Nicholas Piggin <npig...@gmail.com> 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 <npig...@gmail.com> > --- > 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: sta...@vger.kernel.org # 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? cheers > diff --git a/arch/powerpc/kernel/entry_64.S b/arch/powerpc/kernel/entry_64.S > index 3320bcac7192..36878b6ee8b8 100644 > --- a/arch/powerpc/kernel/entry_64.S > +++ b/arch/powerpc/kernel/entry_64.S > @@ -911,9 +911,13 @@ END_FTR_SECTION_IFSET(CPU_FTR_HAS_PPR) > beq 1f > rlwinm r7,r7,0,~PACA_IRQ_HARD_DIS > stb r7,PACAIRQHAPPENED(r13) > -1: li r0,0 > - stb r0,PACASOFTIRQEN(r13); > - TRACE_DISABLE_INTS > +1: > +#if defined(CONFIG_TRACE_IRQFLAGS) && defined(CONFIG_BUG) > + /* The interrupt should not have soft enabled. */ > + lbz r7,PACASOFTIRQEN(r13) > +1: tdnei r7,0 > + EMIT_BUG_ENTRY 1b,__FILE__,__LINE__,BUGFLAG_WARNING > +#endif > b .Ldo_restore > > /* > -- > 2.15.0