Re: [PATCH] VMCI: Use threaded irqs instead of tasklets

From: Zack Rusin
Date: Wed Nov 30 2022 - 09:59:03 EST


On Tue, 2022-11-29 at 23:05 -0800, vdasa@xxxxxxxxxx wrote:
> From: Vishnu Dasa <vdasa@xxxxxxxxxx>
>
> The vmci_dispatch_dgs() tasklet function calls vmci_read_data()
> which uses wait_event() resulting in invalid sleep in an atomic
> context (and therefore potentially in a deadlock).
>
> Use threaded irqs to fix this issue and completely remove usage
> of tasklets.
>
> [   20.264639] BUG: sleeping function called from invalid context at
> drivers/misc/vmw_vmci/vmci_guest.c:145
> [   20.264643] in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 762, name:
> vmtoolsd
> [   20.264645] preempt_count: 101, expected: 0
> [   20.264646] RCU nest depth: 0, expected: 0
> [   20.264647] 1 lock held by vmtoolsd/762:
> [   20.264648]  #0: ffff0000874ae440 (sk_lock-AF_VSOCK){+.+.}-{0:0}, at:
> vsock_connect+0x60/0x330 [vsock]
> [   20.264658] Preemption disabled at:
> [   20.264659] [<ffff80000151d7d8>] vmci_send_datagram+0x44/0xa0 [vmw_vmci]
> [   20.264665] CPU: 0 PID: 762 Comm: vmtoolsd Not tainted 5.19.0-
> 0.rc8.20220727git39c3c396f813.60.fc37.aarch64 #1
> [   20.264667] Hardware name: VMware, Inc. VBSA/VBSA, BIOS VEFI 12/31/2020
> [   20.264668] Call trace:
> [   20.264669]  dump_backtrace+0xc4/0x130
> [   20.264672]  show_stack+0x24/0x80
> [   20.264673]  dump_stack_lvl+0x88/0xb4
> [   20.264676]  dump_stack+0x18/0x34
> [   20.264677]  __might_resched+0x1a0/0x280
> [   20.264679]  __might_sleep+0x58/0x90
> [   20.264681]  vmci_read_data+0x74/0x120 [vmw_vmci]
> [   20.264683]  vmci_dispatch_dgs+0x64/0x204 [vmw_vmci]
> [   20.264686]  tasklet_action_common.constprop.0+0x13c/0x150
> [   20.264688]  tasklet_action+0x40/0x50
> [   20.264689]  __do_softirq+0x23c/0x6b4
> [   20.264690]  __irq_exit_rcu+0x104/0x214
> [   20.264691]  irq_exit_rcu+0x1c/0x50
> [   20.264693]  el1_interrupt+0x38/0x6c
> [   20.264695]  el1h_64_irq_handler+0x18/0x24
> [   20.264696]  el1h_64_irq+0x68/0x6c
> [   20.264697]  preempt_count_sub+0xa4/0xe0
> [   20.264698]  _raw_spin_unlock_irqrestore+0x64/0xb0
> [   20.264701]  vmci_send_datagram+0x7c/0xa0 [vmw_vmci]
> [   20.264703]  vmci_datagram_dispatch+0x84/0x100 [vmw_vmci]
> [   20.264706]  vmci_datagram_send+0x2c/0x40 [vmw_vmci]
> [   20.264709]  vmci_transport_send_control_pkt+0xb8/0x120
> [vmw_vsock_vmci_transport]
> [   20.264711]  vmci_transport_connect+0x40/0x7c [vmw_vsock_vmci_transport]
> [   20.264713]  vsock_connect+0x278/0x330 [vsock]
> [   20.264715]  __sys_connect_file+0x8c/0xc0
> [   20.264718]  __sys_connect+0x84/0xb4
> [   20.264720]  __arm64_sys_connect+0x2c/0x3c
> [   20.264721]  invoke_syscall+0x78/0x100
> [   20.264723]  el0_svc_common.constprop.0+0x68/0x124
> [   20.264724]  do_el0_svc+0x38/0x4c
> [   20.264725]  el0_svc+0x60/0x180
> [   20.264726]  el0t_64_sync_handler+0x11c/0x150
> [   20.264728]  el0t_64_sync+0x190/0x194
>
> Signed-off-by: Vishnu Dasa <vdasa@xxxxxxxxxx>
> Suggested-by: Zack Rusin <zackr@xxxxxxxxxx>
> Reported-by: Nadav Amit <namit@xxxxxxxxxx>
> Reported-by: Nathan Chancellor <nathan@xxxxxxxxxx>
> Tested-by: Nathan Chancellor <nathan@xxxxxxxxxx>
> Fixes: 463713eb6164 ("VMCI: dma dg: add support for DMA datagrams receive")
> Cc: <stable@xxxxxxxxxxxxxxx> # v5.18+
> Cc: VMware PV-Drivers Reviewers <pv-drivers@xxxxxxxxxx>
> Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
> Cc: Bryan Tan <bryantan@xxxxxxxxxx>
> ---
>  drivers/misc/vmw_vmci/vmci_guest.c | 49 ++++++++++++------------------
>  1 file changed, 19 insertions(+), 30 deletions(-)
>
> diff --git a/drivers/misc/vmw_vmci/vmci_guest.c
> b/drivers/misc/vmw_vmci/vmci_guest.c
> index aa7b05de97dd..6ab717b4a5db 100644
> --- a/drivers/misc/vmw_vmci/vmci_guest.c
> +++ b/drivers/misc/vmw_vmci/vmci_guest.c
> @@ -56,8 +56,6 @@ struct vmci_guest_device {
>  
>         bool exclusive_vectors;
>  
> -       struct tasklet_struct datagram_tasklet;
> -       struct tasklet_struct bm_tasklet;
>         struct wait_queue_head inout_wq;
>  
>         void *data_buffer;
> @@ -304,9 +302,8 @@ static int vmci_check_host_caps(struct pci_dev *pdev)
>   * This function assumes that it has exclusive access to the data
>   * in register(s) for the duration of the call.
>   */
> -static void vmci_dispatch_dgs(unsigned long data)
> +static void vmci_dispatch_dgs(struct vmci_guest_device *vmci_dev)
>  {
> -       struct vmci_guest_device *vmci_dev = (struct vmci_guest_device *)data;
>         u8 *dg_in_buffer = vmci_dev->data_buffer;
>         struct vmci_datagram *dg;
>         size_t dg_in_buffer_size = VMCI_MAX_DG_SIZE;
> @@ -465,10 +462,8 @@ static void vmci_dispatch_dgs(unsigned long data)
>   * Scans the notification bitmap for raised flags, clears them
>   * and handles the notifications.
>   */
> -static void vmci_process_bitmap(unsigned long data)
> +static void vmci_process_bitmap(struct vmci_guest_device *dev)
>  {
> -       struct vmci_guest_device *dev = (struct vmci_guest_device *)data;
> -
>         if (!dev->notification_bitmap) {
>                 dev_dbg(dev->dev, "No bitmap present in %s\n", __func__);
>                 return;
> @@ -486,13 +481,13 @@ static irqreturn_t vmci_interrupt(int irq, void *_dev)
>         struct vmci_guest_device *dev = _dev;
>  
>         /*
> -        * If we are using MSI-X with exclusive vectors then we simply schedule
> -        * the datagram tasklet, since we know the interrupt was meant for us.
> +        * If we are using MSI-X with exclusive vectors then we simply call
> +        * vmci_dispatch_dgs(), since we know the interrupt was meant for us.
>          * Otherwise we must read the ICR to determine what to do.
>          */
>  
>         if (dev->exclusive_vectors) {
> -               tasklet_schedule(&dev->datagram_tasklet);
> +               vmci_dispatch_dgs(dev);
>         } else {
>                 unsigned int icr;
>  
> @@ -502,12 +497,12 @@ static irqreturn_t vmci_interrupt(int irq, void *_dev)
>                         return IRQ_NONE;
>  
>                 if (icr & VMCI_ICR_DATAGRAM) {
> -                       tasklet_schedule(&dev->datagram_tasklet);
> +                       vmci_dispatch_dgs(dev);
>                         icr &= ~VMCI_ICR_DATAGRAM;
>                 }
>  
>                 if (icr & VMCI_ICR_NOTIFICATION) {
> -                       tasklet_schedule(&dev->bm_tasklet);
> +                       vmci_process_bitmap(dev);
>                         icr &= ~VMCI_ICR_NOTIFICATION;
>                 }
>  
> @@ -536,7 +531,7 @@ static irqreturn_t vmci_interrupt_bm(int irq, void *_dev)
>         struct vmci_guest_device *dev = _dev;
>  
>         /* For MSI-X we can just assume it was meant for us. */
> -       tasklet_schedule(&dev->bm_tasklet);
> +       vmci_process_bitmap(dev);
>  
>         return IRQ_HANDLED;
>  }
> @@ -638,10 +633,6 @@ static int vmci_guest_probe_device(struct pci_dev *pdev,
>         vmci_dev->iobase = iobase;
>         vmci_dev->mmio_base = mmio_base;
>  
> -       tasklet_init(&vmci_dev->datagram_tasklet,
> -                    vmci_dispatch_dgs, (unsigned long)vmci_dev);
> -       tasklet_init(&vmci_dev->bm_tasklet,
> -                    vmci_process_bitmap, (unsigned long)vmci_dev);
>         init_waitqueue_head(&vmci_dev->inout_wq);
>  
>         if (mmio_base != NULL) {
> @@ -808,8 +799,9 @@ static int vmci_guest_probe_device(struct pci_dev *pdev,
>          * Request IRQ for legacy or MSI interrupts, or for first
>          * MSI-X vector.
>          */
> -       error = request_irq(pci_irq_vector(pdev, 0), vmci_interrupt,
> -                           IRQF_SHARED, KBUILD_MODNAME, vmci_dev);
> +       error = request_threaded_irq(pci_irq_vector(pdev, 0), NULL,
> +                                    vmci_interrupt, IRQF_SHARED,
> +                                    KBUILD_MODNAME, vmci_dev);
>         if (error) {
>                 dev_err(&pdev->dev, "Irq %u in use: %d\n",
>                         pci_irq_vector(pdev, 0), error);
> @@ -823,9 +815,9 @@ static int vmci_guest_probe_device(struct pci_dev *pdev,
>          * between the vectors.
>          */
>         if (vmci_dev->exclusive_vectors) {
> -               error = request_irq(pci_irq_vector(pdev, 1),
> -                                   vmci_interrupt_bm, 0, KBUILD_MODNAME,
> -                                   vmci_dev);
> +               error = request_threaded_irq(pci_irq_vector(pdev, 1), NULL,
> +                                            vmci_interrupt_bm, 0,
> +                                            KBUILD_MODNAME, vmci_dev);
>                 if (error) {
>                         dev_err(&pdev->dev,
>                                 "Failed to allocate irq %u: %d\n",
> @@ -833,9 +825,11 @@ static int vmci_guest_probe_device(struct pci_dev *pdev,
>                         goto err_free_irq;
>                 }
>                 if (caps_in_use & VMCI_CAPS_DMA_DATAGRAM) {
> -                       error = request_irq(pci_irq_vector(pdev, 2),
> -                                           vmci_interrupt_dma_datagram,
> -                                           0, KBUILD_MODNAME, vmci_dev);
> +                       error = request_threaded_irq(pci_irq_vector(pdev, 2),
> +                                                    NULL,
> +                                                   vmci_interrupt_dma_datagram,
> +                                                    0, KBUILD_MODNAME,
> +                                                    vmci_dev);
>                         if (error) {
>                                 dev_err(&pdev->dev,
>                                         "Failed to allocate irq %u: %d\n",
> @@ -871,8 +865,6 @@ static int vmci_guest_probe_device(struct pci_dev *pdev,
>  
>  err_free_irq:
>         free_irq(pci_irq_vector(pdev, 0), vmci_dev);
> -       tasklet_kill(&vmci_dev->datagram_tasklet);
> -       tasklet_kill(&vmci_dev->bm_tasklet);
>  
>  err_disable_msi:
>         pci_free_irq_vectors(pdev);
> @@ -943,9 +935,6 @@ static void vmci_guest_remove_device(struct pci_dev *pdev)
>         free_irq(pci_irq_vector(pdev, 0), vmci_dev);
>         pci_free_irq_vectors(pdev);
>  
> -       tasklet_kill(&vmci_dev->datagram_tasklet);
> -       tasklet_kill(&vmci_dev->bm_tasklet);
> -
>         if (vmci_dev->notification_bitmap) {
>                 /*
>                  * The device reset above cleared the bitmap state of the

I'm happy to see this fixed!

Reviewed-by: Zack Rusin <zackr@xxxxxxxxxx>

z