Messages in this thread | | | Date | Tue, 1 Dec 2020 08:53:21 -0800 | From | "Paul E. McKenney" <> | Subject | Re: [GIT pull] locking/urgent for v5.10-rc6 |
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On Tue, Dec 01, 2020 at 03:55:19PM +0100, Peter Zijlstra wrote: > On Tue, Dec 01, 2020 at 06:46:44AM -0800, Paul E. McKenney wrote: > > > > So after having talked to Sven a bit, the thing that is happening, is > > > that this is the one place where we take interrupts with RCU being > > > disabled. Normally RCU is watching and all is well, except during idle. > > > > Isn't interrupt entry supposed to invoke rcu_irq_enter() at some point? > > Or did this fall victim to recent optimizations? > > It does, but the problem is that s390 is still using > trace_hardirqs_off(), which calls into tracing before RCU is enabled. > > The entry order between lockdep, rcu and tracing is critical. > > You can't call into tracing without RCU running, > you can't call into RCU without lockdep setup, > you can't call the (old) lockdep setup without landing in tracing.
Whew! ;-)
Thanx, Paul
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