* Kyle Huey <me@xxxxxxxxxxxx> wrote: > On Wed, Jul 5, 2017 at 10:07 PM, Robert O'Callahan <robert@xxxxxxxxxxxxx> wrote: > > On Tue, Jul 4, 2017 at 3:21 AM, Mark Rutland <mark.rutland@xxxxxxx> wrote: > >> Should any of those be moved into the "should be dropped" pile? > > > > Why not be conservative and clear every sample you're not sure about? > > > > We'd appreciate a fix sooner rather than later here, since rr is > > currently broken on every stable Linux kernel and our attempts to > > implement a workaround have failed. > > > > (We have separate "interrupt" and "measure" counters, and I thought we > > might work around this regression by programming the "interrupt" > > counter to count kernel events as well as user events (interrupting > > early is OK), but that caused our (completely separate) "measure" > > counter to report off-by-one results (!), which seems to be a > > different bug present on a range of older kernels.) > > This seems to have stalled out here unfortunately. > > Can we get a consensus (from ingo or peterz?) on Mark's question? Or, > alternatively, can we move the patch at the top of this thread forward > on the stable branches until we do reach an answer to that question? > > We've abandoned hope of working around this problem in rr and are > currently broken for all of our users with an up-to-date kernel, so > the situation for us is rather dire at the moment I'm afraid. Sorry about that - I've queued up a revert for the original commit and will send the fix to Linus later today. I've added a -stable tag as well so it can be forwarded to Greg the moment it hits upstream. We should do the original fix as well, but in a version that does not skip the sample but zeroes out the RIP and registers (or sets them all to -1LL) - and also covers other possible places where skid-RIP is exposed, such as LBR. Thanks, Ingo