From mboxrd@z Thu Jan 1 00:00:00 1970 From: marc.zyngier@arm.com (Marc Zyngier) Date: Wed, 17 Aug 2016 08:41:23 +0100 Subject: [PATCH] ARM: irq_work: Do not attempt to IPI on non IPI-capable HW In-Reply-To: References: <1471361210-29914-1-git-send-email-marc.zyngier@arm.com> Message-ID: <57B41523.6030202@arm.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On 17/08/16 04:15, Peter Chen wrote: > On Tue, Aug 16, 2016 at 11:26 PM, Marc Zyngier wrote: >> Not all of the ARM HW is IPI capable (i.e. most of the non-SMP >> systems). Unfortunately, some systems do advertise being SMP >> capable, even if they have a single core and do not define >> a cross call method. > > Could you example it? I find all current set_smp_cross_call is defined > under CONFIG_SMP. This doesn't mean that the system will be SMP at runtime (SMP_ON_UP). > Or you will change gic code to define set_smp_cross_call at runtime? No. Also, the GIC is not a universally adopted interrupt controller, as plenty of system don't have one. > >> In this case, irq_work_queue dies >> as arch_irq_work_has_interrupt() fails to detect this >> particular case. >> >> Let's redefine arch_irq_work_has_interrupt() to actually check >> if we're IPI capable instead of simply being SMP. This sidesteps >> the issue entierely. >> >> Signed-off-by: Marc Zyngier >> --- >> arch/arm/include/asm/irq_work.h | 6 +++++- >> arch/arm/include/asm/smp_plat.h | 2 ++ >> arch/arm/kernel/smp.c | 2 +- >> 3 files changed, 8 insertions(+), 2 deletions(-) >> >> diff --git a/arch/arm/include/asm/irq_work.h b/arch/arm/include/asm/irq_work.h >> index 712d03e..3ba3583 100644 >> --- a/arch/arm/include/asm/irq_work.h >> +++ b/arch/arm/include/asm/irq_work.h >> @@ -5,7 +5,11 @@ >> >> static inline bool arch_irq_work_has_interrupt(void) >> { >> - return is_smp(); >> +#ifdef CONFIG_SMP > > Why not using is_smp as condition, it is more strict. > > if (is_smp()) > return !!__smp_cross_call; > else > return false; What's the gain? We're trying to check whether we can actually deliver an IPI. Why should we gate it by finding out whether we're smp_on_up or not? Thanks, M. -- Jazz is not dead. It just smells funny...