On Tue, Jul 24, 2007 at 02:29:05PM -0700, David Brownell wrote: > On at least ARM (and I'm told MIPS too) dma_free_coherent() has a newish > call context requirement: unlike its dma_alloc_coherent() sibling, it > may not be called with IRQs disabled. (This was new behavior on ARM as > of late 2006, caused by ARM SMP updates.)
I think you got the year wrong: 5edf71ae (Russell King 2005-11-25 15:52:51 +0000 364) WARN_ON(irqs_disabled()); which is due to this commit: [ARM] Do not call flush_tlb_kernel_range() with IRQs disabled. We must not call TLB maintainence operations with interrupts disabled, otherwise we risk a lockup in the SMP IPI code. This means that consistent_free() can not be called from a context with IRQs disabled. In addition, we must not hold the lock in consistent_free when we call flush_tlb_kernel_range(). However, we must continue to prevent consistent_alloc() from re-using the memory region until we've finished tearing down the mapping and dealing with the TLB. Therefore, leave the vm_region entry in the list, but mark it inactive before dropping the lock and starting the tear-down process. After the mapping has been torn down, re-acquire the lock and remove the entry from the list. Signed-off-by: Russell King <[EMAIL PROTECTED]> > Since it looks like that restriction won't be removed, this patch changes > the definition of the API to include that requirement. The PCI DMA-mapping API had this restriction. For some reason, this restriction was not carried forward into the DMA-API. Unfortunately the restriction can not be removed without causing the problems described in the commit which introduced it. Or alternatively we scrap ARM SMP entirely, which isn't going to happen. -- Russell King Linux kernel 2.6 ARM Linux - http://www.arm.linux.org.uk/ maintainer of: - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
