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Date: Sat, 21 Jun 2008 15:42:56 -0400 (EDT)
From: Mikulas Patocka <mpatocka@...hat.com>
To: David Miller <davem@...emloft.net>
cc: sparclinux@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: stack overflow on Sparc64
On Fri, 20 Jun 2008, David Miller wrote:
> From: David Miller <davem@...emloft.net>
> Date: Fri, 20 Jun 2008 14:41:28 -0700 (PDT)
>
>> Next week I'll make one of my primary projects the implementation of
>> IRQ stacks for sparc64.
>
> Next week came real fast :-)
>
> Amazingly this patch worked the first time I booted it up on my
> dual-cpu workstation (using SMP + PREEMPT). I'm worried that maybe
> gcc can do some clever things and not allow my extremely simple
> approach to work, but anyways it might work for you and it's worth
> giving a try.
>
> sparc64: Implement support for IRQ stacks.
For me it doesn't work. Locked up after "console: colour dummy device
80x25".
Mikulas
> Signed-off-by: David S. Miller <davem@...emloft.net>
>
> diff --git a/arch/sparc64/Kconfig.debug b/arch/sparc64/Kconfig.debug
> index 6a4d28a..df80962 100644
> --- a/arch/sparc64/Kconfig.debug
> +++ b/arch/sparc64/Kconfig.debug
> @@ -41,4 +41,11 @@ config FRAME_POINTER
> depends on MCOUNT
> default y
>
> +config IRQSTACKS
> + bool "Use separate kernel stacks when processing interrupts"
> + help
> + If you say Y here the kernel will use separate kernel stacks
> + for handling hard and soft interrupts. This can help avoid
> + overflowing the process kernel stacks.
> +
> endmenu
> diff --git a/arch/sparc64/kernel/irq.c b/arch/sparc64/kernel/irq.c
> index b441a26..24820fa 100644
> --- a/arch/sparc64/kernel/irq.c
> +++ b/arch/sparc64/kernel/irq.c
> @@ -674,10 +674,42 @@ void ack_bad_irq(unsigned int virt_irq)
> ino, virt_irq);
> }
>
> +#ifdef CONFIG_IRQSTACKS
> +void *hardirq_stack[NR_CPUS];
> +void *softirq_stack[NR_CPUS];
> +
> +static void *set_hardirq_stack(void)
> +{
> + void *orig_sp, *sp = hardirq_stack[smp_processor_id()];
> +
> + __asm__ __volatile__("mov %%sp, %0" : "=r" (orig_sp));
> + if (orig_sp < sp ||
> + orig_sp > (sp + THREAD_SIZE)) {
> + sp += THREAD_SIZE - 192 - STACK_BIAS;
> + __asm__ __volatile__("mov %0, %%sp" : : "r" (sp));
> + }
> +
> + return orig_sp;
> +}
> +static void restore_hardirq_stack(void *orig_sp)
> +{
> + __asm__ __volatile__("mov %0, %%sp" : : "r" (orig_sp));
> +}
> +#else
> +static void *set_hardirq_stack(void)
> +{
> + return NULL;
> +}
> +static void restore_hardirq_stack(void *orig_sp)
> +{
> +}
> +#endif
> +
> void handler_irq(int irq, struct pt_regs *regs)
> {
> unsigned long pstate, bucket_pa;
> struct pt_regs *old_regs;
> + void *orig_sp;
>
> clear_softint(1 << irq);
>
> @@ -695,6 +727,8 @@ void handler_irq(int irq, struct pt_regs *regs)
> "i" (PSTATE_IE)
> : "memory");
>
> + orig_sp = set_hardirq_stack();
> +
> while (bucket_pa) {
> struct irq_desc *desc;
> unsigned long next_pa;
> @@ -711,10 +745,40 @@ void handler_irq(int irq, struct pt_regs *regs)
> bucket_pa = next_pa;
> }
>
> + restore_hardirq_stack(orig_sp);
> +
> irq_exit();
> set_irq_regs(old_regs);
> }
>
> +#ifdef CONFIG_IRQSTACKS
> +void do_softirq(void)
> +{
> + unsigned long flags;
> +
> + if (in_interrupt())
> + return;
> +
> + local_irq_save(flags);
> +
> + if (local_softirq_pending()) {
> + void *orig_sp, *sp = softirq_stack[smp_processor_id()];
> +
> + sp += THREAD_SIZE - 192 - STACK_BIAS;
> +
> + __asm__ __volatile__("mov %%sp, %0\n\t"
> + "mov %1, %%sp"
> + : "=&r" (orig_sp)
> + : "r" (sp));
> + __do_softirq();
> + __asm__ __volatile__("mov %0, %%sp"
> + : : "r" (orig_sp));
> + }
> +
> + local_irq_restore(flags);
> +}
> +#endif
> +
> #ifdef CONFIG_HOTPLUG_CPU
> void fixup_irqs(void)
> {
> diff --git a/arch/sparc64/mm/init.c b/arch/sparc64/mm/init.c
> index 84898c4..56e22f4 100644
> --- a/arch/sparc64/mm/init.c
> +++ b/arch/sparc64/mm/init.c
> @@ -49,6 +49,7 @@
> #include <asm/sstate.h>
> #include <asm/mdesc.h>
> #include <asm/cpudata.h>
> +#include <asm/irq.h>
>
> #define MAX_PHYS_ADDRESS (1UL << 42UL)
> #define KPTE_BITMAP_CHUNK_SZ (256UL * 1024UL * 1024UL)
> @@ -1817,6 +1818,18 @@ void __init paging_init(void)
> if (tlb_type == hypervisor)
> sun4v_mdesc_init();
>
> +#ifdef CONFIG_IRQSTACKS
> + /* Once the OF device tree and MDESC have been setup, we know
> + * the list of possible cpus. Therefore we can allocate the
> + * IRQ stacks.
> + */
> + for_each_possible_cpu(i) {
> + /* XXX Use node local allocations... XXX */
> + softirq_stack[i] = __va(lmb_alloc(THREAD_SIZE, THREAD_SIZE));
> + hardirq_stack[i] = __va(lmb_alloc(THREAD_SIZE, THREAD_SIZE));
> + }
> +#endif
> +
> /* Setup bootmem... */
> last_valid_pfn = end_pfn = bootmem_init(phys_base);
>
> diff --git a/include/asm-sparc64/irq.h b/include/asm-sparc64/irq.h
> index 0bb9bf5..d71b5ff 100644
> --- a/include/asm-sparc64/irq.h
> +++ b/include/asm-sparc64/irq.h
> @@ -90,4 +90,10 @@ static inline unsigned long get_softint(void)
> return retval;
> }
>
> +#ifdef CONFIG_IRQSTACKS
> +extern void *hardirq_stack[NR_CPUS];
> +extern void *softirq_stack[NR_CPUS];
> +#define __ARCH_HAS_DO_SOFTIRQ
> +#endif
> +
> #endif
>
--
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