+CC Peter, Tglx, Steven On 06/15/2017 01:43 AM, Noam Camus wrote: > From: Noam Camus <noamc at ezchip.com> > > Working with NPS400 we noticed that there is a possibility of L1 > interrupt nesting that may run out kernel stack. > The scenario include serving invoke_softirqs() from irq_exit() > and once local_irq_enable() called can hit another one before we > managed to restore last one and pop some place from kernel stack. > > Serving softirqs at dedicated kernel thread may mitigate this. > We see that many architectures, including x86, behave like this. > > Note 1: All interrupts which must be non threaded > should be marked IRQF_NO_THREAD. > Note 2: using kernel param "threadirqs" is needed to actually > turn this on. This configuration is only a preperation. > > Signed-off-by: Noam Camus <noamc at ezchip.com> > --- > arch/arc/Kconfig | 1 + > 1 files changed, 1 insertions(+), 0 deletions(-) > > diff --git a/arch/arc/Kconfig b/arch/arc/Kconfig > index a545969..f464f97 100644 > --- a/arch/arc/Kconfig > +++ b/arch/arc/Kconfig > @@ -33,6 +33,7 @@ config ARC > select HAVE_OPROFILE > select HAVE_PERF_EVENTS > select HANDLE_DOMAIN_IRQ > + select IRQ_FORCED_THREADING > select IRQ_DOMAIN > select MODULES_USE_ELF_RELA > select NO_BOOTMEM> As Noam notes above and looking at work needed in other arches prior to switching to this: we need mark the low level ints as NO_THREAD. ARC ipi, timer, perf interrupts happen to use request_percpu_irq() which doesn't take flags and doesn't seem to force NO_THREAD internally either. Does that mean we first need to convert all of these sites to __request_percpu_irq(.. NO_THREAD ...) or is there a better way of doing this ! Thx, -Vineet
