From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Google-Smtp-Source: AB8JxZqT2FCGkuT9YyTG3FdncMgY0/H7YiFAWoSX8VNypOcdbGJERmnf8JkvUpCKvI08z15dFDWW ARC-Seal: i=1; a=rsa-sha256; t=1526937858; cv=none; d=google.com; s=arc-20160816; b=Du9Mf0TpUnCT1kjIw6LpAVl0CDoiIL2zmAw9vC8JyOTM/1IsKXkQGgh1jb9Hvp6zek YJlpx3i+L7OROdqwBaDbMW7tQXzUk6mGmwqMeJNe1+HdQVo84eBzGs5bjrjUvC4Izf5S thFIo/+sFL6uImrLq1VExJtP+8siXgeCuh5OmJFPqYYzuXEFJ3dD7d1eOOF80bw4yf5Z HZ0Lfw3eMrliopf9Xp+NedsUzWaKjRZfSTsYAsMaKuFbinGoU2Afs8WqjY1veRKxug5e h3biemVft3TZrf42K0C7VkHWDkHM1u6uItr+qegMyvHVsw35OvClkFm++KRu1/TqmpmE 2KFg== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=mime-version:user-agent:references:in-reply-to:message-id:date :subject:cc:to:from:dkim-signature:arc-authentication-results; bh=K1kkr//HmVHsKbQygVFljizo4JApU5OUpk4rQYLVrek=; b=RK2uvN7SkpFTF1O9vCspAYHET+pQnKVsHkBJSPE+DCndbb+5SOs0GakDW8cH4P8qXa B6v8BvDUMo0mJnak1GSxeA+wNZu4gVyhjHEBpdrydeOZ84izjxV9KRGz8VQdGZvQoode Nfqy8stwu5jIGMBuLgiTKvZjxjKviZUHeeSHHgV11mZB/3XijQExchyStiU6chVXVwxb mAYe5VkybdKl64+dXhGTge7EuhN9WOql06ReTH4gnOGZsP/Lg5p8UV2uq2pfM9LjS0ej qFfWkJY4PgFA9qnr4WdCA3ap2Ry0tL0GJ6pslWytOpXvXufwi7Lv0m8oFB9DSCfKtolw 4CXA== ARC-Authentication-Results: i=1; mx.google.com; dkim=pass header.i=@kernel.org header.s=default header.b=g69PstjA; spf=pass (google.com: domain of srs0=nia/=ii=linuxfoundation.org=gregkh@kernel.org designates 198.145.29.99 as permitted sender) smtp.mailfrom=SRS0=nia/=II=linuxfoundation.org=gregkh@kernel.org Authentication-Results: mx.google.com; dkim=pass header.i=@kernel.org header.s=default header.b=g69PstjA; spf=pass (google.com: domain of srs0=nia/=ii=linuxfoundation.org=gregkh@kernel.org designates 198.145.29.99 as permitted sender) smtp.mailfrom=SRS0=nia/=II=linuxfoundation.org=gregkh@kernel.org From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Dexuan Cui , Thomas Gleixner , Josh Poulson , "Michael Kelley (EOSG)" , Peter Zijlstra , Frederic Weisbecker , Rakib Mullick , Jork Loeser , Andrew Morton , KY Srinivasan , Linus Torvalds , Alexey Dobriyan , Dmitry Vyukov Subject: [PATCH 4.16 051/110] tick/broadcast: Use for_each_cpu() specially on UP kernels Date: Mon, 21 May 2018 23:11:48 +0200 Message-Id: <20180521210509.649360269@linuxfoundation.org> X-Mailer: git-send-email 2.17.0 In-Reply-To: <20180521210503.823249477@linuxfoundation.org> References: <20180521210503.823249477@linuxfoundation.org> User-Agent: quilt/0.65 X-stable: review MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-LABELS: =?utf-8?b?IlxcU2VudCI=?= X-GMAIL-THRID: =?utf-8?q?1601109796027859618?= X-GMAIL-MSGID: =?utf-8?q?1601110391835874280?= X-Mailing-List: linux-kernel@vger.kernel.org List-ID: 4.16-stable review patch. If anyone has any objections, please let me know. ------------------ From: Dexuan Cui commit 5596fe34495cf0f645f417eb928ef224df3e3cb4 upstream. for_each_cpu() unintuitively reports CPU0 as set independent of the actual cpumask content on UP kernels. This causes an unexpected PIT interrupt storm on a UP kernel running in an SMP virtual machine on Hyper-V, and as a result, the virtual machine can suffer from a strange random delay of 1~20 minutes during boot-up, and sometimes it can hang forever. Protect if by checking whether the cpumask is empty before entering the for_each_cpu() loop. [ tglx: Use !IS_ENABLED(CONFIG_SMP) instead of #ifdeffery ] Signed-off-by: Dexuan Cui Signed-off-by: Thomas Gleixner Cc: Josh Poulson Cc: "Michael Kelley (EOSG)" Cc: Peter Zijlstra Cc: Frederic Weisbecker Cc: stable@vger.kernel.org Cc: Rakib Mullick Cc: Jork Loeser Cc: Greg Kroah-Hartman Cc: Andrew Morton Cc: KY Srinivasan Cc: Linus Torvalds Cc: Alexey Dobriyan Cc: Dmitry Vyukov Link: https://lkml.kernel.org/r/KL1P15301MB000678289FE55BA365B3279ABF990@KL1P15301MB0006.APCP153.PROD.OUTLOOK.COM Link: https://lkml.kernel.org/r/KL1P15301MB0006FA63BC22BEB64902EAA0BF930@KL1P15301MB0006.APCP153.PROD.OUTLOOK.COM Signed-off-by: Greg Kroah-Hartman --- kernel/time/tick-broadcast.c | 8 ++++++++ 1 file changed, 8 insertions(+) --- a/kernel/time/tick-broadcast.c +++ b/kernel/time/tick-broadcast.c @@ -612,6 +612,14 @@ static void tick_handle_oneshot_broadcas now = ktime_get(); /* Find all expired events */ for_each_cpu(cpu, tick_broadcast_oneshot_mask) { + /* + * Required for !SMP because for_each_cpu() reports + * unconditionally CPU0 as set on UP kernels. + */ + if (!IS_ENABLED(CONFIG_SMP) && + cpumask_empty(tick_broadcast_oneshot_mask)) + break; + td = &per_cpu(tick_cpu_device, cpu); if (td->evtdev->next_event <= now) { cpumask_set_cpu(cpu, tmpmask);