Messages in this thread | | | Date | Mon, 5 Oct 2020 09:52:06 +0200 | From | Peter Zijlstra <> | Subject | Re: [WARNING] kernel/rcu/tree.c:1058 rcu_irq_enter+0x15/0x20 |
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On Fri, Oct 02, 2020 at 08:13:13PM +0200, Peter Zijlstra wrote: > > checks within the irq disabling to get rid of the using cpu pointers within > > preemptable code warnings > > Ah, I think I lost a s/__this_cpu_read/raw_cpu_read/ somewhere. The > thing is, if we're preemptible/migratable it will be 0 on both CPUs and > it doesn't matter which 0 we read. If it is !0, IRQs will be disabled > and we can't get migrated.
Aargh, this isn't in fact correct, and that means I have to revert:
fddf9055a60d ("lockdep: Use raw_cpu_*() for per-cpu variables")
The trouble is that on a bunch of architectures we can read the other CPUs variable from the new CPU, long after the old CPU has continued executing things.
So this really needs to be this_cpu_read(). Luckily Sven has already fixed s390, but let me go audit all the other archs.
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