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@efficios.com wrote:

quoted

----- On Apr 19, 2019, at 8:55 AM, Mathieu Desnoyers
mathieu.desnoyers@efficios.com wrote:

quoted

----- On Apr 19, 2019, at 8:41 AM, Mathieu Desnoyers
mathieu.desnoyers@efficios.com wrote:

quoted

----- On Apr 19, 2019, at 6:38 AM, Ingo Molnar mingo@kernel.org wrote:

quoted

* Mathieu Desnoyers [off-list ref] wrote:

quoted

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 <redacted>
Cc: Joel Fernandes <redacted>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Dave Watson <redacted>
Cc: Will Deacon <redacted>
Cc: Andi Kleen <redacted>
Cc: linux-kselftest@vger.kernel.org
Cc: "H . Peter Anvin" <hpa@zytor.com>
Cc: Chris Lameter <redacted>
Cc: Russell King <redacted>
Cc: Michael Kerrisk <redacted>
Cc: "Paul E . McKenney" <redacted>
Cc: Paul Turner <redacted>
Cc: Boqun Feng <redacted>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Ben Maurer <redacted>
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.

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@tpoff, %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