Nicholas Piggin <[email protected]> writes: > On Mon, 04 Dec 2017 16:09:57 +1100 > Michael Ellerman <[email protected]> wrote: > >> Nicholas Piggin <[email protected]> writes: >> >> > When an interrupt is returning to a soft-disabled context (which can >> > happen for non-maskable interrupts or synchronous interrupts), it goes >> > through the motions of soft-disabling again, including calling >> > TRACE_DISABLE_INTS (i.e., trace_hardirqs_off()). >> > >> > This is not necessary, because we must already be soft-disabled in the >> > interrupt context, it also may be causing crashes in the irq tracing >> > code to re-enter as an nmi. Replace it with a warning to ensure that >> > soft-interrupts are still disabled. >> > >> > Signed-off-by: Nicholas Piggin <[email protected]> >> > --- >> > arch/powerpc/kernel/entry_64.S | 10 +++++++--- >> > 1 file changed, 7 insertions(+), 3 deletions(-) >> >> So this patch is the core of the bug fix I gather. >> >> Git blames says: >> >> Fixes: 7c0482e3d055 ("powerpc/irq: Fix another case of lazy IRQ state >> getting out of sync") >> Cc: [email protected] # v3.4+ >> >> But I'm wondering how this has been broken that long without us >> noticing? You hit it doing some sort of perf stress test I think - so is >> it just that we've never pushed hard enough? Or did something change to >> expose this? Or we're just not sure? > > I'm not really sure. A customer hit it, during either a stress test or > long running workload with lockdep irq tracing and perf running at the > same time. I don't have a lot more details but we might be able to get > some offline if necessary.
No worries. I'll put it in and add it to my maybe-for-stable list. We can let it soak a bit and then send it to stable if we think it's necessary and has no issues. cheers
