The previous code was not thread safe and caused undefined behavior from spurious duplicate resource IDs. In this patch, an atomic_t is used instead. We no longer see any duplicate IDs in tests with this change.
Signed-off-by: John Bates jbates@chromium.org ---
drivers/gpu/drm/virtio/virtgpu_object.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/drivers/gpu/drm/virtio/virtgpu_object.c b/drivers/gpu/drm/virtio/virtgpu_object.c index 017a9e0fc3bb..b11c1fce1770 100644 --- a/drivers/gpu/drm/virtio/virtgpu_object.c +++ b/drivers/gpu/drm/virtio/virtgpu_object.c @@ -42,8 +42,8 @@ static int virtio_gpu_resource_id_get(struct virtio_gpu_device *vgdev, * "f91a9dd35715 Fix unlinking resources from hash * table." (Feb 2019) fixes the bug. */ - static int handle; - handle++; + static atomic_t seqno; + int handle = atomic_inc_return(&seqno); *resid = handle + 1; } else { int handle = ida_alloc(&vgdev->resource_ida, GFP_KERNEL);
On Wed, Feb 19, 2020 at 12:40 PM John Bates jbates@chromium.org wrote:
The previous code was not thread safe and caused undefined behavior from spurious duplicate resource IDs. In this patch, an atomic_t is used instead. We no longer see any duplicate IDs in tests with this change.
Signed-off-by: John Bates jbates@chromium.org
drivers/gpu/drm/virtio/virtgpu_object.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/drivers/gpu/drm/virtio/virtgpu_object.c b/drivers/gpu/drm/virtio/virtgpu_object.c index 017a9e0fc3bb..b11c1fce1770 100644 --- a/drivers/gpu/drm/virtio/virtgpu_object.c +++ b/drivers/gpu/drm/virtio/virtgpu_object.c @@ -42,8 +42,8 @@ static int virtio_gpu_resource_id_get(struct virtio_gpu_device *vgdev, * "f91a9dd35715 Fix unlinking resources from hash * table." (Feb 2019) fixes the bug. */
static int handle;handle++;
static atomic_t seqno;int handle = atomic_inc_return(&seqno); *resid = handle + 1; } else { int handle = ida_alloc(&vgdev->resource_ida, GFP_KERNEL);-- 2.25.0.265.gbab2e86ba0-goog
On Wed, Feb 19, 2020 at 4:20 PM John Bates jbates@google.com wrote:
On Wed, Feb 19, 2020 at 12:40 PM John Bates jbates@chromium.org wrote:
The previous code was not thread safe and caused undefined behavior from spurious duplicate resource IDs. In this patch, an atomic_t is used instead. We no longer see any duplicate IDs in tests with this change.
Signed-off-by: John Bates jbates@chromium.org
drivers/gpu/drm/virtio/virtgpu_object.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/drivers/gpu/drm/virtio/virtgpu_object.c b/drivers/gpu/drm/virtio/virtgpu_object.c index 017a9e0fc3bb..b11c1fce1770 100644 --- a/drivers/gpu/drm/virtio/virtgpu_object.c +++ b/drivers/gpu/drm/virtio/virtgpu_object.c @@ -42,8 +42,8 @@ static int virtio_gpu_resource_id_get(struct virtio_gpu_device *vgdev, * "f91a9dd35715 Fix unlinking resources from hash * table." (Feb 2019) fixes the bug. */
static int handle;handle++;
static atomic_t seqno;
nit: ATOMIC_INIT(0)?
int handle = atomic_inc_return(&seqno); *resid = handle + 1; } else { int handle = ida_alloc(&vgdev->resource_ida, GFP_KERNEL);-- 2.25.0.265.gbab2e86ba0-goog
Hi John,
On Thu, 20 Feb 2020 at 08:45, John Bates jbates@chromium.org wrote:
The previous code was not thread safe and caused undefined behavior from spurious duplicate resource IDs. In this patch, an atomic_t is used instead. We no longer see any duplicate IDs in tests with this change.
Signed-off-by: John Bates jbates@chromium.org
Adding a fixes tag like below makes it easier to track. Especially for Greg and team who are working on stable kernels.
Fixes: 3e93bc2a58aa ("drm/virtio: make resource id workaround runtime switchable.")
HTH Emil
On Thu, Feb 20, 2020 at 5:30 AM Emil Velikov emil.l.velikov@gmail.com wrote:
Hi John,
On Thu, 20 Feb 2020 at 08:45, John Bates jbates@chromium.org wrote:
The previous code was not thread safe and caused undefined behavior from spurious duplicate resource IDs. In this patch, an atomic_t is used instead. We no longer see any duplicate IDs in tests with this change.
Signed-off-by: John Bates jbates@chromium.org
Adding a fixes tag like below makes it easier to track. Especially for Greg and team who are working on stable kernels.
Fixes: 3e93bc2a58aa ("drm/virtio: make resource id workaround runtime switchable.")
FWIW, the fixes tag should refer to this commit instead
commit 16065fcdd19ddb9e093192914ac863884f308766 Author: Gerd Hoffmann kraxel@redhat.com Date: Fri Feb 8 15:04:09 2019 +0100
drm/virtio: do NOT reuse resource ids
HTH Emil _______________________________________________ dri-devel mailing list dri-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/dri-devel
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