Messages in this thread Patch in this message | | | Date | Mon, 05 Jul 2021 19:43:53 +0100 | From | Marc Zyngier <> | Subject | Re: [irqchip: irq/irqchip-next] irqdomain: Protect the linear revmap with RCU |
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On Mon, 05 Jul 2021 19:23:27 +0100, Guenter Roeck <linux@roeck-us.net> wrote: > > Hi Marc, > > On 7/5/21 11:01 AM, Marc Zyngier wrote: > > Hi Guenter, > > > > On Mon, 05 Jul 2021 18:23:52 +0100, > > Guenter Roeck <linux@roeck-us.net> wrote: > >> > >> Hi, > >> > >> On Fri, Jun 11, 2021 at 01:54:36PM -0000, irqchip-bot for Marc Zyngier wrote: > >>> The following commit has been merged into the irq/irqchip-next branch of irqchip: > >>> > >>> Commit-ID: d4a45c68dc81f9117ceaff9f058d5fae674181b9 > >>> Gitweb: https://git.kernel.org/pub/scm/linux/kernel/git/maz/arm-platforms/d4a45c68dc81f9117ceaff9f058d5fae674181b9 > >>> Author: Marc Zyngier <maz@kernel.org> > >>> AuthorDate: Mon, 05 Apr 2021 12:57:27 +01:00 > >>> Committer: Marc Zyngier <maz@kernel.org> > >>> CommitterDate: Thu, 10 Jun 2021 13:09:18 +01:00 > >>> > >>> irqdomain: Protect the linear revmap with RCU > >>> > >>> It is pretty odd that the radix tree uses RCU while the linear > >>> portion doesn't, leading to potential surprises for the users, > >>> depending on how the irqdomain has been created. > >>> > >>> Fix this by moving the update of the linear revmap under > >>> the mutex, and the lookup under the RCU read-side lock. > >>> > >>> The mutex name is updated to reflect that it doesn't only > >>> cover the radix-tree anymore. > >>> > >>> Signed-off-by: Marc Zyngier <maz@kernel.org> > >> > >> This patch results in various RCU warnings when booting mipsel images > >> in qemu. I can not revert the patch due to subsequent changes, so I > >> don't know if a simple revert fixes the problem. Log messages and > >> bisect log see below. > > > > Thanks for the heads up. Do you have a config file I can use to > > reproduce this? The QEMU invocation runes would certainly help too. > > > > It strikes me that in drivers/irqchip/irq-mips-cpu.c, > > plat_irq_dispatch() now uses the irqdomain resolution before > > irq_enter() took place. That's certainly a latent bug. I'll fix that > > regardless, but I'd like to make sure this is what you are seeing too. > > > > See http://server.roeck-us.net/qemu/mipsel/ > > config Complete configuration file > defconfig Shortened configuration file > rootfs.cpio root file system (initrd) > run.sh qemu run script (tested with qemu 4.2.1 and 6.0.0) > vmlinux Kernel image experiencing the problem (v5.13-9883-gaf9efb8b661) > > Hope this helps,
It definitely helps, and confirms my hunch. With the patch below, I'm not getting the warnings anymore. I'm pretty sure a number of other MIPS systems suffer from similar issues, which I'll address similarly.
Please let me know if that addresses the issue on your end.
Thanks,
M.
diff --git a/arch/mips/include/asm/irq.h b/arch/mips/include/asm/irq.h index d1477ecb1af9..57561e0e6e8d 100644 --- a/arch/mips/include/asm/irq.h +++ b/arch/mips/include/asm/irq.h @@ -57,6 +57,9 @@ asmlinkage void plat_irq_dispatch(void); extern void do_IRQ(unsigned int irq); +struct irq_domain; +extern void do_domain_IRQ(struct irq_domain *domain, unsigned int irq); + extern void arch_init_irq(void); extern void spurious_interrupt(void); diff --git a/arch/mips/kernel/irq.c b/arch/mips/kernel/irq.c index 85b6c60f285d..c76005cd3b79 100644 --- a/arch/mips/kernel/irq.c +++ b/arch/mips/kernel/irq.c @@ -21,6 +21,7 @@ #include <linux/kallsyms.h> #include <linux/kgdb.h> #include <linux/ftrace.h> +#include <linux/irqdomain.h> #include <linux/atomic.h> #include <linux/uaccess.h> @@ -107,3 +108,16 @@ void __irq_entry do_IRQ(unsigned int irq) irq_exit(); } +void __irq_entry do_domain_IRQ(struct irq_domain *domain, unsigned int hwirq) +{ + struct irq_desc *desc; + + irq_enter(); + check_stack_overflow(); + + desc = irq_resolve_mapping(domain, hwirq); + if (likely(desc)) + handle_irq_desc(desc); + + irq_exit(); +} diff --git a/drivers/irqchip/irq-mips-cpu.c b/drivers/irqchip/irq-mips-cpu.c index 0bbb0b2d0dd5..0c7ae71a0af0 100644 --- a/drivers/irqchip/irq-mips-cpu.c +++ b/drivers/irqchip/irq-mips-cpu.c @@ -127,7 +127,6 @@ static struct irq_chip mips_mt_cpu_irq_controller = { asmlinkage void __weak plat_irq_dispatch(void) { unsigned long pending = read_c0_cause() & read_c0_status() & ST0_IM; - unsigned int virq; int irq; if (!pending) { @@ -137,12 +136,15 @@ asmlinkage void __weak plat_irq_dispatch(void) pending >>= CAUSEB_IP; while (pending) { + struct irq_domain *d; + irq = fls(pending) - 1; if (IS_ENABLED(CONFIG_GENERIC_IRQ_IPI) && irq < 2) - virq = irq_linear_revmap(ipi_domain, irq); + d = ipi_domain; else - virq = irq_linear_revmap(irq_domain, irq); - do_IRQ(virq); + d = irq_domain; + + do_domain_IRQ(d, irq); pending &= ~BIT(irq); } } -- Without deviation from the norm, progress is not possible.
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