On Mon, Feb 10, 2014 at 03:12:47PM +0000, Dave Martin wrote: > Firstly, blindly adding 4 to PC is obviouly not right, partly because we > might be running an unrelated thread by the time the abort fires, and > also because the affected instruction might not be 4 bytes in size in a > Thumb kernel.
Exactly. We ended up on some platforms having special accessors for PCI where we included a number of 'mov r0, r0' instructions after the accessor so we could properly cope with them - but this required knowledge that we were going to only receive an imprecise abort from these accessors and only for a few cycles after the instruction. However, that's not true with modern architectures. The point they're received will _not_ be the load/store which resulted in the abort, and in the case of a write, they could be many hundreds of cycles later, especially if the write has been buffered. So adding four to the PC is definitely a very /bad/ thing to do. -- FTTC broadband for 0.8mile line: 5.8Mbps down 500kbps up. Estimation in database were 13.1 to 19Mbit for a good line, about 7.5+ for a bad. Estimate before purchase was "up to 13.2Mbit". -- 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/
