On Wed, Jun 28, 2017 at 01:14:04PM -0700, Andi Kleen wrote: > It can be a useful debugging tool for a specific class of bugs: > when kernel software is looping forever. > > But if that happens does it really matter how many iterations the > loop does before it is stopped? > > Even the current timeout is essentially eternity in CPU time, and 3x > eternity is still eternity. That isn't true. We have customers that test the accuracy and file bugs. I had to write a RHEL whitepaper a number of years ago explaining why the softlockup took 62 seconds to fire instead of 60. Customers were changing the watchdog_thresh when the system slowed down to purposely trigger a panic (which exposed race conditions leading Uli to redesign the sysctl interface). I don't feel like explaining to our customers how we regressed on our watchdog accuracy. It is exhausting, especially if it is a debug feature. > > > The hrtimer increase maintains that and just adds a few more > > interrupts/second. > > Interruptions are a big deal for many people. Yes, and we probably have customers that will complain on that too. Either solution is a lose/lose. And yes, we will probably get bit by the false NMI problems on those Intel boxes. This is why I was preferring a real solution. The question is, if the real solution is going to take a while, what is the least sucky solution for now? Or how do we minimize it to a specific class of Intel boxes. Cheers, Don