From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752554AbbJRLPY (ORCPT ); Sun, 18 Oct 2015 07:15:24 -0400 Received: from smtprelay2.synopsys.com ([198.182.60.111]:42142 "EHLO smtprelay.synopsys.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752114AbbJRLPV (ORCPT ); Sun, 18 Oct 2015 07:15:21 -0400 From: Alexey Brodkin To: Vineet Gupta CC: Aabid Rushdi , "linux-kernel@vger.kernel.org" , "peterz@infradead.org" , "linux-perf-users@vger.kernel.org" , "dvhart@linux.intel.com" , "dsahern@gmail.com" , "acme@redhat.com" Subject: Re: [RFC] perf: fix building for ARCv1 Thread-Topic: [RFC] perf: fix building for ARCv1 Thread-Index: AQHRCODGqUIZ06l560WdnGKbYbcPA55w+T8A Date: Sun, 18 Oct 2015 11:15:16 +0000 Message-ID: <1445166916.9672.10.camel@synopsys.com> References: <1445088959-3058-1-git-send-email-abrodkin@synopsys.com> In-Reply-To: Accept-Language: en-US, ru-RU Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-originating-ip: [10.225.15.89] Content-Type: text/plain; charset="utf-8" Content-ID: <9FBB3E5308CA9F44848E4D722EDE48F9@internal.synopsys.com> MIME-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: 8bit X-MIME-Autoconverted: from base64 to 8bit by mail.home.local id t9IBGAPk002552 Hi Vineet, Looks like this time atomics are a must. And that really sucks! See these commits that introduce usage of atomic_xxx() all around the perf and tools it uses: http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=f812d3045c2385ac16237e68b156859c4005526e http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=d3a7c489c7fd2463e3b2c3a2179c7be879dd9cb4 http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=7143849a5d6a5c623d81790d92f0033507c5b14f http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=59a51c1dc9fbb3fb4af928b852d7b35df83edd74 http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=e1ed3a5b87ed6759e16ec93f16aae83d2cc77ca2 and that's the one that introduced usage of the following generic gcc's atomics (__sync_add_and_fetch/__sync_sub_and_fetch): http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=da6d8567512df11e0473b710c07de87efde5709c So the best we may do is to implement detection of atomics in the toolchain and if there's no atomics hard stop with perf building. -Alexey On Sat, 2015-10-17 at 14:19 +0000, Vineet Gupta wrote: > On Saturday 17 October 2015 07:06 PM, Alexey Brodkin wrote: > > Perf uses atomic options and so it is required to have atomics enabled > > in toolchain. > > > > In case of ARC atomics are enabled by default for ARCv2 but disabled for > > ARCv1. Now we explicitly enable atomics for either ARC achitecture > > version so perf could be successfully built. > > > > Currently on attempt to build perf for ARCv1 you'll see tons of: > > ----------------->8----------------- > > undefined reference to `__sync_add_and_fetch_4' > > ----------------->8----------------- > > > > Still note if ARCv1 CPU is configured without LL/SC perf will crash on > > execution once "llock" instruction is attempted to be executed. > > Ok this fixes ARCompact - assuming it will have LL/SC. We do have old SoCs w/o > that support. > So what we are saying is that any arch (or a configuration thereof) which doesn't > support atomic r-m-w can't even build perf now - that sucks ! > > A better way would be to do feature test for __sync_xyz and make atomic_xxx > wrappers call __sync_xyz) vs. an empty stub. > So atleast such arches can build and do "some" perf work ! > > -Vineet > > > Cc: Vineet Gupta > > Cc: Peter Zijlstra > > Cc: Arnaldo Carvalho de Melo > > Signed-off-by: Alexey Brodkin > > --- > > tools/perf/config/Makefile | 5 +++++ > > 1 file changed, 5 insertions(+) > > > > diff --git a/tools/perf/config/Makefile b/tools/perf/config/Makefile > > index 38a0853..dc7c0a8 100644 > > --- a/tools/perf/config/Makefile > > +++ b/tools/perf/config/Makefile > > @@ -47,6 +47,11 @@ ifeq ($(ARCH),arm64) > > LIBUNWIND_LIBS = -lunwind -lunwind-aarch64 > > endif > > > > +# Additional ARCH settings for ARC > > +ifeq ($(ARCH),arc) > > + CFLAGS += -matomic > > +endif > > + > > ifeq ($(NO_PERF_REGS),0) > > $(call detected,CONFIG_PERF_REGS) > > endif > > {.n++%ݶw{.n+{G{ayʇڙ,jfhz_(階ݢj"mG?&~iOzv^m ?I