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commit f4bfde4d475df0b16c8519aebce818cc663a7108 Author: Zhe Weng <[email protected]> AuthorDate: Wed Nov 5 15:43:04 2025 +0800 drivers/virtio-gpu: Avoid calling free in IRQ Calling `virtio_free_buf` or `kmm_free` inside IRQ may lead to dead lock inside `mm_free`, so we use a free list to store the buffer and reuse it next time. Fortunately, NuttX only uses one async buffer at same time, so we don't need to consider how to free the buffer because we won't have too many in the free list. Signed-off-by: Zhe Weng <[email protected]> --- drivers/virtio/virtio-gpu.c | 125 ++++++++++++++++++++++++++------------------ 1 file changed, 75 insertions(+), 50 deletions(-) diff --git a/drivers/virtio/virtio-gpu.c b/drivers/virtio/virtio-gpu.c index 918a260c83a..9a60e797bab 100644 --- a/drivers/virtio/virtio-gpu.c +++ b/drivers/virtio/virtio-gpu.c @@ -58,24 +58,25 @@ * Private Types ****************************************************************************/ -struct virtio_gpu_priv_s +union virtio_gpu_cmd_u { - struct fb_vtable_s vtable; /* Must be cast compatible with virtio_gpu_priv_s */ - FAR struct virtio_device *vdev; /* Contained virtio device */ - FAR uint8_t *fbmem; /* Allocated framebuffer */ - size_t fblen; /* Size of the framebuffer in bytes */ - fb_coord_t xres; /* Horizontal resolution in pixel columns */ - fb_coord_t yres; /* Vertical resolution in pixel rows */ - fb_coord_t stride; /* Width of a row in bytes */ - uint8_t display; /* Display number */ - spinlock_t lock; /* Lock */ - struct work_s work; /* Work structure for vsync loop */ + FAR union virtio_gpu_cmd_u *next; + struct virtio_gpu_resource_flush flush; }; -struct virtio_gpu_cookie_s +struct virtio_gpu_priv_s { - bool blocking; - FAR void *p; + struct fb_vtable_s vtable; /* Must be cast compatible with virtio_gpu_priv_s */ + FAR struct virtio_device *vdev; /* Contained virtio device */ + FAR union virtio_gpu_cmd_u *freecmd; /* Command data free list */ + FAR uint8_t *fbmem; /* Allocated framebuffer */ + size_t fblen; /* Size of the framebuffer in bytes */ + fb_coord_t xres; /* Horizontal resolution in pixel columns */ + fb_coord_t yres; /* Vertical resolution in pixel rows */ + fb_coord_t stride; /* Width of a row in bytes */ + uint8_t display; /* Display number */ + spinlock_t lock; /* Lock */ + struct work_s work; /* Work structure for vsync loop */ }; struct virtio_gpu_backing_s @@ -145,6 +146,47 @@ static FAR struct virtio_gpu_priv_s *g_virtio_gpu[VIRTIO_GPU_MAX_DISP]; * Private Functions ****************************************************************************/ +/**************************************************************************** + * Name: virtio_gpu_zalloc_cmd + ****************************************************************************/ + +static FAR void *virtio_gpu_zalloc_cmd(FAR struct virtio_gpu_priv_s *priv) +{ + irqstate_t flags = spin_lock_irqsave(&priv->lock); + FAR union virtio_gpu_cmd_u *cmd = priv->freecmd; + if (cmd != NULL) + { + priv->freecmd = cmd->next; + } + + spin_unlock_irqrestore(&priv->lock, flags); + + if (cmd != NULL) + { + memset(cmd, 0, sizeof(*cmd)); + } + else + { + cmd = virtio_zalloc_buf(priv->vdev, sizeof(*cmd), 16); + } + + return cmd; +} + +/**************************************************************************** + * Name: virtio_gpu_free_cmd + ****************************************************************************/ + +static void virtio_gpu_free_cmd(FAR struct virtio_gpu_priv_s *priv, + FAR void *cmd) +{ + FAR union virtio_gpu_cmd_u *node = cmd; + irqstate_t flags = spin_lock_irqsave(&priv->lock); + node->next = priv->freecmd; + priv->freecmd = node; + spin_unlock_irqrestore(&priv->lock, flags); +} + /**************************************************************************** * Name: virtio_gpu_send_cmd * Note: the caller should not touch `buf` after calling this, as it will be @@ -162,14 +204,16 @@ static int virtio_gpu_send_cmd(FAR struct virtqueue *vq, if (writable > 0) { sem_t sem; - struct virtio_gpu_cookie_s cookie; - virtio_free_buf(vq->vq_dev, buf); + if (buf) + { + virtio_gpu_free_cmd(priv, buf); + } + nxsem_init(&sem, 0, 0); - cookie.blocking = true; - cookie.p = &sem; flags = spin_lock_irqsave(&priv->lock); - ret = virtqueue_add_buffer(vq, buf_list, readable, writable, &cookie); + ret = virtqueue_add_buffer(vq, buf_list, readable, writable, + (FAR void *)((uintptr_t)&sem | 0x01)); if (ret >= 0) { virtqueue_kick(vq); @@ -185,36 +229,18 @@ static int virtio_gpu_send_cmd(FAR struct virtqueue *vq, } else { - FAR struct virtio_gpu_cookie_s *cookie; - - cookie = kmm_malloc(sizeof(*cookie)); - if (cookie == NULL) - { - vrterr("ERROR: Failed to allocate cookie memory"); - ret = -ENOMEM; - } - else + flags = spin_lock_irqsave(&priv->lock); + ret = virtqueue_add_buffer(vq, buf_list, readable, writable, buf); + if (ret >= 0) { - cookie->blocking = false; - cookie->p = buf; - flags = spin_lock_irqsave(&priv->lock); - ret = virtqueue_add_buffer(vq, buf_list, readable, writable, - cookie); - if (ret >= 0) - { - virtqueue_kick(vq); - spin_unlock_irqrestore(&priv->lock, flags); - } - else - { - spin_unlock_irqrestore(&priv->lock, flags); - kmm_free(cookie); - } + virtqueue_kick(vq); } + spin_unlock_irqrestore(&priv->lock, flags); + if (buf && ret < 0) { - virtio_free_buf(vq->vq_dev, buf); + virtio_gpu_free_cmd(priv, buf); } } @@ -228,19 +254,18 @@ static int virtio_gpu_send_cmd(FAR struct virtqueue *vq, static void virtio_gpu_done(FAR struct virtqueue *vq) { FAR struct virtio_gpu_priv_s *priv = vq->vq_dev->priv; - FAR struct virtio_gpu_cookie_s *cookie; + FAR void *cookie; while ((cookie = virtqueue_get_buffer_lock(vq, NULL, NULL, &priv->lock)) != NULL) { - if (cookie->blocking) + if ((uintptr_t)cookie & 0x01) { - nxsem_post((FAR sem_t *)cookie->p); + nxsem_post((FAR sem_t *)((uintptr_t)cookie ^ 0x01)); } else { - virtio_free_buf(vq->vq_dev, cookie->p); - kmm_free(cookie); + virtio_gpu_free_cmd(priv, cookie); } } } @@ -483,7 +508,7 @@ static int virtio_gpu_flush_resource(FAR struct virtio_gpu_priv_s *priv, FAR struct virtio_gpu_resource_flush *cmd; struct virtqueue_buf vb; - cmd = virtio_zalloc_buf(priv->vdev, sizeof(*cmd), 16); + cmd = virtio_gpu_zalloc_cmd(priv); if (cmd == NULL) { vrterr("ERROR: Failed to allocate cmd buffer");
