Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756555AbbHNSbz (ORCPT ); Fri, 14 Aug 2015 14:31:55 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:50993 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755354AbbHNRmz (ORCPT ); Fri, 14 Aug 2015 13:42:55 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, David Daney , linux-mips@linux-mips.org, Ralf Baechle Subject: [PATCH 4.1 10/84] MIPS: Make set_pte() SMP safe. Date: Fri, 14 Aug 2015 10:41:38 -0700 Message-Id: <20150814174210.523622530@linuxfoundation.org> X-Mailer: git-send-email 2.5.0 In-Reply-To: <20150814174210.214822912@linuxfoundation.org> References: <20150814174210.214822912@linuxfoundation.org> User-Agent: quilt/0.64 MIME-Version: 1.0 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: 2488 Lines: 83 4.1-stable review patch. If anyone has any objections, please let me know. ------------------ From: David Daney commit 46011e6ea39235e4aca656673c500eac81a07a17 upstream. On MIPS the GLOBAL bit of the PTE must have the same value in any aligned pair of PTEs. These pairs of PTEs are referred to as "buddies". In a SMP system is is possible for two CPUs to be calling set_pte() on adjacent PTEs at the same time. There is a race between setting the PTE and a different CPU setting the GLOBAL bit in its buddy PTE. This race can be observed when multiple CPUs are executing vmap()/vfree() at the same time. Make setting the buddy PTE's GLOBAL bit an atomic operation to close the race condition. The case of CONFIG_64BIT_PHYS_ADDR && CONFIG_CPU_MIPS32 is *not* handled. Signed-off-by: David Daney Cc: linux-mips@linux-mips.org Patchwork: https://patchwork.linux-mips.org/patch/10835/ Signed-off-by: Ralf Baechle Signed-off-by: Greg Kroah-Hartman --- arch/mips/include/asm/pgtable.h | 31 +++++++++++++++++++++++++++++++ 1 file changed, 31 insertions(+) --- a/arch/mips/include/asm/pgtable.h +++ b/arch/mips/include/asm/pgtable.h @@ -182,8 +182,39 @@ static inline void set_pte(pte_t *ptep, * Make sure the buddy is global too (if it's !none, * it better already be global) */ +#ifdef CONFIG_SMP + /* + * For SMP, multiple CPUs can race, so we need to do + * this atomically. + */ +#ifdef CONFIG_64BIT +#define LL_INSN "lld" +#define SC_INSN "scd" +#else /* CONFIG_32BIT */ +#define LL_INSN "ll" +#define SC_INSN "sc" +#endif + unsigned long page_global = _PAGE_GLOBAL; + unsigned long tmp; + + __asm__ __volatile__ ( + " .set push\n" + " .set noreorder\n" + "1: " LL_INSN " %[tmp], %[buddy]\n" + " bnez %[tmp], 2f\n" + " or %[tmp], %[tmp], %[global]\n" + " " SC_INSN " %[tmp], %[buddy]\n" + " beqz %[tmp], 1b\n" + " nop\n" + "2:\n" + " .set pop" + : [buddy] "+m" (buddy->pte), + [tmp] "=&r" (tmp) + : [global] "r" (page_global)); +#else /* !CONFIG_SMP */ if (pte_none(*buddy)) pte_val(*buddy) = pte_val(*buddy) | _PAGE_GLOBAL; +#endif /* CONFIG_SMP */ } #endif } -- 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/