On Tue, Jan 24, 2023 at 05:12:14PM +0000, Mark Rutland wrote: > On Tue, Jan 24, 2023 at 03:44:35PM +0100, Peter Zijlstra wrote: > > On Mon, Jan 23, 2023 at 05:07:53PM -0500, Steven Rostedt wrote: > > > > > Actually, perhaps we can just add this, and all you need to do is create > > > and set CONFIG_NO_RCU_TRACING (or some other name). > > > > Elsewhere I've used CONFIG_ARCH_WANTS_NO_INSTR for this. > > Yes please; if we use CONFIG_ARCH_WANTS_NO_INSTR then arm64 will get this "for > free" once we add the missing checks (which I assume we need) in our ftrace_prepare_return(). Aye. > > Anyway, I took it for a spin and it .... doesn't seems to do the job. > > > > With my patch the first splat is > > > > "RCU not on for: cpuidle_poll_time+0x0/0x70" > > > > While with yours I seems to get the endless: > > > > "WARNING: suspicious RCU usage" > > > > thing. Let me see if I can figure out where it goes side-ways. > > Hmmm... for WARN_ONCE() don't we need to wake RCU first also? I thought we > needed that at least for the printk machinery? Yeah, I'm currently running with a hacked up printk that redirects everything into early_printk() but it still trips up lots. I was just about to go stick on RCU magic into WARN itself, this isn't going to be the only site triggering this fail-cascade.
