Due to link order, dma_debug_init is called before debugfs has a chance
to initialize (via debugfs_init which also happens in the core initcall
stage), so the directories for dma-debug are never created.
Move the dma_debug_init initcall from core to postcore stage so that
debugfs will already be initialized by the time this is called, making
it oblivious to link-ordering.
Fixes: 15b28bbcd567 ("dma-debug: move initialization to common code")
Signed-off-by: Anthony Iliopoulos <[email protected]>
---
kernel/dma/debug.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/kernel/dma/debug.c b/kernel/dma/debug.c
index 14de1271463f..49d80ef7f995 100644
--- a/kernel/dma/debug.c
+++ b/kernel/dma/debug.c
@@ -915,7 +915,7 @@ static int dma_debug_init(void)
pr_info("debugging enabled by kernel config\n");
return 0;
}
-core_initcall(dma_debug_init);
+postcore_initcall(dma_debug_init);
static __init int dma_debug_cmdline(char *str)
{
--
2.32.0
On 2021-07-22 10:18, Anthony Iliopoulos wrote:
> Due to link order, dma_debug_init is called before debugfs has a chance
> to initialize (via debugfs_init which also happens in the core initcall
> stage), so the directories for dma-debug are never created.
>
> Move the dma_debug_init initcall from core to postcore stage so that
> debugfs will already be initialized by the time this is called, making
> it oblivious to link-ordering.
Playing initcall chicken here doesn't work so well - the later you
initialise dma-debug itself, the more chance it has to miss early
mappings and raise false positives later. As discussed previously[1] the
better solution would be to decouple the debugfs setup so that just that
part can be deferred until core_initcall_sync or later.
Robin.
[1] https://lore.kernel.org/linux-iommu/YIgGa6yF%[email protected]/
> Fixes: 15b28bbcd567 ("dma-debug: move initialization to common code")
> Signed-off-by: Anthony Iliopoulos <[email protected]>
> ---
> kernel/dma/debug.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/kernel/dma/debug.c b/kernel/dma/debug.c
> index 14de1271463f..49d80ef7f995 100644
> --- a/kernel/dma/debug.c
> +++ b/kernel/dma/debug.c
> @@ -915,7 +915,7 @@ static int dma_debug_init(void)
> pr_info("debugging enabled by kernel config\n");
> return 0;
> }
> -core_initcall(dma_debug_init);
> +postcore_initcall(dma_debug_init);
>
> static __init int dma_debug_cmdline(char *str)
> {
>
On Thu, Jul 22, 2021 at 11:10:24AM +0100, Robin Murphy wrote:
> On 2021-07-22 10:18, Anthony Iliopoulos wrote:
> > Due to link order, dma_debug_init is called before debugfs has a chance
> > to initialize (via debugfs_init which also happens in the core initcall
> > stage), so the directories for dma-debug are never created.
> >
> > Move the dma_debug_init initcall from core to postcore stage so that
> > debugfs will already be initialized by the time this is called, making
> > it oblivious to link-ordering.
>
> Playing initcall chicken here doesn't work so well - the later you
> initialise dma-debug itself, the more chance it has to miss early mappings
> and raise false positives later. As discussed previously[1] the better
> solution would be to decouple the debugfs setup so that just that part can
> be deferred until core_initcall_sync or later.
Thanks for pointing it out, makes sense. What about the following:
From: Anthony Iliopoulos <[email protected]>
Due to link order, dma_debug_init is called before debugfs has a chance
to initialize (via debugfs_init which also happens in the core initcall
stage), so the directories for dma-debug are never created.
Decouple dma_debug_fs_init from dma_debug_init and defer its init until
core_initcall_sync (after debugfs has been initialized) while letting
dma-debug initialization occur as soon as possible to catch any early
mappings, as suggested in [1].
[1] https://lore.kernel.org/linux-iommu/YIgGa6yF%[email protected]/
Fixes: 15b28bbcd567 ("dma-debug: move initialization to common code")
Signed-off-by: Anthony Iliopoulos <[email protected]>
---
kernel/dma/debug.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)
diff --git a/kernel/dma/debug.c b/kernel/dma/debug.c
index 14de1271463f..445754529917 100644
--- a/kernel/dma/debug.c
+++ b/kernel/dma/debug.c
@@ -794,7 +794,7 @@ static int dump_show(struct seq_file *seq, void *v)
}
DEFINE_SHOW_ATTRIBUTE(dump);
-static void dma_debug_fs_init(void)
+static int __init dma_debug_fs_init(void)
{
struct dentry *dentry = debugfs_create_dir("dma-api", NULL);
@@ -807,7 +807,10 @@ static void dma_debug_fs_init(void)
debugfs_create_u32("nr_total_entries", 0444, dentry, &nr_total_entries);
debugfs_create_file("driver_filter", 0644, dentry, NULL, &filter_fops);
debugfs_create_file("dump", 0444, dentry, NULL, &dump_fops);
+
+ return 0;
}
+core_initcall_sync(dma_debug_fs_init);
static int device_dma_allocations(struct device *dev, struct dma_debug_entry **out_entry)
{
@@ -892,8 +895,6 @@ static int dma_debug_init(void)
spin_lock_init(&dma_entry_hash[i].lock);
}
- dma_debug_fs_init();
-
nr_pages = DIV_ROUND_UP(nr_prealloc_entries, DMA_DEBUG_DYNAMIC_ENTRIES);
for (i = 0; i < nr_pages; ++i)
dma_debug_create_entries(GFP_KERNEL);