From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx0a-001b2d01.pphosted.com (mx0b-001b2d01.pphosted.com [148.163.158.5]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 3rw5Sn1KngzDqSQ for ; Thu, 21 Jul 2016 17:46:32 +1000 (AEST) Received: from pps.filterd (m0098417.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.11/8.16.0.11) with SMTP id u6L7iMPB015907 for ; Thu, 21 Jul 2016 03:46:30 -0400 Received: from e17.ny.us.ibm.com (e17.ny.us.ibm.com [129.33.205.207]) by mx0a-001b2d01.pphosted.com with ESMTP id 24as6fjdwx-1 (version=TLSv1.2 cipher=AES256-SHA bits=256 verify=NOT) for ; Thu, 21 Jul 2016 03:46:30 -0400 Received: from localhost by e17.ny.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Thu, 21 Jul 2016 03:46:29 -0400 From: Pan Xinhui To: linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, virtualization@lists.linux-foundation.org, linux-s390@vger.kernel.org, xen-devel-request@lists.xenproject.org, kvm@vger.kernel.org Cc: benh@kernel.crashing.org, paulus@samba.org, mpe@ellerman.id.au, mingo@redhat.com, peterz@infradead.org, paulmck@linux.vnet.ibm.com, will.deacon@arm.com, kernellwp@gmail.com, jgross@suse.com, pbonzini@redhat.com, bsingharora@gmail.com, Pan Xinhui Subject: [PATCH v3 1/4] kernel/sched: introduce vcpu preempted check interface Date: Thu, 21 Jul 2016 07:45:11 -0400 In-Reply-To: <1469101514-49475-1-git-send-email-xinhui.pan@linux.vnet.ibm.com> References: <1469101514-49475-1-git-send-email-xinhui.pan@linux.vnet.ibm.com> Message-Id: <1469101514-49475-2-git-send-email-xinhui.pan@linux.vnet.ibm.com> List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , This patch supports to fix lock holder preemption issue. For kernel users, we could use bool vcpu_is_preempted(int cpu) to detech if one vcpu is preempted or not. The default implementation is a macro defined by false. So compiler can wrap it out if arch dose not support such vcpu pteempted check. Suggested-by: Peter Zijlstra (Intel) Signed-off-by: Pan Xinhui --- include/linux/sched.h | 12 ++++++++++++ 1 file changed, 12 insertions(+) diff --git a/include/linux/sched.h b/include/linux/sched.h index 6e42ada..cbe0574 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -3293,6 +3293,18 @@ static inline void set_task_cpu(struct task_struct *p, unsigned int cpu) #endif /* CONFIG_SMP */ +/* + * In order to deal with a various lock holder preemption issues provide an + * interface to see if a vCPU is currently running or not. + * + * This allows us to terminate optimistic spin loops and block, analogous to + * the native optimistic spin heuristic of testing if the lock owner task is + * running or not. + */ +#ifndef vcpu_is_preempted +#define vcpu_is_preempted(cpu) false +#endif + extern long sched_setaffinity(pid_t pid, const struct cpumask *new_mask); extern long sched_getaffinity(pid_t pid, struct cpumask *mask); -- 2.4.11