drm/i810: remove the BKL

SMP i810 systems were practically nonexistent and the configuration
was not officially supported by Intel at the time when Pentium-III
was common.

With this change, it is still possible to build a distribution kernel
that has support for SMP and includes the i810 driver without the BKL.
As a precaution, check for the theoretical SMP case at run time and
refuse to load the driver.

We also need to disable CONFIG_PREEMPT builds for this driver.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Cc: dri-devel@lists.freedesktop.org
Signed-off-by: Dave Airlie <airlied@redhat.com>

3 files changed, 8 insertions, 20 deletions

diff --git a/drivers/gpu/drm/Kconfig b/drivers/gpu/drm/Kconfig
index 44588764a524..a6feb78c404c 100644
--- a/drivers/gpu/drm/Kconfig
+++ b/drivers/gpu/drm/Kconfig
@@ -73,8 +73,8 @@ source "drivers/gpu/drm/radeon/Kconfig"
 
 config DRM_I810
         tristate "Intel I810"
-        # BKL usage in order to avoid AB-BA deadlocks, may become BROKEN_ON_SMP
-        depends on DRM && AGP && AGP_INTEL && BKL
+        # !PREEMPT because of missing ioctl locking
+        depends on DRM && AGP && AGP_INTEL && (!PREEMPT || BROKEN)
         help
           Choose this option if you have an Intel I810 graphics card.  If M is
           selected, the module will be called i810.  AGP support is required
diff --git a/drivers/gpu/drm/i810/i810_dma.c b/drivers/gpu/drm/i810/i810_dma.c
index ff33e53bbbf8..8f371e8d630f 100644
--- a/drivers/gpu/drm/i810/i810_dma.c
+++ b/drivers/gpu/drm/i810/i810_dma.c
@@ -37,7 +37,6 @@
 #include <linux/interrupt.h>    /* For task queue support */
 #include <linux/delay.h>
 #include <linux/slab.h>
-#include <linux/smp_lock.h>
 #include <linux/pagemap.h>
 
 #define I810_BUF_FREE           2
@@ -94,7 +93,6 @@ static int i810_mmap_buffers(struct file *filp, struct vm_area_struct *vma)
         struct drm_buf *buf;
         drm_i810_buf_priv_t *buf_priv;
 
-        lock_kernel();
         dev = priv->minor->dev;
         dev_priv = dev->dev_private;
         buf = dev_priv->mmap_buffer;
@@ -104,7 +102,6 @@ static int i810_mmap_buffers(struct file *filp, struct vm_area_struct *vma)
         vma->vm_file = filp;
 
         buf_priv->currently_mapped = I810_BUF_MAPPED;
-        unlock_kernel();
 
         if (io_remap_pfn_range(vma, vma->vm_start,
                                vma->vm_pgoff,
@@ -116,7 +113,7 @@ static int i810_mmap_buffers(struct file *filp, struct vm_area_struct *vma)
 static const struct file_operations i810_buffer_fops = {
         .open = drm_open,
         .release = drm_release,
-        .unlocked_ioctl = i810_ioctl,
+        .unlocked_ioctl = drm_ioctl,
         .mmap = i810_mmap_buffers,
         .fasync = drm_fasync,
         .llseek = noop_llseek,
@@ -1242,19 +1239,6 @@ int i810_driver_dma_quiescent(struct drm_device *dev)
         return 0;
 }
 
-/*
- * call the drm_ioctl under the big kernel lock because
- * to lock against the i810_mmap_buffers function.
- */
-long i810_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
-{
-        int ret;
-        lock_kernel();
-        ret = drm_ioctl(file, cmd, arg);
-        unlock_kernel();
-        return ret;
-}
-
 struct drm_ioctl_desc i810_ioctls[] = {
         DRM_IOCTL_DEF_DRV(I810_INIT, i810_dma_init, DRM_AUTH|DRM_MASTER|DRM_ROOT_ONLY|DRM_UNLOCKED),
         DRM_IOCTL_DEF_DRV(I810_VERTEX, i810_dma_vertex, DRM_AUTH|DRM_UNLOCKED),
diff --git a/drivers/gpu/drm/i810/i810_drv.c b/drivers/gpu/drm/i810/i810_drv.c
index 88bcd331e7c5..0152fa27e616 100644
--- a/drivers/gpu/drm/i810/i810_drv.c
+++ b/drivers/gpu/drm/i810/i810_drv.c
@@ -57,7 +57,7 @@ static struct drm_driver driver = {
                  .owner = THIS_MODULE,
                  .open = drm_open,
                  .release = drm_release,
-                 .unlocked_ioctl = i810_ioctl,
+                 .unlocked_ioctl = drm_ioctl,
                  .mmap = drm_mmap,
                  .poll = drm_poll,
                  .fasync = drm_fasync,
@@ -79,6 +79,10 @@ static struct drm_driver driver = {
 
 static int __init i810_init(void)
 {
+        if (num_possible_cpus() > 1) {
+                pr_err("drm/i810 does not support SMP\n");
+                return -EINVAL;
+        }
         driver.num_ioctls = i810_max_ioctl;
         return drm_init(&driver);
 }