On Thu, Jan 24, 2019 at 06:29:55PM -0800, Eric Dumazet wrote: > > > On 01/24/2019 03:58 PM, Alexei Starovoitov wrote: > > On Thu, Jan 24, 2019 at 07:01:09PM +0100, Peter Zijlstra wrote: > > >> and from NMI ... > > > > progs are not preemptable and map syscall accessors have bpf_prog_active > > counters. > > So nmi/kprobe progs will not be running when syscall is running. > > Hence dead lock is not possible and irq_save is not needed. > > > Speaking of NMI, how pcpu_freelist_push() and pop() can actually work ? > > It seems bpf_get_stackid() can be called from NMI, and lockdep seems to > complain loudly
it's a known false positive. https://lkml.org/lkml/2018/7/25/756 and the same answer as before: we're not going to penalize performance to shut up false positive.
