Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933834AbbDVDA2 (ORCPT ); Tue, 21 Apr 2015 23:00:28 -0400 Received: from mail-oi0-f42.google.com ([209.85.218.42]:35985 "EHLO mail-oi0-f42.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754267AbbDVDAZ (ORCPT ); Tue, 21 Apr 2015 23:00:25 -0400 MIME-Version: 1.0 In-Reply-To: <20150421154108.GA20223@roeck-us.net> References: <20150420194028.GA10814@roeck-us.net> <20150420210933.GB31618@fuloong-minipc.musicnaut.iki.fi> <87fv7up15k.fsf@rustcorp.com.au> <20150421154108.GA20223@roeck-us.net> From: Florian Fainelli Date: Tue, 21 Apr 2015 19:59:44 -0700 Message-ID: Subject: Re: mips build failures due to commit 8dd928915a73 (mips: fix up obsolete cpu function usage) To: Guenter Roeck Cc: Rusty Russell , Aaro Koskinen , "linux-kernel@vger.kernel.org" , Ralf Baechle , Linux-MIPS Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 5196 Lines: 136 2015-04-21 8:41 GMT-07:00 Guenter Roeck : > On Tue, Apr 21, 2015 at 01:45:35PM +0930, Rusty Russell wrote: >> Aaro Koskinen writes: >> > Hi, >> > >> > On Mon, Apr 20, 2015 at 12:40:28PM -0700, Guenter Roeck wrote: >> >> the upstream kernel fails to build mips:nlm_xlp_defconfig, >> >> mips:nlm_xlp_defconfig, mips:cavium_octeon_defconfig, and possibly >> >> other targets, with errors such as >> >> >> >> arch/mips/kernel/smp.c:211:2: error: >> >> passing argument 2 of 'cpumask_set_cpu' discards 'volatile' qualifier >> >> from pointer target type >> >> arch/mips/kernel/process.c:52:2: error: >> >> passing argument 2 of 'cpumask_test_cpu' discards 'volatile' qualifier >> >> from pointer target type >> >> arch/mips/cavium-octeon/smp.c:242:2: error: >> >> passing argument 2 of 'cpumask_clear_cpu' discards 'volatile' qualifier >> >> from pointer target type >> >> >> >> The problem was introduced with commit 8dd928915a73 (" mips: fix up >> >> obsolete cpu function usage"). I would send a patch to fix it, but I >> >> am not sure if removing 'volatile' from the variable declaration(s) >> >> would be a good idea. >> > >> > I think removing volatile from cpu_callin_map declaration should be OK, >> > since test_cpu (only reader) uses test_bit which takes care of it: >> > >> > static inline int test_bit(int nr, const volatile unsigned long *addr) >> >> No, that got replaced too, with cpumask_test_cpu AFAICT. >> >> You can open-code it, like so: >> >> test_bit(0, cpumask_bits(cpu_callin_map)); >> >> But you probably want to put a barrier in that loop instead of relying >> on volatile. >> > The following might do it. Note that I can not really test it since I don't have > a real mips system, and qemu gets rcu hangs if I enable more than one CPU (I see > that with older kernels as well, so it is not a new problem). Someone will have > to test the patch on a real multi-core system. Would be nice to get this merged ASAP as a build failure is not great. See below for the tested tag, thanks for the fix! > > Guenter > > --- > From 94026cc98a6b7b3567780a5443674c71202e2497 Mon Sep 17 00:00:00 2001 > From: Guenter Roeck > Date: Tue, 21 Apr 2015 08:31:01 -0700 > Subject: [PATCH] mips: Fix SMP builds > > Mips SMP builds fail with error messages similar to the following. > > arch/mips/kernel/smp.c:211:2: error: > passing argument 2 of 'cpumask_set_cpu' discards 'volatile' > qualifier from pointer target type > arch/mips/kernel/process.c:52:2: error: > passing argument 2 of 'cpumask_test_cpu' discards 'volatile' > qualifier from pointer target type > arch/mips/cavium-octeon/smp.c:242:2: error: > passing argument 2 of 'cpumask_clear_cpu' discards 'volatile' > qualifier from pointer target type > > cpu_callin_map is declared as volatile variable, but passed to various > functions with non-volatile arguments. Make it non-volatile and add a > memory barrier at the one location where volatile might be needed. > > Fixes: 8dd928915a73 ("mips: fix up obsolete cpu function usage") > Cc: Rusty Russell > Signed-off-by: Guenter Roeck On Netlogic XLP-FVP (8 cores): Tested-by: Florian Fainelli > --- > arch/mips/include/asm/smp.h | 2 +- > arch/mips/kernel/smp.c | 6 ++++-- > 2 files changed, 5 insertions(+), 3 deletions(-) > > diff --git a/arch/mips/include/asm/smp.h b/arch/mips/include/asm/smp.h > index bb02fac9b4fa..2b25d1ba1ea0 100644 > --- a/arch/mips/include/asm/smp.h > +++ b/arch/mips/include/asm/smp.h > @@ -45,7 +45,7 @@ extern int __cpu_logical_map[NR_CPUS]; > #define SMP_DUMP 0x8 > #define SMP_ASK_C0COUNT 0x10 > > -extern volatile cpumask_t cpu_callin_map; > +extern cpumask_t cpu_callin_map; > > /* Mask of CPUs which are currently definitely operating coherently */ > extern cpumask_t cpu_coherent_mask; > diff --git a/arch/mips/kernel/smp.c b/arch/mips/kernel/smp.c > index 193ace7955fb..158191394770 100644 > --- a/arch/mips/kernel/smp.c > +++ b/arch/mips/kernel/smp.c > @@ -43,7 +43,7 @@ > #include > #include > > -volatile cpumask_t cpu_callin_map; /* Bitmask of started secondaries */ > +cpumask_t cpu_callin_map; /* Bitmask of started secondaries */ > > int __cpu_number_map[NR_CPUS]; /* Map physical to logical */ > EXPORT_SYMBOL(__cpu_number_map); > @@ -218,8 +218,10 @@ int __cpu_up(unsigned int cpu, struct task_struct *tidle) > /* > * Trust is futile. We should really have timeouts ... > */ > - while (!cpumask_test_cpu(cpu, &cpu_callin_map)) > + while (!cpumask_test_cpu(cpu, &cpu_callin_map)) { > udelay(100); > + mb(); > + } > > synchronise_count_master(cpu); > return 0; > -- > 2.1.0 > -- Florian -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/