On Mon, 16 Aug 2010, David Rientjes wrote: > Ok, so this is panicking because of the error handling when trying to > create sysfs directories with the same name (in this case, :dt-0000064). > I'll look into while this isn't failing gracefully later, but I isolated > this to the new code that statically allocates the DMA caches in > kmem_cache_init_late(). Hmm.... Strange. The DMA caches should create a distinct pattern there. > The iteration runs from 0 to SLUB_PAGE_SHIFT; that's actually incorrect > since the kmem_cache_node cache occupies the first spot in the > kmalloc_caches array and has a size, 64 bytes, equal to a power of two > that is duplicated later. So this patch tries creating two DMA kmalloc > caches with 64 byte object size which triggers a BUG_ON() during > kmem_cache_release() in the error handling later. The kmem_cache_node cache is no longer at position 0. kmalloc_caches[0] should be NULL and therefore be skipped. > The fix is to start the iteration at 1 instead of 0 so that all other > caches have their equivalent DMA caches created and the special-case > kmem_cache_node cache is excluded (see below). > > I'm really curious why nobody else ran into this problem before, > especially if they have CONFIG_SLUB_DEBUG enabled so > struct kmem_cache_node has the same size. Perhaps my early bug report > caused people not to test the series... Which patches were applied? > - the entire iteration in kmem_cache_init_late() needs to be protected by > slub_lock. The comment in create_kmalloc_cache() should be revised > since you're no longer calling it only with irqs disabled. > kmem_cache_init_late() has irqs enabled and, thus, slab_caches must be > protected. I moved it to kmem_cache_init() which is run when we only have one execution thread. That takes care of the issue and ensures that the dma caches are available as early as before. > - a BUG_ON(!name) needs to be added in kmem_cache_init_late() when > kasprintf() returns NULL. This isn't checked in kmem_cache_open() so > it'll only encounter a problem in the sysfs layer. Adding a BUG_ON() > will help track those down. Ok. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>