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); _______________________________________________ iommu mailing list [email protected] https://lists.linuxfoundation.org/mailman/listinfo/iommu
