From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail144.messagelabs.com (mail144.messagelabs.com [216.82.254.51]) by kanga.kvack.org (Postfix) with SMTP id 7E8146B02CD for ; Tue, 24 Aug 2010 05:30:44 -0400 (EDT) Message-ID: <4C739131.1050203@redhat.com> Date: Tue, 24 Aug 2010 12:30:25 +0300 From: Avi Kivity MIME-Version: 1.0 Subject: Re: [PATCH v5 10/12] Handle async PF in non preemptable context References: <1279553462-7036-1-git-send-email-gleb@redhat.com> <1279553462-7036-11-git-send-email-gleb@redhat.com> In-Reply-To: <1279553462-7036-11-git-send-email-gleb@redhat.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org To: Gleb Natapov Cc: kvm@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, mingo@elte.hu, a.p.zijlstra@chello.nl, tglx@linutronix.de, hpa@zytor.com, riel@redhat.com, cl@linux-foundation.org, mtosatti@redhat.com List-ID: On 07/19/2010 06:31 PM, Gleb Natapov wrote: > If async page fault is received by idle task or when preemp_count is > not zero guest cannot reschedule, so do sti; hlt and wait for page to be > ready. vcpu can still process interrupts while it waits for the page to > be ready. > > Acked-by: Rik van Riel > Signed-off-by: Gleb Natapov > --- > arch/x86/kernel/kvm.c | 36 ++++++++++++++++++++++++++++++++---- > 1 files changed, 32 insertions(+), 4 deletions(-) > > diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c > index a6db92e..914b0fc 100644 > --- a/arch/x86/kernel/kvm.c > +++ b/arch/x86/kernel/kvm.c > @@ -37,6 +37,7 @@ > #include > #include > #include > +#include > > #define MMU_QUEUE_SIZE 1024 > > @@ -68,6 +69,8 @@ struct kvm_task_sleep_node { > wait_queue_head_t wq; > u32 token; > int cpu; > + bool halted; > + struct mm_struct *mm; > }; > > static struct kvm_task_sleep_head { > @@ -96,6 +99,11 @@ static void apf_task_wait(struct task_struct *tsk, u32 token) > struct kvm_task_sleep_head *b =&async_pf_sleepers[key]; > struct kvm_task_sleep_node n, *e; > DEFINE_WAIT(wait); > + int cpu, idle; > + > + cpu = get_cpu(); > + idle = idle_cpu(cpu); > + put_cpu(); > > spin_lock(&b->lock); > e = _find_apf_task(b, token); > @@ -109,17 +117,31 @@ static void apf_task_wait(struct task_struct *tsk, u32 token) > > n.token = token; > n.cpu = smp_processor_id(); > + n.mm = current->active_mm; > + n.halted = idle || preempt_count()> 1; > + atomic_inc(&n.mm->mm_count); > init_waitqueue_head(&n.wq); > hlist_add_head(&n.link,&b->list); > spin_unlock(&b->lock); > > for (;;) { > - prepare_to_wait(&n.wq,&wait, TASK_UNINTERRUPTIBLE); > + if (!n.halted) > + prepare_to_wait(&n.wq,&wait, TASK_UNINTERRUPTIBLE); > if (hlist_unhashed(&n.link)) > break; > - schedule(); > + > + if (!n.halted) { > + schedule(); > + } else { > + /* > + * We cannot reschedule. So halt. > + */ If we get the wakeup here, we'll halt and never wake up again. > + native_safe_halt(); > + local_irq_disable(); So we need a local_irq_disable() before the hlish_unhashed() check. > + } > } > - finish_wait(&n.wq,&wait); > + if (!n.halted) > + finish_wait(&n.wq,&wait); > > return; > } > @@ -127,7 +149,12 @@ static void apf_task_wait(struct task_struct *tsk, u32 token) > static void apf_task_wake_one(struct kvm_task_sleep_node *n) > { > hlist_del_init(&n->link); > - if (waitqueue_active(&n->wq)) > + if (!n->mm) > + return; > + mmdrop(n->mm); > + if (n->halted) > + smp_send_reschedule(n->cpu); > + else if (waitqueue_active(&n->wq)) > wake_up(&n->wq); > } > > @@ -157,6 +184,7 @@ again: > } > n->token = token; > n->cpu = smp_processor_id(); > + n->mm = NULL; > init_waitqueue_head(&n->wq); > hlist_add_head(&n->link,&b->list); > } else -- error compiling committee.c: too many arguments to function -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org