From mboxrd@z Thu Jan 1 00:00:00 1970 From: Helge Deller Subject: Re: [PATCH] parisc: increase kernel stack size to 32k Date: Sat, 27 Apr 2013 23:53:43 +0200 Message-ID: <517C48E7.7050701@gmx.de> References: <20130423202203.GA7287@p100.box> <51778ADE.4010906@gmx.de> <1366836075.1971.22.camel@dabdike> <20130426223014.GA19671@p100.box> Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="------------000209020801060300070501" Cc: linux-parisc@vger.kernel.org, John David Anglin To: James Bottomley Return-path: In-Reply-To: <20130426223014.GA19671@p100.box> List-ID: List-Id: linux-parisc.vger.kernel.org This is a multi-part message in MIME format. --------------000209020801060300070501 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit On 04/27/2013 12:30 AM, Helge Deller wrote: > * James Bottomley : >> On Wed, 2013-04-24 at 09:33 +0200, Helge Deller wrote: >>> On 04/23/2013 10:22 PM, Helge Deller wrote: >>>> commit e4e1e78facf7565cada909a69c7fb6415b6e7b83 >>>> Author: Helge Deller >>>> Date: Tue Apr 23 17:19:37 2013 +0200 >>>> >>>> parisc: increase kernel stack size to 32k >>>> >>>> --- a/arch/parisc/include/asm/thread_info.h >>>> +++ b/arch/parisc/include/asm/thread_info.h >>>> -#define THREAD_SIZE_ORDER 2 >>>> +#define THREAD_SIZE_ORDER 3 /* 32k stack */ >>> >>> I tested again, and it actually needs to be 64k stacks to not crash any longer. >>> So, the right temporary fix is: >>> >>>> +#define THREAD_SIZE_ORDER 4 /* 64k stack */ >>> >>> Will send updated patch soon. >> >> This is an indicator of something seriously wrong somewhere. We've >> always had the 16k stack just because of our large frames. In theory, >> the IRQ stack should only be the same size as the kernel stack, so if we >> have both in the same place, we should only need at max 32k ... if we're >> still seeing problems related to stack overrun, then it might be we have >> an IRQ recursion where we shouldn't have. To be honest, I have a hard >> time explaining why our stacks should be over 8k. Attached is a new version of my irq-stack-patch, which made my system really stable :-) As test I did used "hackbench 300" (from the LTP project) which created 12000 threads: uptime: 23:44:09 up 17 min, 2 users, load average: 1232.23, 2966.09, 2466.39 My findings so far: * kernel stack: THREAD_SIZE_ORDER needs to be at least 2 (=16k). x86 has 1 (8k). With 8k kernel stacks and DEBUG_STACKOVERFLOW enabled, I get directly after bootup: stackcheck: swapper/0 has overflown a kernel stack (sp:bfc52030, stk bottom-top:bfc50000-bfc52000) * IRQ stack: 16k seems sufficient as well. So, the combination of 16k kernel stack and 16k irq stacks seems OK. I still need to clean up my patch, test if backtraces still work (with which I currently have problems) and prepare a final patch. Helge --------------000209020801060300070501 Content-Type: text/plain; charset=UTF-8; name="irqstack.patch6" Content-Transfer-Encoding: 7bit Content-Disposition: attachment; filename="irqstack.patch6" diff --git a/arch/parisc/Kconfig.debug b/arch/parisc/Kconfig.debug index 7305ac8..ed88c37 100644 --- a/arch/parisc/Kconfig.debug +++ b/arch/parisc/Kconfig.debug @@ -12,6 +12,17 @@ config DEBUG_RODATA portion of the kernel code won't be covered by a TLB anymore. If in doubt, say "N". +config DEBUG_STACKOVERFLOW + bool "Check for stack overflows" + depends on DEBUG_KERNEL + ---help--- + Say Y here if you want to check the overflows of kernel, IRQ + and exception stacks. This option will cause messages of the + stacks in detail when free stack space drops below a certain + limit. + If in doubt, say "N". + + config DEBUG_STRICT_USER_COPY_CHECKS bool "Strict copy size checks" depends on DEBUG_KERNEL && !TRACE_BRANCH_PROFILING diff --git a/arch/parisc/include/asm/irq.h b/arch/parisc/include/asm/irq.h index 1073599..0417ebf 100644 --- a/arch/parisc/include/asm/irq.h +++ b/arch/parisc/include/asm/irq.h @@ -10,6 +10,8 @@ #include #include +#define __ARCH_HAS_DO_SOFTIRQ + #define NO_IRQ (-1) #ifdef CONFIG_GSC diff --git a/arch/parisc/include/asm/processor.h b/arch/parisc/include/asm/processor.h index 09b54a5..d725591 100644 --- a/arch/parisc/include/asm/processor.h +++ b/arch/parisc/include/asm/processor.h @@ -20,8 +20,6 @@ #endif /* __ASSEMBLY__ */ -#define KERNEL_STACK_SIZE (4*PAGE_SIZE) - /* * Default implementation of macro that returns current * instruction pointer ("program counter"). @@ -33,6 +31,8 @@ #endif #define current_text_addr() ({ void *pc; current_ia(pc); pc; }) +#define get_current_sp(sp) __asm__("copy %%r30, %0" : "=r"(sp)) + #define TASK_SIZE_OF(tsk) ((tsk)->thread.task_size) #define TASK_SIZE TASK_SIZE_OF(current) #define TASK_UNMAPPED_BASE (current->thread.map_base) @@ -61,6 +61,20 @@ #ifndef __ASSEMBLY__ /* + * IRQ STACK - used for irq and irq bh handler + */ +#ifdef __KERNEL__ + +#define IRQ_STACK_SIZE (4096 << 2) /* = 16k, todo: use: PAGE_SIZE instead of 4096 */ + +union irq_stack_union { + unsigned long irq_stack[IRQ_STACK_SIZE/sizeof(unsigned long)]; +}; + +DECLARE_PER_CPU(union irq_stack_union, irq_stack_union); +#endif /* __KERNEL__ */ + +/* * Data detected about CPUs at boot time which is the same for all CPU's. * HP boxes are SMP - ie identical processors. * diff --git a/arch/parisc/include/asm/thread_info.h b/arch/parisc/include/asm/thread_info.h index d1fb79a..85568cc 100644 --- a/arch/parisc/include/asm/thread_info.h +++ b/arch/parisc/include/asm/thread_info.h @@ -40,7 +40,7 @@ struct thread_info { /* thread information allocation */ -#define THREAD_SIZE_ORDER 2 +#define THREAD_SIZE_ORDER 2 /* keep value 2 for 16k, use 3 for 32k */ /* Be sure to hunt all references to this down when you change the size of * the kernel stack */ #define THREAD_SIZE (PAGE_SIZE << THREAD_SIZE_ORDER) diff --git a/arch/parisc/kernel/entry.S b/arch/parisc/kernel/entry.S index f33201b..117d516 100644 --- a/arch/parisc/kernel/entry.S +++ b/arch/parisc/kernel/entry.S @@ -1997,6 +1997,28 @@ ftrace_stub: ENDPROC(return_to_handler) #endif /* CONFIG_FUNCTION_TRACER */ +/* void call_on_stack(unsigned long param1, void *func, unsigned long new_stack) */ +ENTRY(call_on_stack) + STREG %sp, 8(%arg2) + STREG %rp, 16(%arg2) + + /* HPPA calling convention for function pointers */ +#ifdef CONFIG_64BIT + LDREG 16(%arg1), %arg1 + bve,l (%arg1), %rp + addi 0x40, %arg2, %sp +#else + addi 0x40, %arg2, %sp + be,l 0(%sr4,%arg1), %sr0, %r31 + copy %r31, %rp +#endif + + addi -0x40, %sp, %sp + LDREG 16(%sp),%rp + bv (%rp) + LDREG 8(%sp),%sp +ENDPROC(call_on_stack) + get_register: /* diff --git a/arch/parisc/kernel/irq.c b/arch/parisc/kernel/irq.c index 8094d3e..6c23120 100644 --- a/arch/parisc/kernel/irq.c +++ b/arch/parisc/kernel/irq.c @@ -330,6 +330,60 @@ static inline int eirr_to_irq(unsigned long eirr) return (BITS_PER_LONG - bit) + TIMER_IRQ; } + +int sysctl_panic_on_stackoverflow __read_mostly; + +/* + * Stack overflow check: + */ +static inline void stack_overflow_check(unsigned long sp, unsigned long stack_start, + unsigned long stack_size, const char *stackname) +{ +#ifdef CONFIG_DEBUG_STACKOVERFLOW +#define STACK_MARGIN 128 + if (likely((sp - stack_start) < (stack_size - STACK_MARGIN))) + return; + + WARN("stackcheck: %s has overflown the %s stack (sp:%lx, stk bottom-top:%lx-%lx)\n", + current->comm, stackname, sp, + stack_start, stack_start + stack_size); + + if (sysctl_panic_on_stackoverflow) + panic("low stack detected by irq handler - check messages\n"); +#endif +} + +extern void call_on_stack(unsigned long param1, void *func, unsigned long new_stack); /* in entry.S */ + + +static void noinline execute_on_irq_stack(void *func, unsigned long param1) +{ + int cpu = smp_processor_id(); + unsigned long sp, irq_stack; + void (*direct_call)(unsigned long param1) = func; + + irq_stack = (unsigned long) &per_cpu(irq_stack_union, cpu); + get_current_sp(sp); + + /* + * this is where we try to switch to the IRQ stack. However, if we are + * already using the IRQ stack (because we interrupted a hardirq + * handler) we can't do that and just have to keep using the + * current stack (which is the irq stack already after all) + */ + + if ((sp - irq_stack) >= IRQ_STACK_SIZE) { + stack_overflow_check(sp, (unsigned long)task_stack_page(current), THREAD_SIZE, "kernel"); + call_on_stack(param1, func, irq_stack); + // WARN_ON_ONCE(1); /* enable to check if irq stack is being used. */ + // TODO: check if backtrace works from irq stack + // TODO: use get_current_sp() macro in other code as well. + } else { + stack_overflow_check(sp, irq_stack, IRQ_STACK_SIZE, "irq"); + direct_call(param1); + } +} + /* ONLY called from entry.S:intr_extint() */ void do_cpu_irq_mask(struct pt_regs *regs) { @@ -364,7 +418,7 @@ void do_cpu_irq_mask(struct pt_regs *regs) goto set_out; } #endif - generic_handle_irq(irq); + execute_on_irq_stack(&generic_handle_irq, irq); out: irq_exit(); @@ -423,3 +477,24 @@ void __init init_IRQ(void) } +DEFINE_PER_CPU(union irq_stack_union, irq_stack_union); + +asmlinkage void do_softirq(void) +{ + __u32 pending; + unsigned long flags; + + if (in_interrupt()) + return; + + local_irq_save(flags); + + pending = local_softirq_pending(); + + /* Switch to interrupt stack */ + if (pending) { + execute_on_irq_stack(&__do_softirq, 0); + WARN_ON_ONCE(softirq_count()); + } + local_irq_restore(flags); +} --------------000209020801060300070501--