Date: Sun, 9 Jan 2005 12:11:32 +1100 From: Peter Jeremy <PeterJeremy@optushome.com.au> To: freebsd-current@freebsd.org Subject: bus_dmamem_alloc() can't handle large NOWAIT requests Message-ID: <20050109011132.GJ39552@cirb503493.alcatel.com.au>
next in thread | raw e-mail | index | archive | help
I've just been tracking down a panic in 4.x and found that the problem is still present in 6.x. According to bus_dma(9), bus_dmamem_alloc() can be invoked with a flag BUS_DMA_NOWAIT to indicate that sleep()ing is not allowed. At least on the i386, if the requested size exceeds 1 page (or some other cases), the requested memory will be allocated via contigmalloc(). bus_dmamem_alloc() maps BUS_DMA_NOWAIT to M_NOWAIT but contigmalloc() does not support M_NOWAIT and will tsleep() under some conditions. Unfortunately, I don't know enough about the VM code to be able to suggest a fix. -- Peter Jeremy
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?20050109011132.GJ39552>