lkml.org 
[lkml]   [2016]   [Sep]   [1]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    SubjectRe: [PATCH] KVM: Remove deprecated create_singlethread_workqueue
    From
    Date


    On 30/08/2016 19:59, Bhaktipriya Shridhar wrote:
    > The workqueue "irqfd_cleanup_wq" queues a single work item
    > &irqfd->shutdown and hence doesn't require ordering. It is a host-wide
    > workqueue for issuing deferred shutdown requests aggregated from all
    > vm* instances. It is not being used on a memory reclaim path.
    > Hence, it has been converted to use system_wq.
    > The work item has been flushed in kvm_irqfd_release().
    >
    > The workqueue "wqueue" queues a single work item &timer->expired
    > and hence doesn't require ordering. Also, it is not being used on
    > a memory reclaim path. Hence, it has been converted to use system_wq.
    >
    > System workqueues have been able to handle high level of concurrency
    > for a long time now and hence it's not required to have a singlethreaded
    > workqueue just to gain concurrency. Unlike a dedicated per-cpu workqueue
    > created with create_singlethread_workqueue(), system_wq allows multiple
    > work items to overlap executions even on the same CPU; however, a
    > per-cpu workqueue doesn't have any CPU locality or global ordering
    > guarantee unless the target CPU is explicitly specified and thus the
    > increase of local concurrency shouldn't make any difference.
    >
    > Signed-off-by: Bhaktipriya Shridhar <bhaktipriya96@gmail.com>
    > ---
    > virt/kvm/arm/arch_timer.c | 11 ++---------
    > virt/kvm/eventfd.c | 22 +++-------------------
    > virt/kvm/kvm_main.c | 6 ------
    > 3 files changed, 5 insertions(+), 34 deletions(-)
    >
    > diff --git a/virt/kvm/arm/arch_timer.c b/virt/kvm/arm/arch_timer.c
    > index e2d5b6f..56e0c15 100644
    > --- a/virt/kvm/arm/arch_timer.c
    > +++ b/virt/kvm/arm/arch_timer.c
    > @@ -31,7 +31,6 @@
    > #include "trace.h"
    >
    > static struct timecounter *timecounter;
    > -static struct workqueue_struct *wqueue;
    > static unsigned int host_vtimer_irq;
    >
    > void kvm_timer_vcpu_put(struct kvm_vcpu *vcpu)
    > @@ -140,7 +139,7 @@ static enum hrtimer_restart kvm_timer_expire(struct hrtimer *hrt)
    > return HRTIMER_RESTART;
    > }
    >
    > - queue_work(wqueue, &timer->expired);
    > + schedule_work(&timer->expired);
    > return HRTIMER_NORESTART;
    > }
    >
    > @@ -455,12 +454,6 @@ int kvm_timer_hyp_init(void)
    > goto out_free;
    > }
    >
    > - wqueue = create_singlethread_workqueue("kvm_arch_timer");
    > - if (!wqueue) {
    > - err = -ENOMEM;
    > - goto out_free;
    > - }
    > -
    > kvm_info("virtual timer IRQ%d\n", host_vtimer_irq);
    > on_each_cpu(kvm_timer_init_interrupt, NULL, 1);
    >
    > @@ -522,7 +515,7 @@ int kvm_timer_enable(struct kvm_vcpu *vcpu)
    > * VCPUs have the enabled variable set, before entering the guest, if
    > * the arch timers are enabled.
    > */
    > - if (timecounter && wqueue)
    > + if (timecounter)
    > timer->enabled = 1;
    >
    > return 0;
    > diff --git a/virt/kvm/eventfd.c b/virt/kvm/eventfd.c
    > index e469b60..f397e9b 100644
    > --- a/virt/kvm/eventfd.c
    > +++ b/virt/kvm/eventfd.c
    > @@ -42,7 +42,6 @@
    >
    > #ifdef CONFIG_HAVE_KVM_IRQFD
    >
    > -static struct workqueue_struct *irqfd_cleanup_wq;
    >
    > static void
    > irqfd_inject(struct work_struct *work)
    > @@ -168,7 +167,7 @@ irqfd_deactivate(struct kvm_kernel_irqfd *irqfd)
    >
    > list_del_init(&irqfd->list);
    >
    > - queue_work(irqfd_cleanup_wq, &irqfd->shutdown);
    > + schedule_work(&irqfd->shutdown);
    > }
    >
    > int __attribute__((weak)) kvm_arch_set_irq_inatomic(
    > @@ -555,7 +554,7 @@ kvm_irqfd_deassign(struct kvm *kvm, struct kvm_irqfd *args)
    > * so that we guarantee there will not be any more interrupts on this
    > * gsi once this deassign function returns.
    > */
    > - flush_workqueue(irqfd_cleanup_wq);
    > + flush_work(&irqfd->shutdown);
    >
    > return 0;
    > }
    > @@ -592,7 +591,7 @@ kvm_irqfd_release(struct kvm *kvm)
    > * Block until we know all outstanding shutdown jobs have completed
    > * since we do not take a kvm* reference.
    > */
    > - flush_workqueue(irqfd_cleanup_wq);
    > + flush_work(&irqfd->shutdown);
    >
    > }
    >
    > @@ -622,23 +621,8 @@ void kvm_irq_routing_update(struct kvm *kvm)
    > spin_unlock_irq(&kvm->irqfds.lock);
    > }
    >
    > -/*
    > - * create a host-wide workqueue for issuing deferred shutdown requests
    > - * aggregated from all vm* instances. We need our own isolated single-thread
    > - * queue to prevent deadlock against flushing the normal work-queue.
    > - */
    > -int kvm_irqfd_init(void)
    > -{
    > - irqfd_cleanup_wq = create_singlethread_workqueue("kvm-irqfd-cleanup");
    > - if (!irqfd_cleanup_wq)
    > - return -ENOMEM;
    > -
    > - return 0;
    > -}
    > -
    > void kvm_irqfd_exit(void)
    > {
    > - destroy_workqueue(irqfd_cleanup_wq);
    > }
    > #endif
    >
    > diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
    > index 02e98f3..93506d2 100644
    > --- a/virt/kvm/kvm_main.c
    > +++ b/virt/kvm/kvm_main.c
    > @@ -3719,12 +3719,7 @@ int kvm_init(void *opaque, unsigned vcpu_size, unsigned vcpu_align,
    > * kvm_arch_init makes sure there's at most one caller
    > * for architectures that support multiple implementations,
    > * like intel and amd on x86.
    > - * kvm_arch_init must be called before kvm_irqfd_init to avoid creating
    > - * conflicts in case kvm is already setup for another implementation.
    > */
    > - r = kvm_irqfd_init();
    > - if (r)
    > - goto out_irqfd;
    >
    > if (!zalloc_cpumask_var(&cpus_hardware_enabled, GFP_KERNEL)) {
    > r = -ENOMEM;
    > @@ -3805,7 +3800,6 @@ out_free_0a:
    > free_cpumask_var(cpus_hardware_enabled);
    > out_free_0:
    > kvm_irqfd_exit();
    > -out_irqfd:
    > kvm_arch_exit();
    > out_fail:
    > return r;
    > --
    > 2.1.4
    >

    Rebased (the virt/kvm/arm part doesn't apply anymore due to the CPU
    notifier refactoring) and applied, thanks.

    Paolo

    [unhandled content-type:application/pgp-signature]
    \
     
     \ /
      Last update: 2016-09-17 09:58    [W:4.290 / U:0.028 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site