On Wed, Jan 27, 2010 at 03:04:58AM -0800, Linus Torvalds wrote:

On Wed, 27 Jan 2010, Peter Zijlstra wrote:

quoted

Right, so there's two aspects:

 1) concurrency when inserting the probe

That's the one I worried about. Stopping all threads will fix it, 
obviously at a disastrous performance cost, but what do I care? As noted, 
there are ways to do it safely with TLB switching, so it's fixable.

That said, inserting a probe is supposed to be a pretty rare
operation, stopping all threads in a process shouldn't be
painful for this aspect.