Messages in this thread | | | Date | Mon, 25 May 2020 13:25:21 +0200 | From | Peter Zijlstra <> | Subject | Re: Some -serious- BPF-related litmus tests |
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On Fri, May 22, 2020 at 12:38:21PM -0700, Andrii Nakryiko wrote: > On 5/22/20 10:43 AM, Paul E. McKenney wrote: > > On Fri, May 22, 2020 at 10:32:01AM -0400, Alan Stern wrote:
> > > Also, what use is a spinlock that is accessed in only one thread? > > > > Multiple writers synchronize via the spinlock in this case. I am > > guessing that his larger 16-hour test contended this spinlock. > > Yes, spinlock is for coordinating multiple producers. 2p1c cases (bounded > and unbounded) rely on this already. 1p1c cases are sort of subsets (but > very fast to verify) checking only consumer/producer interaction.
Does that spinlock imply that we can now never fix that atrocious bpf_prog_active trainwreck ?
How does that spinlock not trigger the USED <- IN-NMI lockdep check:
f6f48e180404 ("lockdep: Teach lockdep about "USED" <- "IN-NMI" inversions")
?
That is; how can you use a spinlock on the producer side at all?
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