel/events/ring_buffer.c:498:2: note: in expansion of macro 'smp_store_release' smp_store_release(&rb->user_page->aux_head, rb->aux_head); ^~~~~~~~~~~~~~~~~ kernel/events/ring_buffer.c: In function 'perf_aux_output_end': include/linux/compiler.h:339:38: error: call to '__compiletime_assert_466' declared with attribute error: Need native word sized stores/loads for atomicity. _compiletime_assert(condition, msg, __compiletime_assert_, __LINE__) ^ include/linux/compiler.h:319:4: note: in definition of macro '__compiletime_assert' prefix ## suffix(); \ ^~~~~~ include/linux/compiler.h:339:2: note: in expansion of macro '_compiletime_assert' _compiletime_assert(condition, msg, __compiletime_assert_, __LINE__) ^~~~~~~~~~~~~~~~~~~ include/linux/compiler.h:342:2: note: in expansion of macro 'compiletime_assert' compiletime_assert(__native_word(t), \ ^~~~~~~~~~~~~~~~~~ >> arch/x86/include/asm/barrier.h:69:2: note: in expansion of macro 'compiletime_assert_atomic_type' compiletime_assert_atomic_type(*p); \ ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ >> include/asm-generic/barrier.h:157:33: note: in expansion of macro '__smp_store_release' #define smp_store_release(p, v) __smp_store_release(p, v) ^~~~~~~~~~~~~~~~~~~ kernel/events/ring_buffer.c:466:2: note: in expansion of macro 'smp_store_release' smp_store_release(&rb->user_page->aux_head, rb->aux_head); ^~~~~~~~~~~~~~~~~ -- In file included from include/uapi/linux/swab.h:6:0, from include/linux/swab.h:5, from include/uapi/linux/byteorder/little_endian.h:13, from include/linux/byteorder/little_endian.h:5, from arch/x86/include/uapi/asm/byteorder.h:5, from include/uapi/linux/perf_event.h:20, from include/linux/perf_event.h:17, from kernel//events/ring_buffer.c:12: kernel//events/ring_buffer.c: In function 'perf_output_put_handle': include/linux/compiler.h:339:38: error: call to '__compiletime_assert_86' declared with attribute error: Need native word sized stores/loads for atomicity. _compiletime_assert(condition, msg, __compiletime_assert_, __LINE__) ^ include/linux/compiler.h:319:4: note: in definition of macro '__compiletime_assert' prefix ## suffix(); \ ^~~~~~ include/linux/compiler.h:339:2: note: in expansion of macro '_compiletime_assert' _compiletime_assert(condition, msg, __compiletime_assert_, __LINE__) ^~~~~~~~~~~~~~~~~~~ include/linux/compiler.h:342:2: note: in expansion of macro 'compiletime_assert' compiletime_assert(__native_word(t), \ ^~~~~~~~~~~~~~~~~~ >> arch/x86/include/asm/barrier.h:69:2: note: in expansion of macro 'compiletime_assert_atomic_type' compiletime_assert_atomic_type(*p); \ ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ >> include/asm-generic/barrier.h:157:33: note: in expansion of macro '__smp_store_release' #define smp_store_release(p, v) __smp_store_release(p, v) ^~~~~~~~~~~~~~~~~~~ kernel//events/ring_buffer.c:86:2: note: in expansion of macro 'smp_store_release' smp_store_release(&rb->user_page->data_head, head); /* B, matches C */ ^~~~~~~~~~~~~~~~~ kernel//events/ring_buffer.c: In function 'perf_aux_output_skip': include/linux/compiler.h:339:38: error: call to '__compiletime_assert_498' declared with attribute error: Need native word sized stores/loads for atomicity. _compiletime_assert(condition, msg, __compiletime_assert_, __LINE__) ^ include/linux/compiler.h:319:4: note: in definition of macro '__compiletime_assert' prefix ## suffix(); \ ^~~~~~ include/linux/compiler.h:339:2: note: in expansion of macro '_compiletime_assert' _compiletime_assert(condition, msg, __compiletime_assert_, __LINE__) ^~~~~~~~~~~~~~~~~~~ include/linux/compiler.h:342:2: note: in expansion of macro 'compiletime_assert' compiletime_assert(__native_word(t), \ ^~~~~~~~~~~~~~~~~~ >> arch/x86/include/asm/barrier.h:69:2: note: in expansion of macro 'compiletime_assert_atomic_type' compiletime_assert_atomic_type(*p); \ ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ >> include/asm-generic/barrier.h:157:33: note: in expansion of macro '__smp_store_release' #define smp_store_release(p, v) __smp_store_release(p, v) ^~~~~~~~~~~~~~~~~~~ kernel//events/ring_buffer.c:498:2: note: in expansion of macro 'smp_store_release' smp_store_release(&rb->user_page->aux_head, rb->aux_head); ^~~~~~~~~~~~~~~~~ kernel//events/ring_buffer.c: In function 'perf_aux_output_end': include/linux/compiler.h:339:38: error: call to '__compiletime_assert_466' declared with attribute error: Need native word sized stores/loads for atomicity. _compiletime_assert(condition, msg, __compiletime_assert_, __LINE__) ^ include/linux/compiler.h:319:4: note: in definition of macro '__compiletime_assert' prefix ## suffix(); \ ^~~~~~ include/linux/compiler.h:339:2: note: in expansion of macro '_compiletime_assert' _compiletime_assert(condition, msg, __compiletime_assert_, __LINE__) ^~~~~~~~~~~~~~~~~~~ include/linux/compiler.h:342:2: note: in expansion of macro 'compiletime_assert' compiletime_assert(__native_word(t), \ ^~~~~~~~~~~~~~~~~~ >> arch/x86/include/asm/barrier.h:69:2: note: in expansion of macro 'compiletime_assert_atomic_type' compiletime_assert_atomic_type(*p); \ ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ >> include/asm-generic/barrier.h:157:33: note: in expansion of macro '__smp_store_release' #define smp_store_release(p, v) __smp_store_release(p, v) ^~~~~~~~~~~~~~~~~~~ kernel//events/ring_buffer.c:466:2: note: in expansion of macro 'smp_store_release' smp_store_release(&rb->user_page->aux_head, rb->aux_head); ^~~~~~~~~~~~~~~~~ vim +/compiletime_assert_atomic_type +69 arch/x86/include/asm/barrier.h 47933ad4 Peter Zijlstra 2013-11-06 66 1638fb72 Michael S. Tsirkin 2015-12-27 67 #define __smp_store_release(p, v) \ 47933ad4 Peter Zijlstra 2013-11-06 68 do { \ 47933ad4 Peter Zijlstra 2013-11-06 @69 compiletime_assert_atomic_type(*p); \ 47933ad4 Peter Zijlstra 2013-11-06 70 barrier(); \ 76695af2 Andrey Konovalov 2015-08-02 71 WRITE_ONCE(*p, v); \ 47933ad4 Peter Zijlstra 2013-11-06 72 } while (0) 47933ad4 Peter Zijlstra 2013-11-06 73 :::::: The code at line 69 was first introduced by commit :::::: 47933ad41a86a4a9b50bed7c9b9bd2ba242aac63 arch: Introduce smp_load_acquire(), smp_store_release() :::::: TO: Peter Zijlstra :::::: CC: Ingo Molnar --- 0-DAY kernel test infrastructure Open Source Technology Center https://lists.01.org/pipermail/kbuild-all Intel Corporation