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SubjectRe: [PATCH for 5.1 3/3] rseq/selftests: Adapt number of threads to the number of detected cpus
----- On Apr 19, 2019, at 8:41 AM, Mathieu Desnoyers mathieu.desnoyers@efficios.com wrote:

> ----- On Apr 19, 2019, at 6:38 AM, Ingo Molnar mingo@kernel.org wrote:
>
>> * Mathieu Desnoyers <mathieu.desnoyers@efficios.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@efficios.com>
>>> Cc: Shuah Khan <shuah@kernel.org>
>>> Cc: Thomas Gleixner <tglx@linutronix.de>
>>> Cc: Joel Fernandes <joelaf@google.com>
>>> Cc: Peter Zijlstra <peterz@infradead.org>
>>> Cc: Catalin Marinas <catalin.marinas@arm.com>
>>> Cc: Dave Watson <davejwatson@fb.com>
>>> Cc: Will Deacon <will.deacon@arm.com>
>>> Cc: Andi Kleen <andi@firstfloor.org>
>>> Cc: linux-kselftest@vger.kernel.org
>>> Cc: "H . Peter Anvin" <hpa@zytor.com>
>>> Cc: Chris Lameter <cl@linux.com>
>>> Cc: Russell King <linux@arm.linux.org.uk>
>>> Cc: Michael Kerrisk <mtk.manpages@gmail.com>
>>> Cc: "Paul E . McKenney" <paulmck@linux.vnet.ibm.com>
>>> Cc: Paul Turner <pjt@google.com>
>>> Cc: Boqun Feng <boqun.feng@gmail.com>
>>> Cc: Josh Triplett <josh@joshtriplett.org>
>>> Cc: Steven Rostedt <rostedt@goodmis.org>
>>> Cc: Ben Maurer <bmaurer@fb.com>
>>> Cc: Andy Lutomirski <luto@amacapital.net>
>>> Cc: Andrew Morton <akpm@linux-foundation.org>
>>> Cc: Linus Torvalds <torvalds@linux-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.

Thanks,

Mathieu


--
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com

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