On Tue, Jan 26, 2010 at 08:39:33PM +0100, Manuel Lauss wrote: > DBDMA descriptors need to be located at 32-byte aligned addresses; > however kmalloc in conjunction with the SLAB allocator and > CONFIG_DEBUG_SLUB enabled doesn't deliver any. The dbdma code works > around that by allocating a larger area and realigning the start > address within it. > > When freeing a channel however this adjustment is not taken into > account which results in an oops: > > Kernel bug detected[#1]: > [...] > Call Trace: > [<80186010>] cache_free_debugcheck+0x284/0x318 > [<801869d8>] kfree+0xe8/0x2a0 > [<8010b31c>] au1xxx_dbdma_chan_free+0x2c/0x7c > [<80388dc8>] au1x_pcm_dbdma_free+0x34/0x4c > [<80388fa8>] au1xpsc_pcm_close+0x28/0x38 > [<80383cb8>] soc_codec_close+0x14c/0x1cc > [<8036dbb4>] snd_pcm_release_substream+0x60/0xac > [<8036dc40>] snd_pcm_release+0x40/0xa0 > [<8018c7a8>] __fput+0x11c/0x228 > [<80188f60>] filp_close+0x7c/0x98 > [<80189018>] sys_close+0x9c/0xe4 > [<801022a0>] stack_done+0x20/0x3c > > Fix this by recording the address delivered by kmalloc() and using > it as parameter to kfree(). > > This fix is only necessary with the SLAB allocator and CONFIG_DEBUG_SLAB > enabled; non-debug SLAB, SLUB do return nicely aligned addresses, > debug-enabled SLUB currently panics early in the boot process. Queued for 2.6.34 - should this also go into 2.6.33? Have you considered increasing the value ARCH_KMALLOC_MINALIGN which defaults to 8? Or your own slab cache of suitable alignment? The latter is more something for frequent allocations. Ralf
