From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Google-Smtp-Source: AB8JxZoIdj9LXVv28eYQLFmQF6djqiYHbbF5+/V3akTpy9As0btTqHiu2GG/YDEjMCNM9m8ybNLC ARC-Seal: i=1; a=rsa-sha256; t=1526417361; cv=none; d=google.com; s=arc-20160816; b=IQDILvBceTZXw5hDv+Z8ce0cUQ/0HZ7Ql5LUQtozmeMvvJ+wJGYdLFtx3DFm2lxUgV fLWZ+Dkp8Egob1fZNNrRfe52PoHxI2la6uEEmldMCHU/7Yj58ghuLoSPQ+KlUNckp6sv uAGzUWKxrN0M5a4ccWPXZ+MBFam7RM1M1fm20I5LGuFubr/Vlf17cMq0dwRKEpTRNN6q LDLaQXHTiTQEXdFv7eXyi5yaEDnU2b33Ck21v+qjHM3NH/2nDLmCBh0HtT4aBdA+ZRH0 WEjKX9MnytvWyQ0bGfTLmfYnNXFvzfUlOLiKK1dt38r61lRD+NZnZfzAaP6UyIuxhhH8 JGlg== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=precedence:content-disposition:content-transfer-encoding :mime-version:robot-unsubscribe:robot-id:git-commit-id:subject:to :references:in-reply-to:reply-to:cc:message-id:from:sender:date :arc-authentication-results; bh=EksQlChVjXS+aX6vrrT5i7qDci1wcgpKhJWQLeqNWC4=; b=DYv5uhgGyxUHfYc1Mc2zrbbl17p8cgYxlZhFBdYoUsy+5/Coh5iIR7cAOmlMrIYW6a B0JaOtwcsbTYg3nbxHMOlzcs4gL6jMaVjzBbmMrmyY2zjxqljVPV2gMCcBcatMCdfFgl 3bh/SVnZoarynbIO9kh12f3wHCD6UAC48L+ihpo88PmgheM73HoVdjy2oslvaZqFOyv5 +JCgnp6oaKpb9V6C1LMXe1lmu9fuV33vVkiESBXyGG4/8DfxSlcPiHNFPo83OCregP0A mkhGAPx+WYgGT+/s4059GUMEh9iw2S7vS3pIxX5YxUAZrGG0ISunoHz9mGk0SALXK5Pw n04A== ARC-Authentication-Results: i=1; mx.google.com; spf=pass (google.com: domain of tipbot@zytor.com designates 198.137.202.136 as permitted sender) smtp.mailfrom=tipbot@zytor.com Authentication-Results: mx.google.com; spf=pass (google.com: domain of tipbot@zytor.com designates 198.137.202.136 as permitted sender) smtp.mailfrom=tipbot@zytor.com Date: Tue, 15 May 2018 13:48:55 -0700 Sender: tip tree robot From: tip-bot for Dexuan Cui Message-ID: Cc: tglx@linutronix.de, fweisbec@gmail.com, kys@microsoft.com, dvyukov@google.com, adobriyan@gmail.com, gregkh@linuxfoundation.org, linux-kernel@vger.kernel.org, mingo@kernel.org, akpm@linux-foundation.org, torvalds@linux-foundation.org, rakib.mullick@gmail.com, decui@microsoft.com, Michael.H.Kelley@microsoft.com, hpa@zytor.com, jopoulso@microsoft.com, peterz@infradead.org, Jork.Loeser@microsoft.com Reply-To: Jork.Loeser@microsoft.com, peterz@infradead.org, jopoulso@microsoft.com, hpa@zytor.com, Michael.H.Kelley@microsoft.com, decui@microsoft.com, rakib.mullick@gmail.com, torvalds@linux-foundation.org, akpm@linux-foundation.org, mingo@kernel.org, linux-kernel@vger.kernel.org, gregkh@linuxfoundation.org, adobriyan@gmail.com, dvyukov@google.com, kys@microsoft.com, fweisbec@gmail.com, tglx@linutronix.de In-Reply-To: References: To: linux-tip-commits@vger.kernel.org Subject: [tip:timers/urgent] tick/broadcast: Use for_each_cpu() specially on UP kernels Git-Commit-ID: 5596fe34495cf0f645f417eb928ef224df3e3cb4 X-Mailer: tip-git-log-daemon Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: =?utf-8?q?1600561072875598164?= X-GMAIL-MSGID: =?utf-8?q?1600564611594293463?= X-Mailing-List: linux-kernel@vger.kernel.org List-ID: Commit-ID: 5596fe34495cf0f645f417eb928ef224df3e3cb4 Gitweb: https://git.kernel.org/tip/5596fe34495cf0f645f417eb928ef224df3e3cb4 Author: Dexuan Cui AuthorDate: Tue, 15 May 2018 19:52:50 +0000 Committer: Thomas Gleixner CommitDate: Tue, 15 May 2018 22:45:54 +0200 tick/broadcast: Use for_each_cpu() specially on UP kernels 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 --- kernel/time/tick-broadcast.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/kernel/time/tick-broadcast.c b/kernel/time/tick-broadcast.c index b398c2ea69b2..aa2094d5dd27 100644 --- a/kernel/time/tick-broadcast.c +++ b/kernel/time/tick-broadcast.c @@ -612,6 +612,14 @@ static void tick_handle_oneshot_broadcast(struct clock_event_device *dev) 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);