On Mon, Dec 10, 2012 at 09:06:05AM -0500, Steven Rostedt wrote: > On Mon, 2012-12-10 at 13:57 +0000, Russell King - ARM Linux wrote: > > On Mon, Dec 10, 2012 at 08:02:17AM -0500, Steven Rostedt wrote: > > > On Mon, 2012-12-10 at 10:04 +0000, Will Deacon wrote: > > > > Yes, and I think if you do use two 16-bit nops, you can even get rid of > > > > all > > > > the intermediate `sync' operations (I guess you might want one at the > > > > end if > > > > you want the call to become visible at a particular point). > > > > > > Wont work. We are replacing a 32bit call with a nop. That nop must also > > > be 32bits, because we could eventually replace the nop(s) with a 32bit > > > call. > > > > ... which, if it's misaligned to a 32-bit boundary, which can happen with > > Thumb-2 code, will require the replacement to be done atomically; you will > > need to use stop_machine() to ensure that other CPUs don't try to execute > > the instruction mid-way through modification... as I have already > > explained in my previous mails. > > If there's no way to modify a 32bit operation without stop_machine(), > ever with a breakpoint, than we can stop the discussion here. ARM will > forever require stop_machine() for use with tracepoints and ftrace. Too > bad, as ARM was the x86 competitor. Here's something that x86 has a one > up on ARM.
You think that kind of blackmail makes a difference? Look closely at what I've written - I didn't say that there's no way to modify any 32-bit operation without stop_machine(). -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
