From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Cyrus-Session-Id: sloti22d1t05-2179907-1518719980-2-12711411955496490606 X-Sieve: CMU Sieve 3.0 X-Spam-known-sender: no X-Spam-score: 0.0 X-Spam-hits: BAYES_00 -1.9, HEADER_FROM_DIFFERENT_DOMAINS 0.001, ME_NOAUTH 0.01, RCVD_IN_DNSWL_HI -5, T_RP_MATCHES_RCVD -0.01, LANGUAGES en, BAYES_USED global, SA_VERSION 3.4.0 X-Spam-source: IP='209.132.180.67', Host='vger.kernel.org', Country='US', FromHeader='org', MailFrom='org' X-Spam-charsets: plain='UTF-8' X-Resolved-to: greg@kroah.com X-Delivered-to: greg@kroah.com X-Mail-from: stable-owner@vger.kernel.org ARC-Seal: i=1; a=rsa-sha256; cv=none; d=messagingengine.com; s=arctest; t=1518719979; b=AiwFEtXpO19Vtq6cxdNa3863AFGN+/yAHbgNyEVk5vYA0/w A4HeJudLxp4bITFXgDTxFkugzIElhvLRdynlE3r+43wX4h/5xaAKDCOJkxR/u+xX VdRJqkZmL3Wxh4mCv+ZLF/aAGUlN3ie7Yzg+uWar/9ko0eVZj5C/c9CaZDU9dDMp gOHiEpv/3J7n/DX1+NNgnYjkWQhBlEqi2wSYDqiBqPGtTUK7App8bDUxfe3ni4xb JWU08bAQZW7w5kfd9xT3vyvY4X8nt3gNHTUp6vng5JnaWxgLcwmXD4oYQGM1o0lv 5iJNQTggk+Qg00W7bq9Lw5Y/NCqDNp5dOspAw9Q== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d= messagingengine.com; h=from:to:cc:subject:date:message-id :in-reply-to:references:mime-version:content-type:sender :list-id; s=arctest; t=1518719979; bh=EEqrx9VPEpjFUDJNaFtdc2qD3i YIxBHg+YdgZNoLdmI=; b=UrKoAtns/6EG3CMOmeFU8c/Ej0r7m/97Niv83uoAwj UJTzaaNMGqOFQ22aHSep4NnrmjHtlGaym9Sa5gfoMOSKVlxLa5Z5f+0tnqhggRal lc4wbUwkHNjklhj2Cs6CfLrxEuGr7DV0bqfVzD7UBH87vXWmo1inLcZ9rs9xymLs mtlUbP7z99toZGtZhkxzMRKrLrfuGqAt7Vlx8GTzXQRbMH9PlwrMkJJTKKzzquKe SwbsFaroZOdFPVx3vU7XafOSct+NhY7XFmiYa8ZXxXFtA3RjhY5we/LmnrO9XqtS IPv3iw73i2shOTtvRhcIWEGq6UXw2nXiW7bEDIx0hTwg== ARC-Authentication-Results: i=1; mx2.messagingengine.com; arc=none (no signatures found); dkim=none (no signatures found); dmarc=none (p=none,has-list-id=yes,d=none) header.from=linuxfoundation.org; iprev=pass policy.iprev=209.132.180.67 (vger.kernel.org); spf=none smtp.mailfrom=stable-owner@vger.kernel.org smtp.helo=vger.kernel.org; x-aligned-from=fail; x-ptr=pass x-ptr-helo=vger.kernel.org x-ptr-lookup=vger.kernel.org; x-return-mx=pass smtp.domain=vger.kernel.org smtp.result=pass smtp_org.domain=kernel.org smtp_org.result=pass smtp_is_org_domain=no header.domain=linuxfoundation.org header.result=pass header_is_org_domain=yes Authentication-Results: mx2.messagingengine.com; arc=none (no signatures found); dkim=none (no signatures found); dmarc=none (p=none,has-list-id=yes,d=none) header.from=linuxfoundation.org; iprev=pass policy.iprev=209.132.180.67 (vger.kernel.org); spf=none smtp.mailfrom=stable-owner@vger.kernel.org smtp.helo=vger.kernel.org; x-aligned-from=fail; x-ptr=pass x-ptr-helo=vger.kernel.org x-ptr-lookup=vger.kernel.org; x-return-mx=pass smtp.domain=vger.kernel.org smtp.result=pass smtp_org.domain=kernel.org smtp_org.result=pass smtp_is_org_domain=no header.domain=linuxfoundation.org header.result=pass header_is_org_domain=yes Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1162739AbeBOPXv (ORCPT ); Thu, 15 Feb 2018 10:23:51 -0500 Received: from mail.linuxfoundation.org ([140.211.169.12]:51576 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1162733AbeBOPXp (ORCPT ); Thu, 15 Feb 2018 10:23:45 -0500 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Pavan Kondeti , "Steven Rostedt (VMware)" , "Peter Zijlstra (Intel)" , Andrew Morton , Linus Torvalds , Mike Galbraith , Thomas Gleixner , Ingo Molnar Subject: [PATCH 4.4 050/108] sched/rt: Up the root domain ref count when passing it around via IPIs Date: Thu, 15 Feb 2018 16:16:47 +0100 Message-Id: <20180215151229.400560633@linuxfoundation.org> X-Mailer: git-send-email 2.16.1 In-Reply-To: <20180215151222.267507937@linuxfoundation.org> References: <20180215151222.267507937@linuxfoundation.org> User-Agent: quilt/0.65 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: stable-owner@vger.kernel.org X-Mailing-List: stable@vger.kernel.org X-getmail-retrieved-from-mailbox: INBOX X-Mailing-List: linux-kernel@vger.kernel.org List-ID: 4.4-stable review patch. If anyone has any objections, please let me know. ------------------ From: Steven Rostedt (VMware) commit 364f56653708ba8bcdefd4f0da2a42904baa8eeb upstream. When issuing an IPI RT push, where an IPI is sent to each CPU that has more than one RT task scheduled on it, it references the root domain's rto_mask, that contains all the CPUs within the root domain that has more than one RT task in the runable state. The problem is, after the IPIs are initiated, the rq->lock is released. This means that the root domain that is associated to the run queue could be freed while the IPIs are going around. Add a sched_get_rd() and a sched_put_rd() that will increment and decrement the root domain's ref count respectively. This way when initiating the IPIs, the scheduler will up the root domain's ref count before releasing the rq->lock, ensuring that the root domain does not go away until the IPI round is complete. Reported-by: Pavan Kondeti Signed-off-by: Steven Rostedt (VMware) Signed-off-by: Peter Zijlstra (Intel) Cc: Andrew Morton Cc: Linus Torvalds Cc: Mike Galbraith Cc: Peter Zijlstra Cc: Thomas Gleixner Fixes: 4bdced5c9a292 ("sched/rt: Simplify the IPI based RT balancing logic") Link: http://lkml.kernel.org/r/CAEU1=PkiHO35Dzna8EQqNSKW1fr1y1zRQ5y66X117MG06sQtNA@mail.gmail.com Signed-off-by: Ingo Molnar Signed-off-by: Greg Kroah-Hartman --- kernel/sched/core.c | 13 +++++++++++++ kernel/sched/rt.c | 9 +++++++-- kernel/sched/sched.h | 2 ++ 3 files changed, 22 insertions(+), 2 deletions(-) --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -5896,6 +5896,19 @@ static void rq_attach_root(struct rq *rq call_rcu_sched(&old_rd->rcu, free_rootdomain); } +void sched_get_rd(struct root_domain *rd) +{ + atomic_inc(&rd->refcount); +} + +void sched_put_rd(struct root_domain *rd) +{ + if (!atomic_dec_and_test(&rd->refcount)) + return; + + call_rcu_sched(&rd->rcu, free_rootdomain); +} + static int init_rootdomain(struct root_domain *rd) { memset(rd, 0, sizeof(*rd)); --- a/kernel/sched/rt.c +++ b/kernel/sched/rt.c @@ -1916,8 +1916,11 @@ static void tell_cpu_to_push(struct rq * rto_start_unlock(&rq->rd->rto_loop_start); - if (cpu >= 0) + if (cpu >= 0) { + /* Make sure the rd does not get freed while pushing */ + sched_get_rd(rq->rd); irq_work_queue_on(&rq->rd->rto_push_work, cpu); + } } /* Called from hardirq context */ @@ -1947,8 +1950,10 @@ void rto_push_irq_work_func(struct irq_w raw_spin_unlock(&rd->rto_lock); - if (cpu < 0) + if (cpu < 0) { + sched_put_rd(rd); return; + } /* Try the next RT overloaded CPU */ irq_work_queue_on(&rd->rto_push_work, cpu); --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -553,6 +553,8 @@ struct root_domain { }; extern struct root_domain def_root_domain; +extern void sched_get_rd(struct root_domain *rd); +extern void sched_put_rd(struct root_domain *rd); #ifdef HAVE_RT_PUSH_IPI extern void rto_push_irq_work_func(struct irq_work *work);