From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-10.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 90FD9C4360C for ; Sun, 29 Sep 2019 17:31:31 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 528FA21A4A for ; Sun, 29 Sep 2019 17:31:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1569778291; bh=I9IKwRqNjBya+//XLi4G7RG1Q/fT+hMum9Ow+lED6E8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=kCUwKQli21Ioa/fZNiYC5rn9V8oi/nq1u1Xejtdo/nB4cpWlbWpFGtKlr8LrA8c6O QReaDQuE7kuyVRjX8/ANQzdzIL02vc3AQJw1Wm4NhQMRtcWMFu1bL7xJzS5urJKXO6 sRmszK/3Hd9XJdOh/9PTVJZPU7Hdaucf4vYqsLNs= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729315AbfI2Rba (ORCPT ); Sun, 29 Sep 2019 13:31:30 -0400 Received: from mail.kernel.org ([198.145.29.99]:41868 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729238AbfI2Rb3 (ORCPT ); Sun, 29 Sep 2019 13:31:29 -0400 Received: from sasha-vm.mshome.net (c-73-47-72-35.hsd1.nh.comcast.net [73.47.72.35]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id A565621925; Sun, 29 Sep 2019 17:31:26 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1569778287; bh=I9IKwRqNjBya+//XLi4G7RG1Q/fT+hMum9Ow+lED6E8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=SJ4fcRiLNGGkobFeDE5720bh7FG0c+iUQTR3aHqlFPOKV9Jwo7aMdM8A8TcpTNym8 rRsHGf7GHfEeR+hRWohC4OsYAGTvBUMTUYwAB9RzPjR9sX/E7vvNeKpoDFmmuIM9JK UybwiE7+SzeWYcz9hdnRbWQ0rONOAo8HnkvekQ58= From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Peter Zijlstra , Andrea Parri , Paul Burton , Sasha Levin , linux-mips@vger.kernel.org Subject: [PATCH AUTOSEL 5.3 14/49] mips/atomic: Fix smp_mb__{before,after}_atomic() Date: Sun, 29 Sep 2019 13:30:14 -0400 Message-Id: <20190929173053.8400-14-sashal@kernel.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20190929173053.8400-1-sashal@kernel.org> References: <20190929173053.8400-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Peter Zijlstra [ Upstream commit 42344113ba7a1ed7b5654cd5270af0d5698d8521 ] Recent probing at the Linux Kernel Memory Model uncovered a 'surprise'. Strongly ordered architectures where the atomic RmW primitive implies full memory ordering and smp_mb__{before,after}_atomic() are a simple barrier() (such as MIPS without WEAK_REORDERING_BEYOND_LLSC) fail for: *x = 1; atomic_inc(u); smp_mb__after_atomic(); r0 = *y; Because, while the atomic_inc() implies memory order, it (surprisingly) does not provide a compiler barrier. This then allows the compiler to re-order like so: atomic_inc(u); *x = 1; smp_mb__after_atomic(); r0 = *y; Which the CPU is then allowed to re-order (under TSO rules) like: atomic_inc(u); r0 = *y; *x = 1; And this very much was not intended. Therefore strengthen the atomic RmW ops to include a compiler barrier. Reported-by: Andrea Parri Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Paul Burton Signed-off-by: Sasha Levin --- arch/mips/include/asm/atomic.h | 14 +++++------ arch/mips/include/asm/barrier.h | 12 ++++++++-- arch/mips/include/asm/bitops.h | 42 ++++++++++++++++++++------------- arch/mips/include/asm/cmpxchg.h | 6 ++--- 4 files changed, 45 insertions(+), 29 deletions(-) diff --git a/arch/mips/include/asm/atomic.h b/arch/mips/include/asm/atomic.h index 190f1b6151221..bb8658cc7f126 100644 --- a/arch/mips/include/asm/atomic.h +++ b/arch/mips/include/asm/atomic.h @@ -68,7 +68,7 @@ static __inline__ void atomic_##op(int i, atomic_t * v) \ "\t" __scbeqz " %0, 1b \n" \ " .set pop \n" \ : "=&r" (temp), "+" GCC_OFF_SMALL_ASM() (v->counter) \ - : "Ir" (i)); \ + : "Ir" (i) : __LLSC_CLOBBER); \ } else { \ unsigned long flags; \ \ @@ -98,7 +98,7 @@ static __inline__ int atomic_##op##_return_relaxed(int i, atomic_t * v) \ " .set pop \n" \ : "=&r" (result), "=&r" (temp), \ "+" GCC_OFF_SMALL_ASM() (v->counter) \ - : "Ir" (i)); \ + : "Ir" (i) : __LLSC_CLOBBER); \ } else { \ unsigned long flags; \ \ @@ -132,7 +132,7 @@ static __inline__ int atomic_fetch_##op##_relaxed(int i, atomic_t * v) \ " move %0, %1 \n" \ : "=&r" (result), "=&r" (temp), \ "+" GCC_OFF_SMALL_ASM() (v->counter) \ - : "Ir" (i)); \ + : "Ir" (i) : __LLSC_CLOBBER); \ } else { \ unsigned long flags; \ \ @@ -210,7 +210,7 @@ static __inline__ int atomic_sub_if_positive(int i, atomic_t * v) " .set pop \n" : "=&r" (result), "=&r" (temp), "+" GCC_OFF_SMALL_ASM() (v->counter) - : "Ir" (i)); + : "Ir" (i) : __LLSC_CLOBBER); } else { unsigned long flags; @@ -270,7 +270,7 @@ static __inline__ void atomic64_##op(s64 i, atomic64_t * v) \ "\t" __scbeqz " %0, 1b \n" \ " .set pop \n" \ : "=&r" (temp), "+" GCC_OFF_SMALL_ASM() (v->counter) \ - : "Ir" (i)); \ + : "Ir" (i) : __LLSC_CLOBBER); \ } else { \ unsigned long flags; \ \ @@ -300,7 +300,7 @@ static __inline__ s64 atomic64_##op##_return_relaxed(s64 i, atomic64_t * v) \ " .set pop \n" \ : "=&r" (result), "=&r" (temp), \ "+" GCC_OFF_SMALL_ASM() (v->counter) \ - : "Ir" (i)); \ + : "Ir" (i) : __LLSC_CLOBBER); \ } else { \ unsigned long flags; \ \ @@ -334,7 +334,7 @@ static __inline__ s64 atomic64_fetch_##op##_relaxed(s64 i, atomic64_t * v) \ " .set pop \n" \ : "=&r" (result), "=&r" (temp), \ "+" GCC_OFF_SMALL_ASM() (v->counter) \ - : "Ir" (i)); \ + : "Ir" (i) : __LLSC_CLOBBER); \ } else { \ unsigned long flags; \ \ diff --git a/arch/mips/include/asm/barrier.h b/arch/mips/include/asm/barrier.h index f9a6da96aae12..9228f73862205 100644 --- a/arch/mips/include/asm/barrier.h +++ b/arch/mips/include/asm/barrier.h @@ -211,14 +211,22 @@ #define __smp_wmb() barrier() #endif +/* + * When LL/SC does imply order, it must also be a compiler barrier to avoid the + * compiler from reordering where the CPU will not. When it does not imply + * order, the compiler is also free to reorder across the LL/SC loop and + * ordering will be done by smp_llsc_mb() and friends. + */ #if defined(CONFIG_WEAK_REORDERING_BEYOND_LLSC) && defined(CONFIG_SMP) #define __WEAK_LLSC_MB " sync \n" +#define smp_llsc_mb() __asm__ __volatile__(__WEAK_LLSC_MB : : :"memory") +#define __LLSC_CLOBBER #else #define __WEAK_LLSC_MB " \n" +#define smp_llsc_mb() do { } while (0) +#define __LLSC_CLOBBER "memory" #endif -#define smp_llsc_mb() __asm__ __volatile__(__WEAK_LLSC_MB : : :"memory") - #ifdef CONFIG_CPU_CAVIUM_OCTEON #define smp_mb__before_llsc() smp_wmb() #define __smp_mb__before_llsc() __smp_wmb() diff --git a/arch/mips/include/asm/bitops.h b/arch/mips/include/asm/bitops.h index 7bd35e5e2a9e4..985d6a02f9ea1 100644 --- a/arch/mips/include/asm/bitops.h +++ b/arch/mips/include/asm/bitops.h @@ -66,7 +66,8 @@ static inline void set_bit(unsigned long nr, volatile unsigned long *addr) " beqzl %0, 1b \n" " .set pop \n" : "=&r" (temp), "=" GCC_OFF_SMALL_ASM() (*m) - : "ir" (1UL << bit), GCC_OFF_SMALL_ASM() (*m)); + : "ir" (1UL << bit), GCC_OFF_SMALL_ASM() (*m) + : __LLSC_CLOBBER); #if defined(CONFIG_CPU_MIPSR2) || defined(CONFIG_CPU_MIPSR6) } else if (kernel_uses_llsc && __builtin_constant_p(bit)) { loongson_llsc_mb(); @@ -76,7 +77,8 @@ static inline void set_bit(unsigned long nr, volatile unsigned long *addr) " " __INS "%0, %3, %2, 1 \n" " " __SC "%0, %1 \n" : "=&r" (temp), "+" GCC_OFF_SMALL_ASM() (*m) - : "ir" (bit), "r" (~0)); + : "ir" (bit), "r" (~0) + : __LLSC_CLOBBER); } while (unlikely(!temp)); #endif /* CONFIG_CPU_MIPSR2 || CONFIG_CPU_MIPSR6 */ } else if (kernel_uses_llsc) { @@ -90,7 +92,8 @@ static inline void set_bit(unsigned long nr, volatile unsigned long *addr) " " __SC "%0, %1 \n" " .set pop \n" : "=&r" (temp), "+" GCC_OFF_SMALL_ASM() (*m) - : "ir" (1UL << bit)); + : "ir" (1UL << bit) + : __LLSC_CLOBBER); } while (unlikely(!temp)); } else __mips_set_bit(nr, addr); @@ -122,7 +125,8 @@ static inline void clear_bit(unsigned long nr, volatile unsigned long *addr) " beqzl %0, 1b \n" " .set pop \n" : "=&r" (temp), "+" GCC_OFF_SMALL_ASM() (*m) - : "ir" (~(1UL << bit))); + : "ir" (~(1UL << bit)) + : __LLSC_CLOBBER); #if defined(CONFIG_CPU_MIPSR2) || defined(CONFIG_CPU_MIPSR6) } else if (kernel_uses_llsc && __builtin_constant_p(bit)) { loongson_llsc_mb(); @@ -132,7 +136,8 @@ static inline void clear_bit(unsigned long nr, volatile unsigned long *addr) " " __INS "%0, $0, %2, 1 \n" " " __SC "%0, %1 \n" : "=&r" (temp), "+" GCC_OFF_SMALL_ASM() (*m) - : "ir" (bit)); + : "ir" (bit) + : __LLSC_CLOBBER); } while (unlikely(!temp)); #endif /* CONFIG_CPU_MIPSR2 || CONFIG_CPU_MIPSR6 */ } else if (kernel_uses_llsc) { @@ -146,7 +151,8 @@ static inline void clear_bit(unsigned long nr, volatile unsigned long *addr) " " __SC "%0, %1 \n" " .set pop \n" : "=&r" (temp), "+" GCC_OFF_SMALL_ASM() (*m) - : "ir" (~(1UL << bit))); + : "ir" (~(1UL << bit)) + : __LLSC_CLOBBER); } while (unlikely(!temp)); } else __mips_clear_bit(nr, addr); @@ -192,7 +198,8 @@ static inline void change_bit(unsigned long nr, volatile unsigned long *addr) " beqzl %0, 1b \n" " .set pop \n" : "=&r" (temp), "+" GCC_OFF_SMALL_ASM() (*m) - : "ir" (1UL << bit)); + : "ir" (1UL << bit) + : __LLSC_CLOBBER); } else if (kernel_uses_llsc) { unsigned long *m = ((unsigned long *) addr) + (nr >> SZLONG_LOG); unsigned long temp; @@ -207,7 +214,8 @@ static inline void change_bit(unsigned long nr, volatile unsigned long *addr) " " __SC "%0, %1 \n" " .set pop \n" : "=&r" (temp), "+" GCC_OFF_SMALL_ASM() (*m) - : "ir" (1UL << bit)); + : "ir" (1UL << bit) + : __LLSC_CLOBBER); } while (unlikely(!temp)); } else __mips_change_bit(nr, addr); @@ -244,7 +252,7 @@ static inline int test_and_set_bit(unsigned long nr, " .set pop \n" : "=&r" (temp), "+" GCC_OFF_SMALL_ASM() (*m), "=&r" (res) : "r" (1UL << bit) - : "memory"); + : __LLSC_CLOBBER); } else if (kernel_uses_llsc) { unsigned long *m = ((unsigned long *) addr) + (nr >> SZLONG_LOG); unsigned long temp; @@ -260,7 +268,7 @@ static inline int test_and_set_bit(unsigned long nr, " .set pop \n" : "=&r" (temp), "+" GCC_OFF_SMALL_ASM() (*m), "=&r" (res) : "r" (1UL << bit) - : "memory"); + : __LLSC_CLOBBER); } while (unlikely(!res)); res = temp & (1UL << bit); @@ -301,7 +309,7 @@ static inline int test_and_set_bit_lock(unsigned long nr, " .set pop \n" : "=&r" (temp), "+m" (*m), "=&r" (res) : "r" (1UL << bit) - : "memory"); + : __LLSC_CLOBBER); } else if (kernel_uses_llsc) { unsigned long *m = ((unsigned long *) addr) + (nr >> SZLONG_LOG); unsigned long temp; @@ -317,7 +325,7 @@ static inline int test_and_set_bit_lock(unsigned long nr, " .set pop \n" : "=&r" (temp), "+" GCC_OFF_SMALL_ASM() (*m), "=&r" (res) : "r" (1UL << bit) - : "memory"); + : __LLSC_CLOBBER); } while (unlikely(!res)); res = temp & (1UL << bit); @@ -360,7 +368,7 @@ static inline int test_and_clear_bit(unsigned long nr, " .set pop \n" : "=&r" (temp), "+" GCC_OFF_SMALL_ASM() (*m), "=&r" (res) : "r" (1UL << bit) - : "memory"); + : __LLSC_CLOBBER); #if defined(CONFIG_CPU_MIPSR2) || defined(CONFIG_CPU_MIPSR6) } else if (kernel_uses_llsc && __builtin_constant_p(nr)) { unsigned long *m = ((unsigned long *) addr) + (nr >> SZLONG_LOG); @@ -375,7 +383,7 @@ static inline int test_and_clear_bit(unsigned long nr, " " __SC "%0, %1 \n" : "=&r" (temp), "+" GCC_OFF_SMALL_ASM() (*m), "=&r" (res) : "ir" (bit) - : "memory"); + : __LLSC_CLOBBER); } while (unlikely(!temp)); #endif } else if (kernel_uses_llsc) { @@ -394,7 +402,7 @@ static inline int test_and_clear_bit(unsigned long nr, " .set pop \n" : "=&r" (temp), "+" GCC_OFF_SMALL_ASM() (*m), "=&r" (res) : "r" (1UL << bit) - : "memory"); + : __LLSC_CLOBBER); } while (unlikely(!res)); res = temp & (1UL << bit); @@ -437,7 +445,7 @@ static inline int test_and_change_bit(unsigned long nr, " .set pop \n" : "=&r" (temp), "+" GCC_OFF_SMALL_ASM() (*m), "=&r" (res) : "r" (1UL << bit) - : "memory"); + : __LLSC_CLOBBER); } else if (kernel_uses_llsc) { unsigned long *m = ((unsigned long *) addr) + (nr >> SZLONG_LOG); unsigned long temp; @@ -453,7 +461,7 @@ static inline int test_and_change_bit(unsigned long nr, " .set pop \n" : "=&r" (temp), "+" GCC_OFF_SMALL_ASM() (*m), "=&r" (res) : "r" (1UL << bit) - : "memory"); + : __LLSC_CLOBBER); } while (unlikely(!res)); res = temp & (1UL << bit); diff --git a/arch/mips/include/asm/cmpxchg.h b/arch/mips/include/asm/cmpxchg.h index f5994a332673b..c8a47d18f6288 100644 --- a/arch/mips/include/asm/cmpxchg.h +++ b/arch/mips/include/asm/cmpxchg.h @@ -61,7 +61,7 @@ extern unsigned long __xchg_called_with_bad_pointer(void) " .set pop \n" \ : "=&r" (__ret), "=" GCC_OFF_SMALL_ASM() (*m) \ : GCC_OFF_SMALL_ASM() (*m), "Jr" (val) \ - : "memory"); \ + : __LLSC_CLOBBER); \ } else { \ unsigned long __flags; \ \ @@ -134,8 +134,8 @@ static inline unsigned long __xchg(volatile void *ptr, unsigned long x, " .set pop \n" \ "2: \n" \ : "=&r" (__ret), "=" GCC_OFF_SMALL_ASM() (*m) \ - : GCC_OFF_SMALL_ASM() (*m), "Jr" (old), "Jr" (new) \ - : "memory"); \ + : GCC_OFF_SMALL_ASM() (*m), "Jr" (old), "Jr" (new) \ + : __LLSC_CLOBBER); \ loongson_llsc_mb(); \ } else { \ unsigned long __flags; \ -- 2.20.1