From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf0-x241.google.com (mail-pf0-x241.google.com [IPv6:2607:f8b0:400e:c00::241]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 3sTjhs0BX7zDsFJ for ; Wed, 7 Sep 2016 22:39:41 +1000 (AEST) Received: by mail-pf0-x241.google.com with SMTP id 128so927673pfb.0 for ; Wed, 07 Sep 2016 05:39:40 -0700 (PDT) Date: Wed, 7 Sep 2016 22:39:21 +1000 From: Nicholas Piggin To: Madhavan Srinivasan Cc: benh@kernel.crashing.org, mpe@ellerman.id.au, anton@samba.org, paulus@samba.org, linuxppc-dev@lists.ozlabs.org Subject: Re: [RFC PATCH v4 11/12] powerpc: Add a Kconfig and a function to set new soft_enabled mask Message-ID: <20160907223921.1a3936df@roar.ozlabs.ibm.com> In-Reply-To: <9fbb7a10-13a2-8542-2050-d73a958167d7@linux.vnet.ibm.com> References: <1472409448-18172-1-git-send-email-maddy@linux.vnet.ibm.com> <1472409448-18172-12-git-send-email-maddy@linux.vnet.ibm.com> <20160829114129.7e68c805@roar.ozlabs.ibm.com> <9fbb7a10-13a2-8542-2050-d73a958167d7@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Mon, 5 Sep 2016 22:48:00 +0530 Madhavan Srinivasan wrote: > On Monday 29 August 2016 07:11 AM, Nicholas Piggin wrote: > > On Mon, 29 Aug 2016 00:07:27 +0530 > > Madhavan Srinivasan wrote: > > > >> New Kconfig is added "CONFIG_IRQ_DEBUG_SUPPORT" to add a warn_on > >> to alert the usage of soft_irq_set_mask() for disabling lower > >> bitmask interrupts. > >> > >> Have also moved the code under the CONFIG_TRACE_IRQFLAGS in > >> arch_local_irq_restore() to new Kconfig as suggested. > >> > >> Patch also adds a new soft_irq_set_mask() to update paca->soft_enabled. > >> > >> Signed-off-by: Madhavan Srinivasan > >> --- > >> arch/powerpc/Kconfig | 4 ++++ > >> arch/powerpc/include/asm/hw_irq.h | 17 +++++++++++++++++ > >> arch/powerpc/kernel/irq.c | 4 ++-- > >> 3 files changed, 23 insertions(+), 2 deletions(-) > >> > >> diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig > >> index 927d2ab2ce08..878f05925340 100644 > >> --- a/arch/powerpc/Kconfig > >> +++ b/arch/powerpc/Kconfig > >> @@ -51,6 +51,10 @@ config TRACE_IRQFLAGS_SUPPORT > >> bool > >> default y > >> > >> +config IRQ_DEBUG_SUPPORT > >> + bool > >> + default n > >> + > >> config LOCKDEP_SUPPORT > >> bool > >> default y > >> diff --git a/arch/powerpc/include/asm/hw_irq.h b/arch/powerpc/include/asm/hw_irq.h > >> index 415734c07cfa..9f71559ce868 100644 > >> --- a/arch/powerpc/include/asm/hw_irq.h > >> +++ b/arch/powerpc/include/asm/hw_irq.h > >> @@ -81,6 +81,23 @@ static inline unsigned long arch_local_irq_disable(void) > >> return flags; > >> } > >> > >> +static inline unsigned long soft_irq_set_mask(int value) > >> +{ > >> + unsigned long flags, zero; > >> + > >> +#ifdef CONFIG_IRQ_DEBUG_SUPPORT > >> + WARN_ON(value <= IRQ_DISABLE_MASK_LINUX); > >> +#endif > >> + asm volatile( > >> + "li %1,%3; lbz %0,%2(13); stb %1,%2(13)" > >> + : "=r" (flags), "=&r" (zero) > >> + : "i" (offsetof(struct paca_struct, soft_enabled)),\ > >> + "i" (value) > >> + : "memory"); > >> + > >> + return flags; > >> +} > > One other thing, if we have: > > > > local_irq_save(flags); // disable LINUX mask -> LINUX > > local_irq_and_pmu_save(flags); // disable PMU mask -> LINUX|PMU > > local_irq_and_pmu_restore(flags); // enable PMU mask -> LINUX > > local_irq_restore(flags); // enable LINUX mask -> NONE > > > > Then the nested code that re-enables PMUs will not replay PMU interrupt > > until the outer irq is re-enabled. I don't *think* this is a problem, > > but it probably should be commented. > > > > Which brings us to arch_local_irq_restore() (from another patch): > > > > > > @@ -208,7 +209,7 @@ notrace void arch_local_irq_restore(unsigned long en) > > > > /* Write the new soft-enabled value */ > > set_soft_enabled(en); > > - if (!en) > > + if (en == IRQ_DISABLE_MASK_LINUX) > > return; > > /* > > * From this point onward, we can take interrupts, preempt, > > > > I think this is a bit buggy for some cases of nested disables. For the > > above it is okay, but if we have: > > > > local_irq_and_pmu_save(flags); > > local_irq_and_pmu_save(flags); > > local_irq_and_pmu_restore(flags); > > local_irq_and_pmu_restore(flags); > > > > > > The first restore will restore LINUX|PMU mask, which will not be caught > > by this check. > > > > Testing instead for non-zero (any IRQ bits masked) should work. We should > > probably also add an IRQ_DEBUG_SUPPORT check to ensure LINUX bit is always > > one of the outer-most bits to be cleared (theoretically we could support > > Just sent out the newer version of the patchset with most of the > comments addressed. Thanks, I'm just having a look through it. > But I am not sure about this comment. IIUC, will something like this > will do? > > diff --git a/arch/powerpc/kernel/irq.c b/arch/powerpc/kernel/irq.c > index a02c6a3bc6fa..af0c08aefbcf 100644 > --- a/arch/powerpc/kernel/irq.c > +++ b/arch/powerpc/kernel/irq.c > @@ -209,6 +209,11 @@ notrace void arch_local_irq_restore(unsigned long en) > unsigned char irq_happened; > unsigned int replay; > > +#ifdef CONFIG_IRQ_DEBUG_SUPPORT > + WARN_ONCE (en & (en & local_paca->soft_enabled), > + "soft_enabled transition to Unsupported state\n"); > +#endif > + > /* Write the new soft-enabled value */ > set_soft_enabled(en); We want to make sure no new bits are set WARN_ON(en & ~local_paca->soft_enabled) My other suggestion was just to ensure the LINUX bit is enabled last: WARN_ON(en & local_paca->soft_enabled & ~IRQ_DISABLE_MASK_LINUX) Thanks, Nick