On Mon, Oct 2, 2017 at 10:53 PM, frowand.list@gmail.com wrote:
From: Frank Rowand frank.rowand@sony.com
The process of applying an overlay consists of:
- unflatten an overlay FDT (flattened device tree) into an EDT (expanded device tree)
- fixup the phandle values in the overlay EDT to fit in a range above the phandle values in the live device tree
- create the overlay changeset to reflect the contents of the overlay EDT
- apply the overlay changeset, to modify the live device tree, potentially changing the maximum phandle value in the live device tree
There is currently no protection against two overlay applies concurrently determining what range of phandle values are in use in the live device tree, and subsequently changing that range. Add a mutex to prevent multiple overlay applies from occurring simultaneously.
Ignoring 2 checkpatch warnings: Prefer using '"%s...", __func__' so that the WARN() string will be more easily grepped.
Signed-off-by: Frank Rowand frank.rowand@sony.com
drivers/gpu/drm/tilcdc/tilcdc_slave_compat.c | 7 +++++++ drivers/of/overlay.c | 22 ++++++++++++++++++++++ drivers/of/unittest.c | 21 +++++++++++++++++++++ include/linux/of.h | 19 +++++++++++++++++++ 4 files changed, 69 insertions(+)
diff --git a/drivers/gpu/drm/tilcdc/tilcdc_slave_compat.c b/drivers/gpu/drm/tilcdc/tilcdc_slave_compat.c index 7a7be0515bfd..c99f7924b1c6 100644 --- a/drivers/gpu/drm/tilcdc/tilcdc_slave_compat.c +++ b/drivers/gpu/drm/tilcdc/tilcdc_slave_compat.c @@ -221,6 +221,11 @@ static void __init tilcdc_convert_slave_node(void) goto out; }
/** protect from of_resolve_phandles() through of_overlay_apply()*/of_overlay_mutex_lock();
We can't be relying on callers to get the locking right...
overlay = tilcdc_get_overlay(&kft); if (!overlay) goto out;@@ -256,6 +261,8 @@ static void __init tilcdc_convert_slave_node(void) pr_info("%s: ti,tilcdc,slave node successfully converted\n", __func__); out:
of_overlay_mutex_unlock();kfree_table_free(&kft); of_node_put(i2c); of_node_put(slave);diff --git a/drivers/of/overlay.c b/drivers/of/overlay.c index a0d3222febdc..4ed372af6ce7 100644 --- a/drivers/of/overlay.c +++ b/drivers/of/overlay.c @@ -71,6 +71,28 @@ static int build_changeset_next_level(struct overlay_changeset *ovcs, const struct device_node *overlay_node, bool is_symbols_node);
+/*
- of_resolve_phandles() finds the largest phandle in the live tree.
- of_overlay_apply() may add a larger phandle to the live tree.
- Do not allow race between two overlays being applied simultaneously:
- mutex_lock(&of_overlay_phandle_mutex)
- of_resolve_phandles()
- of_overlay_apply()
- mutex_unlock(&of_overlay_phandle_mutex)
Why do these need to be separate functions? I think I mentioned it before, but essentially overlay_data_add() should be part of the overlay API. We may need to allow for callers to do each step, but generally I think the interface should just be "apply this fdt blob".
Rob