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Date: Fri, 19 Apr 2019 08:17:48 -0600
From: shuah <shuah@...nel.org>
To: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
Ingo Molnar <mingo@...nel.org>
Cc: Thomas Gleixner <tglx@...utronix.de>,
linux-kernel <linux-kernel@...r.kernel.org>,
linux-api <linux-api@...r.kernel.org>,
Peter Zijlstra <peterz@...radead.org>,
"Paul E . McKenney" <paulmck@...ux.vnet.ibm.com>,
Boqun Feng <boqun.feng@...il.com>,
Andy Lutomirski <luto@...capital.net>,
Dave Watson <davejwatson@...com>, Paul Turner <pjt@...gle.com>,
Andrew Morton <akpm@...ux-foundation.org>,
Russell King <linux@....linux.org.uk>,
Ingo Molnar <mingo@...hat.com>,
"H. Peter Anvin" <hpa@...or.com>, Andi Kleen <andi@...stfloor.org>,
Chris Lameter <cl@...ux.com>, Ben Maurer <bmaurer@...com>,
rostedt <rostedt@...dmis.org>,
Josh Triplett <josh@...htriplett.org>,
Linus Torvalds <torvalds@...ux-foundation.org>,
Catalin Marinas <catalin.marinas@....com>,
Will Deacon <will.deacon@....com>,
Michael Kerrisk <mtk.manpages@...il.com>,
Joel Fernandes <joelaf@...gle.com>,
linux-kselftest <linux-kselftest@...r.kernel.org>,
shuah <shuah@...nel.org>
Subject: Re: [PATCH for 5.1 3/3] rseq/selftests: Adapt number of threads to
the number of detected cpus
On 4/19/19 7:48 AM, Mathieu Desnoyers wrote:
> ----- On Apr 19, 2019, at 9:42 AM, Mathieu Desnoyers mathieu.desnoyers@...icios.com wrote:
>
>> ----- On Apr 19, 2019, at 8:55 AM, Mathieu Desnoyers
>> mathieu.desnoyers@...icios.com wrote:
>>
>>> ----- On Apr 19, 2019, at 8:41 AM, Mathieu Desnoyers
>>> mathieu.desnoyers@...icios.com wrote:
>>>
>>>> ----- On Apr 19, 2019, at 6:38 AM, Ingo Molnar mingo@...nel.org wrote:
>>>>
>>>>> * Mathieu Desnoyers <mathieu.desnoyers@...icios.com> wrote:
>>>>>
>>>>>> On smaller systems, running a test with 200 threads can take a long
>>>>>> time on machines with smaller number of CPUs.
>>>>>>
>>>>>> Detect the number of online cpus at test runtime, and multiply that
>>>>>> by 6 to have 6 rseq threads per cpu preempting each other.
>>>>>>
>>>>>> Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
>>>>>> Cc: Shuah Khan <shuah@...nel.org>
>>>>>> Cc: Thomas Gleixner <tglx@...utronix.de>
>>>>>> Cc: Joel Fernandes <joelaf@...gle.com>
>>>>>> Cc: Peter Zijlstra <peterz@...radead.org>
>>>>>> Cc: Catalin Marinas <catalin.marinas@....com>
>>>>>> Cc: Dave Watson <davejwatson@...com>
>>>>>> Cc: Will Deacon <will.deacon@....com>
>>>>>> Cc: Andi Kleen <andi@...stfloor.org>
>>>>>> Cc: linux-kselftest@...r.kernel.org
>>>>>> Cc: "H . Peter Anvin" <hpa@...or.com>
>>>>>> Cc: Chris Lameter <cl@...ux.com>
>>>>>> Cc: Russell King <linux@....linux.org.uk>
>>>>>> Cc: Michael Kerrisk <mtk.manpages@...il.com>
>>>>>> Cc: "Paul E . McKenney" <paulmck@...ux.vnet.ibm.com>
>>>>>> Cc: Paul Turner <pjt@...gle.com>
>>>>>> Cc: Boqun Feng <boqun.feng@...il.com>
>>>>>> Cc: Josh Triplett <josh@...htriplett.org>
>>>>>> Cc: Steven Rostedt <rostedt@...dmis.org>
>>>>>> Cc: Ben Maurer <bmaurer@...com>
>>>>>> Cc: Andy Lutomirski <luto@...capital.net>
>>>>>> Cc: Andrew Morton <akpm@...ux-foundation.org>
>>>>>> Cc: Linus Torvalds <torvalds@...ux-foundation.org>
>>>>>> ---
>>>>>> tools/testing/selftests/rseq/run_param_test.sh | 7 +++++--
>>>>>> 1 file changed, 5 insertions(+), 2 deletions(-)
>>>>>>
>>>>>> diff --git a/tools/testing/selftests/rseq/run_param_test.sh
>>>>>> b/tools/testing/selftests/rseq/run_param_test.sh
>>>>>> index 3acd6d75ff9f..e426304fd4a0 100755
>>>>>> --- a/tools/testing/selftests/rseq/run_param_test.sh
>>>>>> +++ b/tools/testing/selftests/rseq/run_param_test.sh
>>>>>> @@ -1,6 +1,8 @@
>>>>>> #!/bin/bash
>>>>>> # SPDX-License-Identifier: GPL-2.0+ or MIT
>>>>>>
>>>>>> +NR_CPUS=`grep '^processor' /proc/cpuinfo | wc -l`
>>>>>> +
>>>>>> EXTRA_ARGS=${@}
>>>>>>
>>>>>> OLDIFS="$IFS"
>>>>>> @@ -28,15 +30,16 @@ IFS="$OLDIFS"
>>>>>>
>>>>>> REPS=1000
>>>>>> SLOW_REPS=100
>>>>>> +NR_THREADS=$((6*${NR_CPUS}))
>>>>>>
>>>>>> function do_tests()
>>>>>> {
>>>>>> local i=0
>>>>>> while [ "$i" -lt "${#TEST_LIST[@]}" ]; do
>>>>>> echo "Running test ${TEST_NAME[$i]}"
>>>>>> - ./param_test ${TEST_LIST[$i]} -r ${REPS} ${@} ${EXTRA_ARGS} || exit 1
>>>>>> + ./param_test ${TEST_LIST[$i]} -r ${REPS} -t ${NR_THREADS} ${@} ${EXTRA_ARGS}
>>>>>> || exit 1
>>>>>> echo "Running compare-twice test ${TEST_NAME[$i]}"
>>>>>> - ./param_test_compare_twice ${TEST_LIST[$i]} -r ${REPS} ${@} ${EXTRA_ARGS} ||
>>>>>> exit 1
>>>>>> + ./param_test_compare_twice ${TEST_LIST[$i]} -r ${REPS} -t ${NR_THREADS} ${@}
>>>>>> ${EXTRA_ARGS} || exit 1
>>>>>> let "i++"
>>>>>> done
>>>>>> }
>>>>>
>>>>> BTW., when trying to build the rseq self-tests I get this build failure:
>>>>>
>>>>> dagon:~/tip/tools/testing/selftests/rseq> make
>>>>> gcc -O2 -Wall -g -I./ -I../../../../usr/include/ -L./ -Wl,-rpath=./ -shared
>>>>> -fPIC rseq.c -lpthread -o
>>>>> /home/mingo/tip/tools/testing/selftests/rseq/librseq.so
>>>>> gcc -O2 -Wall -g -I./ -I../../../../usr/include/ -L./ -Wl,-rpath=./ basic_test.c
>>>>> -lpthread -lrseq -o /home/mingo/tip/tools/testing/selftests/rseq/basic_test
>>>>> gcc -O2 -Wall -g -I./ -I../../../../usr/include/ -L./ -Wl,-rpath=./
>>>>> basic_percpu_ops_test.c -lpthread -lrseq -o
>>>>> /home/mingo/tip/tools/testing/selftests/rseq/basic_percpu_ops_test
>>>>> /usr/bin/ld: /tmp/ccuHTWnZ.o: in function `rseq_cmpeqv_storev':
>>>>> /home/mingo/tip/tools/testing/selftests/rseq/./rseq-x86.h:84: undefined
>>>>> reference to `.L8'
>>>>> /usr/bin/ld: /home/mingo/tip/tools/testing/selftests/rseq/./rseq-x86.h:84:
>>>>> undefined reference to `.L49'
>>>>> /usr/bin/ld: /tmp/ccuHTWnZ.o: in function `rseq_cmpnev_storeoffp_load':
>>>>> /home/mingo/tip/tools/testing/selftests/rseq/./rseq-x86.h:141: undefined
>>>>> reference to `.L57'
>>>>> /usr/bin/ld: /tmp/ccuHTWnZ.o:(__rseq_failure+0x8): undefined reference to `.L8'
>>>>> /usr/bin/ld: /tmp/ccuHTWnZ.o:(__rseq_failure+0x14): undefined reference to
>>>>> `.L49'
>>>>> /usr/bin/ld: /tmp/ccuHTWnZ.o:(__rseq_failure+0x20): undefined reference to
>>>>> `.L55'
>>>>> collect2: error: ld returned 1 exit status
>>>>> make: *** [Makefile:22:
>>>>> /home/mingo/tip/tools/testing/selftests/rseq/basic_percpu_ops_test] Error 1
>>>>>
>>>>> Is this a known problem, or do I miss something from my build environment
>>>>> perhaps? Vanilla 64-bit Ubuntu 18.10 (Cosmic).
>>>>
>>>> It works fine with gcc-7 (gcc version 7.3.0 (Ubuntu 7.3.0-16ubuntu3))
>>>> but indeed I get the same failure with gcc-8 (gcc version 8.0.1 20180414
>>>> (experimental) [trunk revision 259383] (Ubuntu 8-20180414-1ubuntu2)).
>>>>
>>>> Thanks for reporting! I will investigate.
>>>
>>> It looks like gcc-8 optimize away the target of asm goto labels when
>>> there are more than one of them on x86-64. I'll try to come up with
>>> a simpler reproducer.
>>
>> It appears to be related to gcc-8 mishandling combination of
>> asm goto and thread-local storage input operands on x86-64.
>> Here is a simple reproducer:
>>
>> __thread int var;
>>
>> static int fct(void)
>> {
>> asm goto ( "jmp %l[testlabel]\n\t"
>> : : [var] "m" (var) : : testlabel);
>> return 0;
>> testlabel:
>
> FWIW, if I add an empty
>
> asm volatile ("");
>
> here after the label, gcc-8 -O2 builds "something" which is
> a bogus assembler (an endless loop) :
>
> main:
> .LFB24:
> .cfi_startproc
> .L2:
> subq $8, %rsp
> .cfi_def_cfa_offset 16
> #APP
> # 6 "test-asm-goto.c" 1
> jmp .L2
>
> # 0 "" 2
> #NO_APP
> movl %fs:var@...ff, %edx
> leaq .LC0(%rip), %rsi
> movl $1, %edi
> xorl %eax, %eax
> call __printf_chk@PLT
> xorl %eax, %eax
> addq $8, %rsp
> .cfi_def_cfa_offset 8
> ret
> .cfi_endproc
>
> Thoughts ?
>
Didn't see problems when I tested it before applying it to
linux-kselftest next.
I have gcc version 7.3.0 (Ubuntu 7.3.0-27ubuntu1~18.04)
thanks,
-- Shuah
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