----- On Apr 19, 2019, at 10:17 AM, shuah shuah@kernel.org wrote:
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:
----- On Apr 19, 2019, at 8:55 AM, Mathieu Desnoyers mathieu.desnoyers@efficios.com wrote:
----- 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.
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)
It really appears to be an optimization bug in gcc-8. Considering that bogus compilers are released in the wild, we can hardly justify using the compiler feature that triggers the bogus behavior, even if it gets fixed in the future.
I've prepared a patch that changes the way the __rseq_abi fields are passed to the inline asm. I pass the address of the __rseq_abi TLS as a register input operand rather than each individual field as "m" operand.
I will submit it in a separate thread.
By the way, it affects both x86-32 (building with gcc-8 -m32) and x86-64.
Thanks,
Mathieu