From mboxrd@z Thu Jan 1 00:00:00 1970 From: Pan Xinhui Subject: [PATCH v7 01/11] kernel/sched: introduce vcpu preempted check interface Date: Wed, 2 Nov 2016 05:08:28 -0400 Message-ID: <1478077718-37424-2-git-send-email-xinhui.pan@linux.vnet.ibm.com> References: <1478077718-37424-1-git-send-email-xinhui.pan@linux.vnet.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: kernellwp@gmail.com, jgross@suse.com, dave@stgolabs.net, David.Laight@ACULAB.COM, rkrcmar@redhat.com, peterz@infradead.org, benh@kernel.crashing.org, konrad.wilk@oracle.com, will.deacon@arm.com, Pan Xinhui , mingo@redhat.com, paulus@samba.org, mpe@ellerman.id.au, pbonzini@redhat.com, paulmck@linux.vnet.ibm.com, boqun.feng@gmail.com 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, xen-devel@lists.xenproject.org, x86@kernel.org Return-path: In-Reply-To: <1478077718-37424-1-git-send-email-xinhui.pan@linux.vnet.ibm.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: virtualization-bounces@lists.linux-foundation.org Errors-To: virtualization-bounces@lists.linux-foundation.org List-Id: kvm.vger.kernel.org This patch support to fix lock holder preemption issue. For kernel users, we could use bool vcpu_is_preempted(int cpu) to detect 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 preempted check. Suggested-by: Peter Zijlstra (Intel) Signed-off-by: Pan Xinhui Acked-by: Christian Borntraeger Acked-by: Paolo Bonzini Tested-by: Juergen Gross --- include/linux/sched.h | 12 ++++++++++++ 1 file changed, 12 insertions(+) diff --git a/include/linux/sched.h b/include/linux/sched.h index 348f51b..44c1ce7 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -3506,6 +3506,18 @@ 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