Re: [PATCH] perf/ring_buffer: ensure atomicity and order of updates

From: kbuild test robot
Date: Thu May 10 2018 - 21:20:35 EST

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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 <peterz@xxxxxxxxxxxxx>
:::::: CC: Ingo Molnar <mingo@xxxxxxxxxx>

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