On Tue, Mar 21, 2017 at 10:20 PM, Arnd Bergmann <arnd@xxxxxxxx> wrote: > On Tue, Mar 21, 2017 at 7:06 PM, Dmitry Vyukov <dvyukov@xxxxxxxxxx> wrote: >> On Tue, Mar 21, 2017 at 11:41 AM, Mark Rutland <mark.rutland@xxxxxxx> wrote: >>> On Tue, Mar 21, 2017 at 12:25:06PM +0300, Andrey Ryabinin wrote: >> >> I don't mind changing READ_ONCE_NOCHECK to READ_ONCE. But I don't have >> strong preference either way. >> >> We could do: >> #define arch_atomic_read_is_already_instrumented 1 >> and then skip instrumentation in asm-generic if it's defined. But I >> don't think it's worth it. >> >> There is no functional difference, it's only an optimization (now >> somewhat questionable). As Andrey said, one can get a splash of >> reports anyway, and it's the first one that is important. We use KASAN >> with panic_on_warn=1 so we don't even see the rest. > > I'm getting couple of new stack size warnings that are all the result > of the _NOCHECK. > > /git/arm-soc/mm/page_alloc.c: In function 'show_free_areas': > /git/arm-soc/mm/page_alloc.c:4685:1: error: the frame size of 3368 > bytes is larger than 3072 bytes [-Werror=frame-larger-than=] > } > /git/arm-soc/lib/atomic64_test.c: In function 'test_atomic': > /git/arm-soc/lib/atomic64_test.c:148:1: error: the frame size of 6528 > bytes is larger than 3072 bytes [-Werror=frame-larger-than=] > } > ^ > /git/arm-soc/lib/atomic64_test.c: In function 'test_atomic64': > /git/arm-soc/lib/atomic64_test.c:243:1: error: the frame size of 7112 > bytes is larger than 3072 bytes [-Werror=frame-larger-than=] > > This is with my previous set of patches already applied, so > READ_ONCE should not cause problems. Reverting > the READ_ONCE_NOCHECK() in atomic_read() and atomic64_read() > back to READ_ONCE() > > I also get a build failure as a result of your patch, but this one is > not addressed by using READ_ONCE(): > > In file included from /git/arm-soc/arch/x86/include/asm/atomic.h:7:0, > from /git/arm-soc/include/linux/atomic.h:4, > from /git/arm-soc/arch/x86/include/asm/thread_info.h:53, > from /git/arm-soc/include/linux/thread_info.h:25, > from /git/arm-soc/arch/x86/include/asm/preempt.h:6, > from /git/arm-soc/include/linux/preempt.h:80, > from /git/arm-soc/include/linux/spinlock.h:50, > from /git/arm-soc/include/linux/mmzone.h:7, > from /git/arm-soc/include/linux/gfp.h:5, > from /git/arm-soc/include/linux/mm.h:9, > from /git/arm-soc/mm/slub.c:12: > /git/arm-soc/mm/slub.c: In function '__slab_free': > /git/arm-soc/arch/x86/include/asm/cmpxchg.h:174:2: error: 'asm' > operand has impossible constraints > asm volatile(pfx "cmpxchg%c4b %2; sete %0" \ > ^ > /git/arm-soc/arch/x86/include/asm/cmpxchg.h:183:2: note: in expansion > of macro '__cmpxchg_double' > __cmpxchg_double(LOCK_PREFIX, p1, p2, o1, o2, n1, n2) > ^~~~~~~~~~~~~~~~ > /git/arm-soc/include/asm-generic/atomic-instrumented.h:236:2: note: in > expansion of macro 'arch_cmpxchg_double' > arch_cmpxchg_double(____p1, (p2), (o1), (o2), (n1), (n2)); \ > ^~~~~~~~~~~~~~~~~~~ > /git/arm-soc/mm/slub.c:385:7: note: in expansion of macro 'cmpxchg_double' > if (cmpxchg_double(&page->freelist, &page->counters, > ^~~~~~~~~~~~~~ > /git/arm-soc/scripts/Makefile.build:308: recipe for target 'mm/slub.o' failed > > http://pastebin.com/raw/qXVpi9Ev has the defconfig file I used, and I get the > error with any gcc version I tried (4.9 through 7.0.1). Initially I've tested with my stock gcc 4.8.4 (Ubuntu 4.8.4-2ubuntu1~14.04.3) and amusingly it works. But I can reproduce the bug with 7.0.1. Filed https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80148 Will think about kernel fix. Thanks! -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
