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[209.132.180.67]) by mx.google.com with ESMTP id r63si564703pfg.653.2017.08.11.07.18.55; Fri, 11 Aug 2017 07:18:55 -0700 (PDT) Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67; Authentication-Results: mx.google.com; dkim=pass header.i=@linaro.org header.s=google header.b=VYD2oQdh; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=linaro.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753218AbdHKOSv (ORCPT + 25 others); Fri, 11 Aug 2017 10:18:51 -0400 Received: from mail-wr0-f178.google.com ([209.85.128.178]:38054 "EHLO mail-wr0-f178.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753080AbdHKOSr (ORCPT ); Fri, 11 Aug 2017 10:18:47 -0400 Received: by mail-wr0-f178.google.com with SMTP id f21so13852018wrf.5 for ; Fri, 11 Aug 2017 07:18:46 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; h=from:to:cc:subject:date:message-id:in-reply-to:references; bh=nDqlsJhUAk3IfHV4KCdccVXblqleBeW/0mVFD/7+on0=; b=VYD2oQdh9fa4LRzLJr1At+IQufQZVtUxvvauMcnFU6LWLQ5Skp8CqKYjUUdtoLPrAi E10b2AJcHepMEUMWtFGZHUUZWH45t9xE4QTwREikrC2iyqtNafwU4oRz2lCOZMbHju03 5YE/UoaasO9LbxrxLgySlLXVO7DXlryFr4N10= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references; bh=nDqlsJhUAk3IfHV4KCdccVXblqleBeW/0mVFD/7+on0=; b=nFHxdWzwxUV+NWPsBaJeMpfdXKHV5ZEBRZMN1Mj4Ej5G8LuVPLAWkLfVsYzq/SI/Ah dfquOU8rH+C7vmNOC1IA/bghL6xGGYSKtgmKz4smz+Z02JrrOb/NSrYB2bWWumrbo2Ez KxICJK1so7dQrByegfH4kSBzWIykKZxdNPrtxsTtoodtx862qd5T7Uz75+Cdnu3uSpn2 7BHEn2cz+VD04Uvsw+yoGvaa+/KjiO5jlExqxR1Atf0phHqYZysJNXGKBmSM3IwpL327 lcrwlD2xH7rJbPq/a+etPU8bT8sJ4IY98G95TQtie1Gb8ptz1/lUK53Y4EZGfyFnfd13 8ErA== X-Gm-Message-State: AHYfb5g6rFhEzEsEeFTSarwDzf2dHaHqssVUdt+EtUk0sCXIOwAhD+Tv twCEv399E3W+R+RE X-Received: by 10.223.171.17 with SMTP id q17mr12110724wrc.12.1502461125940; Fri, 11 Aug 2017 07:18:45 -0700 (PDT) Received: from localhost.localdomain ([2a01:e35:879a:6cd0:e0e8:7a5e:bd6d:f842]) by smtp.gmail.com with ESMTPSA id v22sm868383wra.70.2017.08.11.07.18.44 (version=TLS1_2 cipher=ECDHE-RSA-AES128-SHA bits=128/128); Fri, 11 Aug 2017 07:18:45 -0700 (PDT) From: Daniel Lezcano To: tglx@linutronix.de, mingo@kernel.org Cc: dingtianhong@huawei.com, matt.redfearn@imgtec.com, dan.carpenter@oracle.com, garsilva@embeddedor.com, mka@chromium.org, linux-kernel@vger.kernel.org, Mark Rutland , Marc Zyngier , Catalin Marinas , Will Deacon , linux-arm-kernel@lists.infradead.org (moderated list:ARM ARCHITECTED TIMER DRIVER) Subject: [PATCH 5/5] clocksource/drivers/arm_arch_timer: Avoid infinite recursion when ftrace is enabled Date: Fri, 11 Aug 2017 16:17:41 +0200 Message-Id: <1502461061-28065-5-git-send-email-daniel.lezcano@linaro.org> X-Mailer: git-send-email 2.7.4 In-Reply-To: <1502461061-28065-1-git-send-email-daniel.lezcano@linaro.org> References: <20170811141520.GA795@mai> <1502461061-28065-1-git-send-email-daniel.lezcano@linaro.org> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Ding Tianhong On platforms with an arch timer erratum workaround, it's possible for arch_timer_reg_read_stable() to recurse into itself when certain tracing options are enabled, leading to stack overflows and related problems. For example, when PREEMPT_TRACER and FUNCTION_GRAPH_TRACER are selected, it's possible to trigger this with: $ mount -t debugfs nodev /sys/kernel/debug/ $ echo function_graph > /sys/kernel/debug/tracing/current_tracer The problem is that in such cases, preempt_disable() instrumentation attempts to acquire a timestamp via trace_clock(), resulting in a call back to arch_timer_reg_read_stable(), and hence recursion. This patch changes arch_timer_reg_read_stable() to use preempt_{disable,enable}_notrace(), which avoids this. This problem is similar to the fixed by upstream commit 96b3d28bf4 ("sched/clock: Prevent tracing recursion in sched_clock_cpu()"). Fixes: 6acc71ccac71 ("arm64: arch_timer: Allows a CPU-specific erratum to only affect a subset of CPUs") Signed-off-by: Ding Tianhong Acked-by: Mark Rutland Acked-by: Marc Zyngier Signed-off-by: Daniel Lezcano --- arch/arm64/include/asm/arch_timer.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) -- 2.7.4 diff --git a/arch/arm64/include/asm/arch_timer.h b/arch/arm64/include/asm/arch_timer.h index 74d08e4..a652ce0 100644 --- a/arch/arm64/include/asm/arch_timer.h +++ b/arch/arm64/include/asm/arch_timer.h @@ -65,13 +65,13 @@ DECLARE_PER_CPU(const struct arch_timer_erratum_workaround *, u64 _val; \ if (needs_unstable_timer_counter_workaround()) { \ const struct arch_timer_erratum_workaround *wa; \ - preempt_disable(); \ + preempt_disable_notrace(); \ wa = __this_cpu_read(timer_unstable_counter_workaround); \ if (wa && wa->read_##reg) \ _val = wa->read_##reg(); \ else \ _val = read_sysreg(reg); \ - preempt_enable(); \ + preempt_enable_notrace(); \ } else { \ _val = read_sysreg(reg); \ } \