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Message-ID: <41608ee8-855-ca43-36a0-3544d6b5c9a@inria.fr>
Date: Thu, 28 Aug 2025 14:58:02 +0200 (CEST)
From: Julia Lawall <julia.lawall@...ia.fr>
To: Erick Karanja <karanja99erick@...il.com>
cc: bhelgaas@...gle.com, linux-pci@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH] PCI/VGA: Replace manual locks with lock guards
On Thu, 28 Aug 2025, Erick Karanja wrote:
> Switch from explicit lock/unlock pairs to scoped lock guards.
> This simplifies error handling and improves code readability.
>
> Generated-by: Coccinelle SmPL
>
> Signed-off-by: Erick Karanja <karanja99erick@...il.com>
> ---
> drivers/pci/vgaarb.c | 87 ++++++++++++++++----------------------------
> 1 file changed, 32 insertions(+), 55 deletions(-)
>
> diff --git a/drivers/pci/vgaarb.c b/drivers/pci/vgaarb.c
> index 78748e8d2dba..6a00ee00e362 100644
> --- a/drivers/pci/vgaarb.c
> +++ b/drivers/pci/vgaarb.c
> @@ -501,8 +501,6 @@ EXPORT_SYMBOL(vga_get);
> static int vga_tryget(struct pci_dev *pdev, unsigned int rsrc)
> {
> struct vga_device *vgadev;
> - unsigned long flags;
> - int rc = 0;
>
> vga_check_first_use();
>
> @@ -511,17 +509,13 @@ static int vga_tryget(struct pci_dev *pdev, unsigned int rsrc)
> pdev = vga_default_device();
> if (pdev == NULL)
> return 0;
> - spin_lock_irqsave(&vga_lock, flags);
> + guard(spinlock_irqsave)(&vga_lock);
> vgadev = vgadev_find(pdev);
> - if (vgadev == NULL) {
> - rc = -ENODEV;
> - goto bail;
> - }
> + if (vgadev == NULL)
> + return -ENODEV;
> if (__vga_tryget(vgadev, rsrc))
> - rc = -EBUSY;
> -bail:
> - spin_unlock_irqrestore(&vga_lock, flags);
> - return rc;
> + return -EBUSY;
> + return 0;
> }
>
> /**
> @@ -537,20 +531,17 @@ static int vga_tryget(struct pci_dev *pdev, unsigned int rsrc)
> void vga_put(struct pci_dev *pdev, unsigned int rsrc)
> {
> struct vga_device *vgadev;
> - unsigned long flags;
>
> /* The caller should check for this, but let's be sure */
> if (pdev == NULL)
> pdev = vga_default_device();
> if (pdev == NULL)
> return;
> - spin_lock_irqsave(&vga_lock, flags);
> + guard(spinlock_irqsave)(&vga_lock);
> vgadev = vgadev_find(pdev);
> if (vgadev == NULL)
> - goto bail;
> + return;
> __vga_put(vgadev, rsrc);
> -bail:
> - spin_unlock_irqrestore(&vga_lock, flags);
> }
> EXPORT_SYMBOL(vga_put);
>
> @@ -912,29 +903,20 @@ static void __vga_set_legacy_decoding(struct pci_dev *pdev,
> bool userspace)
> {
> struct vga_device *vgadev;
> - unsigned long flags;
>
> decodes &= VGA_RSRC_LEGACY_MASK;
>
> - spin_lock_irqsave(&vga_lock, flags);
> + guard(spinlock_irqsave)(&vga_lock);
> vgadev = vgadev_find(pdev);
> if (vgadev == NULL)
> - goto bail;
> + return;
>
> /* Don't let userspace futz with kernel driver decodes */
> if (userspace && vgadev->set_decode)
> - goto bail;
> + return;
>
> /* Update the device decodes + counter */
> vga_update_device_decodes(vgadev, decodes);
> -
> - /*
> - * XXX If somebody is going from "doesn't decode" to "decodes"
> - * state here, additional care must be taken as we may have pending
> - * ownership of non-legacy region.
> - */
Maybe the comment should be kept somehow?
julia
> -bail:
> - spin_unlock_irqrestore(&vga_lock, flags);
> }
>
> /**
> @@ -981,14 +963,13 @@ EXPORT_SYMBOL(vga_set_legacy_decoding);
> int vga_client_register(struct pci_dev *pdev,
> unsigned int (*set_decode)(struct pci_dev *pdev, bool decode))
> {
> - unsigned long flags;
> struct vga_device *vgadev;
>
> - spin_lock_irqsave(&vga_lock, flags);
> - vgadev = vgadev_find(pdev);
> - if (vgadev)
> - vgadev->set_decode = set_decode;
> - spin_unlock_irqrestore(&vga_lock, flags);
> + scoped_guard (spinlock_irqsave, &vga_lock) {
> + vgadev = vgadev_find(pdev);
> + if (vgadev)
> + vgadev->set_decode = set_decode;
> + }
> if (!vgadev)
> return -ENODEV;
> return 0;
> @@ -1411,7 +1392,6 @@ static __poll_t vga_arb_fpoll(struct file *file, poll_table *wait)
> static int vga_arb_open(struct inode *inode, struct file *file)
> {
> struct vga_arb_private *priv;
> - unsigned long flags;
>
> pr_debug("%s\n", __func__);
>
> @@ -1421,9 +1401,8 @@ static int vga_arb_open(struct inode *inode, struct file *file)
> spin_lock_init(&priv->lock);
> file->private_data = priv;
>
> - spin_lock_irqsave(&vga_user_lock, flags);
> - list_add(&priv->list, &vga_user_list);
> - spin_unlock_irqrestore(&vga_user_lock, flags);
> + scoped_guard (spinlock_irqsave, &vga_user_lock)
> + list_add(&priv->list, &vga_user_list);
>
> /* Set the client's lists of locks */
> priv->target = vga_default_device(); /* Maybe this is still null! */
> @@ -1438,25 +1417,25 @@ static int vga_arb_release(struct inode *inode, struct file *file)
> {
> struct vga_arb_private *priv = file->private_data;
> struct vga_arb_user_card *uc;
> - unsigned long flags;
> int i;
>
> pr_debug("%s\n", __func__);
>
> - spin_lock_irqsave(&vga_user_lock, flags);
> - list_del(&priv->list);
> - for (i = 0; i < MAX_USER_CARDS; i++) {
> - uc = &priv->cards[i];
> - if (uc->pdev == NULL)
> - continue;
> - vgaarb_dbg(&uc->pdev->dev, "uc->io_cnt == %d, uc->mem_cnt == %d\n",
> - uc->io_cnt, uc->mem_cnt);
> - while (uc->io_cnt--)
> - vga_put(uc->pdev, VGA_RSRC_LEGACY_IO);
> - while (uc->mem_cnt--)
> - vga_put(uc->pdev, VGA_RSRC_LEGACY_MEM);
> + scoped_guard (spinlock_irqsave, &vga_user_lock) {
> + list_del(&priv->list);
> + for (i = 0; i < MAX_USER_CARDS; i++) {
> + uc = &priv->cards[i];
> + if (uc->pdev == NULL)
> + continue;
> + vgaarb_dbg(&uc->pdev->dev,
> + "uc->io_cnt == %d, uc->mem_cnt == %d\n",
> + uc->io_cnt, uc->mem_cnt);
> + while (uc->io_cnt--)
> + vga_put(uc->pdev, VGA_RSRC_LEGACY_IO);
> + while (uc->mem_cnt--)
> + vga_put(uc->pdev, VGA_RSRC_LEGACY_MEM);
> + }
> }
> - spin_unlock_irqrestore(&vga_user_lock, flags);
>
> kfree(priv);
>
> @@ -1470,7 +1449,6 @@ static int vga_arb_release(struct inode *inode, struct file *file)
> static void vga_arbiter_notify_clients(void)
> {
> struct vga_device *vgadev;
> - unsigned long flags;
> unsigned int new_decodes;
> bool new_state;
>
> @@ -1479,7 +1457,7 @@ static void vga_arbiter_notify_clients(void)
>
> new_state = (vga_count > 1) ? false : true;
>
> - spin_lock_irqsave(&vga_lock, flags);
> + guard(spinlock_irqsave)(&vga_lock);
> list_for_each_entry(vgadev, &vga_list, list) {
> if (vgadev->set_decode) {
> new_decodes = vgadev->set_decode(vgadev->pdev,
> @@ -1487,7 +1465,6 @@ static void vga_arbiter_notify_clients(void)
> vga_update_device_decodes(vgadev, new_decodes);
> }
> }
> - spin_unlock_irqrestore(&vga_lock, flags);
> }
>
> static int pci_notify(struct notifier_block *nb, unsigned long action,
> --
> 2.43.0
>
>
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