On Fri, 25 Aug 2017, Vineet Gupta wrote: > 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. Well, no. x86 supports that, but that does not mean many user add it to the command line. > > 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 > ! PER CPU interrupts are excluded from force threading automatically. Thanks, tglx
