From: Michal Hocko <mhocko@kernel.org>
To: Ingo Molnar <mingo@kernel.org>
Cc: LKML <linux-kernel@vger.kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@redhat.com>,
Thomas Gleixner <tglx@linutronix.de>,
"H. Peter Anvin" <hpa@zytor.com>,
"David S. Miller" <davem@davemloft.net>,
Tony Luck <tony.luck@intel.com>,
Andrew Morton <akpm@linux-foundation.org>,
Chris Zankel <chris@zankel.net>,
Max Filippov <jcmvbkbc@gmail.com>,
x86@kernel.org, linux-alpha@vger.kernel.org,
linux-ia64@vger.kernel.org, linux-s390@vger.kernel.org,
linux-sh@vger.kernel.org, sparclinux@vger.kernel.org,
linux-xtensa@linux-xtensa.org, linux-arch@vger.kernel.org,
Josh Poimboeuf <jpoimboe@redhat.com>
Subject: Re: [PATCH 10/11] x86, rwsem: provide __down_write_killable
Date: Sun, 17 Apr 2016 12:59:21 -0400 [thread overview]
Message-ID: <20160417165920.GA9051@dhcp22.suse.cz> (raw)
In-Reply-To: <20160413124943.GH14351@dhcp22.suse.cz>
On Wed 13-04-16 14:49:43, Michal Hocko wrote:
> On Wed 13-04-16 12:27:31, Ingo Molnar wrote:
> >
> > * Ingo Molnar <mingo@kernel.org> wrote:
> >
> > > I'm testing your patches today, if they are otherwise OK [...]
> >
> > got this build failure:
> >
> > ./arch/x86/include/asm/rwsem.h:106:2: error: ‘asm’ operand has impossible constraints
>
> Hmm, I have no idea why 64b didn't have problem with the asm but 32b
> complains. Anyway, the following makes both happy. I have checked the
> generated code for 64b and it hasn't changed after the patch. 32b also
> seems to be generating a proper code. My gcc asm()-foo is rather weak so
> I would feel better if somebody double checked after me.
Peter, Ingo, does the patch makes sense to you?
Thanks!
> ---
> From d23f4e6994670bf2c5d864f2190f21022b4499b2 Mon Sep 17 00:00:00 2001
> From: Michal Hocko <mhocko@suse.com>
> Date: Wed, 13 Apr 2016 14:21:25 +0200
> Subject: [PATCH] x86: __down_read_trylock fix 32b build failure
> MIME-Version: 1.0
> Content-Type: text/plain; charset=UTF-8
> Content-Transfer-Encoding: 8bit
>
> Ingo has noticed the following compilation error with CONFIG_X86_32=y
> ./arch/x86/include/asm/rwsem.h:106:2: error: ‘asm’ operand has impossible constraints
>
> The reason seems to be that 32b doesn't like ret being input and output
> argument sharing the same register with sem which is only the input. Fix
> this by making ret output only and use %3 (aka sem) for xadd.
>
> ret initialization is not needed now because this is done implicitly
> by the asm even for the fast path as both sem and ret share the same
> register.
>
> Reported-by: Ingo Molnar <mingo@kernel.org>
> Signed-off-by: Michal Hocko <mhocko@suse.com>
> ---
> arch/x86/include/asm/rwsem.h | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/arch/x86/include/asm/rwsem.h b/arch/x86/include/asm/rwsem.h
> index d759c5f70f49..453744c1d347 100644
> --- a/arch/x86/include/asm/rwsem.h
> +++ b/arch/x86/include/asm/rwsem.h
> @@ -102,9 +102,9 @@ static inline int __down_read_trylock(struct rw_semaphore *sem)
> #define ____down_write(sem, slow_path) \
> ({ \
> long tmp; \
> - struct rw_semaphore* ret = sem; \
> + struct rw_semaphore* ret; \
> asm volatile("# beginning down_write\n\t" \
> - LOCK_PREFIX " xadd %1,(%2)\n\t" \
> + LOCK_PREFIX " xadd %1,(%3)\n\t" \
> /* adds 0xffff0001, returns the old value */ \
> " test " __ASM_SEL(%w1,%k1) "," __ASM_SEL(%w1,%k1) "\n\t" \
> /* was the active mask 0 before? */\
> @@ -112,7 +112,7 @@ static inline int __down_read_trylock(struct rw_semaphore *sem)
> " call " slow_path "\n" \
> "1:\n" \
> "# ending down_write" \
> - : "+m" (sem->count), "=d" (tmp), "+a" (ret) \
> + : "+m" (sem->count), "=d" (tmp), "=a" (ret) \
> : "a" (sem), "1" (RWSEM_ACTIVE_WRITE_BIAS) \
> : "memory", "cc"); \
> ret; \
> --
> 2.8.0.rc3
>
> --
> Michal Hocko
> SUSE Labs
--
Michal Hocko
SUSE Labs
next prev parent reply other threads:[~2016-04-17 16:59 UTC|newest]
Thread overview: 52+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-04-07 15:12 [PATCH 0/11] introduce down_write_killable for rw_semaphore v3 Michal Hocko
2016-04-07 15:12 ` [PATCH 01/11] locking, rwsem: get rid of __down_write_nested Michal Hocko
2016-04-13 11:32 ` [tip:locking/rwsem] locking/rwsem: Get rid of __down_write_nested() tip-bot for Michal Hocko
2016-04-07 15:12 ` [PATCH 02/11] locking, rwsem: drop explicit memory barriers Michal Hocko
2016-04-13 11:32 ` [tip:locking/rwsem] locking/rwsem: Drop " tip-bot for Michal Hocko
2016-04-07 15:12 ` [PATCH 03/11] xtensa, rwsem: drop superfluous arch specific implementation Michal Hocko
2016-04-13 11:33 ` [tip:locking/rwsem] locking/rwsem, xtensa: Drop " tip-bot for Michal Hocko
2016-04-07 15:12 ` [PATCH 04/11] sh, rwsem: drop " Michal Hocko
2016-04-13 11:33 ` [tip:locking/rwsem] locking/rwsem, sh: Drop " tip-bot for Michal Hocko
2016-04-07 15:12 ` [PATCH 05/11] sparc, rwsem: drop " Michal Hocko
2016-04-13 11:33 ` [tip:locking/rwsem] locking/rwsem, sparc: Drop " tip-bot for Michal Hocko
2016-04-07 15:12 ` [PATCH 06/11] locking, rwsem: introduce basis for down_write_killable Michal Hocko
2016-04-13 11:34 ` [tip:locking/rwsem] locking/rwsem: Introduce basis for down_write_killable() tip-bot for Michal Hocko
2016-04-07 15:12 ` [PATCH 07/11] alpha, rwsem: provide __down_write_killable Michal Hocko
2016-04-22 9:42 ` [tip:locking/rwsem] locking/rwsem, alpha: Provide __down_write_killable() tip-bot for Michal Hocko
2016-04-07 15:12 ` [PATCH 08/11] ia64, rwsem: provide __down_write_killable Michal Hocko
2016-04-07 17:28 ` Sergei Shtylyov
2016-04-08 6:22 ` Michal Hocko
2016-04-22 9:43 ` [tip:locking/rwsem] locking/rwsem, ia64: Provide __down_write_killable() tip-bot for Michal Hocko
2016-04-07 15:12 ` [PATCH 09/11] s390, rwsem: provide __down_write_killable Michal Hocko
2016-04-22 9:43 ` [tip:locking/rwsem] locking/rwsem, s390: Provide __down_write_killable() tip-bot for Michal Hocko
2016-04-07 15:12 ` [PATCH 10/11] x86, rwsem: provide __down_write_killable Michal Hocko
2016-04-13 9:08 ` Ingo Molnar
2016-04-13 9:16 ` Michal Hocko
2016-04-13 9:19 ` Ingo Molnar
2016-04-13 10:27 ` Ingo Molnar
2016-04-13 12:49 ` Michal Hocko
2016-04-17 16:59 ` Michal Hocko [this message]
2016-04-20 13:40 ` Peter Zijlstra
2016-04-20 18:04 ` H. Peter Anvin
2016-04-20 20:45 ` Borislav Petkov
2016-04-20 20:58 ` Michal Hocko
2016-04-20 21:06 ` H. Peter Anvin
2016-04-20 21:36 ` Borislav Petkov
2016-04-20 22:29 ` H. Peter Anvin
2016-04-21 11:35 ` Borislav Petkov
2016-04-21 13:09 ` Michal Hocko
2016-04-21 13:21 ` Borislav Petkov
2016-04-27 12:02 ` [PATCH] x86/locking/rwsem: Cleanup ____down_write() Borislav Petkov
2016-04-28 10:27 ` [tip:locking/rwsem] locking/rwsem, x86: Clean up ____down_write() tip-bot for Borislav Petkov
2016-04-22 6:53 ` [PATCH 10/11] x86, rwsem: provide __down_write_killable Ingo Molnar
2016-04-13 9:57 ` [PATCH] x86: add frame annotation for call_rwsem_down_write_failed_killable Michal Hocko
2016-04-22 9:44 ` [tip:locking/rwsem] locking/rwsem, x86: Add frame annotation for call_rwsem_down_write_failed_killable() tip-bot for Michal Hocko
2016-04-22 9:43 ` [tip:locking/rwsem] locking/rwsem, x86: Provide __down_write_killable() tip-bot for Michal Hocko
2016-04-07 15:12 ` [PATCH 11/11] locking, rwsem: provide down_write_killable Michal Hocko
2016-04-22 9:44 ` [tip:locking/rwsem] locking/rwsem: Provide down_write_killable() tip-bot for Michal Hocko
2016-04-12 9:37 ` [PATCH 0/11] introduce down_write_killable for rw_semaphore v3 Michal Hocko
2016-04-12 15:40 ` Peter Zijlstra
2016-04-12 18:01 ` Michal Hocko
-- strict thread matches above, loose matches on Subject: below --
2016-04-01 11:04 [PATCH 0/11] introduce down_write_killable for rw_semaphore v2 Michal Hocko
2016-04-01 11:04 ` [PATCH 10/11] x86, rwsem: provide __down_write_killable Michal Hocko
2016-04-06 18:31 ` Peter Zijlstra
2016-02-29 12:58 [PATCH 0/11] introduce down_write_killable for rw_semaphore Michal Hocko
2016-02-29 12:58 ` [PATCH 10/11] x86, rwsem: provide __down_write_killable Michal Hocko
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