From patchwork Thu Jul 25 08:16:25 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Masami Hiramatsu (Google)" X-Patchwork-Id: 11058205 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id AFF6D13AC for ; Thu, 25 Jul 2019 08:17:53 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 9FEB4287E2 for ; Thu, 25 Jul 2019 08:17:53 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 90B89287FE; Thu, 25 Jul 2019 08:17:53 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.2 required=2.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,MAILING_LIST_MULTI,RCVD_IN_DNSWL_MED autolearn=ham version=3.3.1 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.wl.linuxfoundation.org (Postfix) with ESMTPS id 3AF8A287E2 for ; Thu, 25 Jul 2019 08:17:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:MIME-Version:References:In-Reply-To: Message-Id:Date:Subject:To:From:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=sPMEhCBq7kyKq00eA01e8EA5Tz9m3ZfLthXVKbgRJFo=; b=pNWv49uB8w+CT3 2YPqUt+3wt/8Si7GOb4R4nyhGSWK1wl4piFjG2a6mGi6ZitCngqZTLSkpdxSEDAHWWtMCLR3IdAEj LXAousCFJ0PxCcs4HM+WzfmE823xMh+25iiCEm3L4jTNyndibgf08eJc3tp/VC8gh9gPswcL+vkoN D8vxR9ik/TbGjESROQBcUD6gWdJqkXh4vAWjE/i4dkAwwKL8ri5n7o1vQmtxga61G5x8+bg0V87cE OF6Wf3SYzYEIMZ0+vz59bj1qQdxkagVKP9LTVjLaym/w0EcJQfSvC3G5zYr71hYR629V8hU605G3n NoHdEpzay4ajMNeKhxvw==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92 #3 (Red Hat Linux)) id 1hqYwi-0004q3-EM; Thu, 25 Jul 2019 08:17:52 +0000 Received: from mail.kernel.org ([198.145.29.99]) by bombadil.infradead.org with esmtps (Exim 4.92 #3 (Red Hat Linux)) id 1hqYvO-00043m-MO for linux-arm-kernel@lists.infradead.org; Thu, 25 Jul 2019 08:16:34 +0000 Received: from localhost.localdomain (NE2965lan1.rev.em-net.ne.jp [210.141.244.193]) (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 F351820657; Thu, 25 Jul 2019 08:16:27 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1564042590; bh=U5JsQy9M6SP8lvveNoBirJFjzlJL4CpLUxow+e3YRvo=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=bXA7Rl4m1FdAnDljrSpbxyNrTH2z8iih7Q6dNDIACq/JZ2YEq6oyUBvUr6O4tztZK 0C++xAFHag/f4QcJPiuQfC4xCDiH0v4SAqAfBopH46lPyCOKPKYs/Q4YwUtX8nD+SE p5/l8oVtssyFD3TRWXmyN0IPESb1pyg1C8xqZyeE= From: Masami Hiramatsu To: Catalin Marinas , Will Deacon Subject: [PATCH v3 4/4] arm64: Remove unneeded rcu_read_lock from debug handlers Date: Thu, 25 Jul 2019 17:16:25 +0900 Message-Id: <156404258547.2020.3652813018925680357.stgit@devnote2> X-Mailer: git-send-email 2.20.1 In-Reply-To: <156404254387.2020.886452004489353899.stgit@devnote2> References: <156404254387.2020.886452004489353899.stgit@devnote2> User-Agent: StGit/0.17.1-dirty MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190725_011632_440479_DBA79078 X-CRM114-Status: GOOD ( 11.75 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Dan Rue , Daniel Diaz , Anders Roxell , Naresh Kamboju , linux-kernel@vger.kernel.org, Matt Hart , "Paul E . McKenney" , linux-arm-kernel@lists.infradead.org, mhiramat@kernel.org Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org X-Virus-Scanned: ClamAV using ClamSMTP Remove rcu_read_lock()/rcu_read_unlock() from debug exception handlers since we are sure those are not preemptible and interrupts are off. Acked-by: Paul E. McKenney Signed-off-by: Masami Hiramatsu --- arch/arm64/kernel/debug-monitors.c | 14 ++++++++------ 1 file changed, 8 insertions(+), 6 deletions(-) diff --git a/arch/arm64/kernel/debug-monitors.c b/arch/arm64/kernel/debug-monitors.c index f8719bd30850..48222a4760c2 100644 --- a/arch/arm64/kernel/debug-monitors.c +++ b/arch/arm64/kernel/debug-monitors.c @@ -207,16 +207,16 @@ static int call_step_hook(struct pt_regs *regs, unsigned int esr) list = user_mode(regs) ? &user_step_hook : &kernel_step_hook; - rcu_read_lock(); - + /* + * Since single-step exception disables interrupt, this function is + * entirely not preemptible, and we can use rcu list safely here. + */ list_for_each_entry_rcu(hook, list, node) { retval = hook->fn(regs, esr); if (retval == DBG_HOOK_HANDLED) break; } - rcu_read_unlock(); - return retval; } NOKPROBE_SYMBOL(call_step_hook); @@ -305,14 +305,16 @@ static int call_break_hook(struct pt_regs *regs, unsigned int esr) list = user_mode(regs) ? &user_break_hook : &kernel_break_hook; - rcu_read_lock(); + /* + * Since brk exception disables interrupt, this function is + * entirely not preemptible, and we can use rcu list safely here. + */ list_for_each_entry_rcu(hook, list, node) { unsigned int comment = esr & ESR_ELx_BRK64_ISS_COMMENT_MASK; if ((comment & ~hook->mask) == hook->imm) fn = hook->fn; } - rcu_read_unlock(); return fn ? fn(regs, esr) : DBG_HOOK_ERROR; }