PREEMPT_RT preempts softirqs and the current implementation avoids do_softirq_own_stack() and only uses __do_softirq().
Disable the unused softirqs stacks on PREEMPT_RT to safe some memory and ensure that do_softirq_own_stack() is not used bwcause it is not expected. Signed-off-by: Sebastian Andrzej Siewior <bige...@linutronix.de> --- Initially I aimed only for the asm-generic bits and arm since I have most bits of the port ready. Arnd then suggested to do all arches at once and here it is. I tried to keep it minimal in sense that I didn't remove the dedicated softirq-stacks on parisc or powerpc for instance. That would add another few ifdefs and I don't know if we manage to get it up and running on parisc. I do have the missing bits for powerpc however ;) arch/arm/kernel/irq.c | 3 ++- arch/parisc/kernel/irq.c | 2 ++ arch/powerpc/kernel/irq.c | 4 ++++ arch/s390/include/asm/softirq_stack.h | 3 ++- arch/sh/kernel/irq.c | 2 ++ arch/sparc/kernel/irq_64.c | 2 ++ include/asm-generic/softirq_stack.h | 2 +- 7 files changed, 15 insertions(+), 3 deletions(-) diff --git a/arch/arm/kernel/irq.c b/arch/arm/kernel/irq.c index 5c6f8d11a3ce5..034cb48c9eeb8 100644 --- a/arch/arm/kernel/irq.c +++ b/arch/arm/kernel/irq.c @@ -70,6 +70,7 @@ static void __init init_irq_stacks(void) } } +#ifndef CONFIG_PREEMPT_RT static void ____do_softirq(void *arg) { __do_softirq(); @@ -80,7 +81,7 @@ void do_softirq_own_stack(void) call_with_stack(____do_softirq, NULL, __this_cpu_read(irq_stack_ptr)); } - +#endif #endif int arch_show_interrupts(struct seq_file *p, int prec) diff --git a/arch/parisc/kernel/irq.c b/arch/parisc/kernel/irq.c index 0fe2d79fb123f..eba193bcdab1b 100644 --- a/arch/parisc/kernel/irq.c +++ b/arch/parisc/kernel/irq.c @@ -480,10 +480,12 @@ static void execute_on_irq_stack(void *func, unsigned long param1) *irq_stack_in_use = 1; } +#ifndef CONFIG_PREEMPT_RT void do_softirq_own_stack(void) { execute_on_irq_stack(__do_softirq, 0); } +#endif #endif /* CONFIG_IRQSTACKS */ /* ONLY called from entry.S:intr_extint() */ diff --git a/arch/powerpc/kernel/irq.c b/arch/powerpc/kernel/irq.c index dd09919c3c668..0822a274a549c 100644 --- a/arch/powerpc/kernel/irq.c +++ b/arch/powerpc/kernel/irq.c @@ -611,6 +611,7 @@ static inline void check_stack_overflow(void) } } +#ifndef CONFIG_PREEMPT_RT static __always_inline void call_do_softirq(const void *sp) { /* Temporarily switch r1 to sp, call __do_softirq() then restore r1. */ @@ -629,6 +630,7 @@ static __always_inline void call_do_softirq(const void *sp) "r11", "r12" ); } +#endif static __always_inline void call_do_irq(struct pt_regs *regs, void *sp) { @@ -747,10 +749,12 @@ void *mcheckirq_ctx[NR_CPUS] __read_mostly; void *softirq_ctx[NR_CPUS] __read_mostly; void *hardirq_ctx[NR_CPUS] __read_mostly; +#ifndef CONFIG_PREEMPT_RT void do_softirq_own_stack(void) { call_do_softirq(softirq_ctx[smp_processor_id()]); } +#endif irq_hw_number_t virq_to_hw(unsigned int virq) { diff --git a/arch/s390/include/asm/softirq_stack.h b/arch/s390/include/asm/softirq_stack.h index fd17f25704bd5..af68d6c1d5840 100644 --- a/arch/s390/include/asm/softirq_stack.h +++ b/arch/s390/include/asm/softirq_stack.h @@ -5,9 +5,10 @@ #include <asm/lowcore.h> #include <asm/stacktrace.h> +#ifndef CONFIG_PREEMPT_RT static inline void do_softirq_own_stack(void) { call_on_stack(0, S390_lowcore.async_stack, void, __do_softirq); } - +#endif #endif /* __ASM_S390_SOFTIRQ_STACK_H */ diff --git a/arch/sh/kernel/irq.c b/arch/sh/kernel/irq.c index ef0f0827cf575..2d3eca8fee011 100644 --- a/arch/sh/kernel/irq.c +++ b/arch/sh/kernel/irq.c @@ -149,6 +149,7 @@ void irq_ctx_exit(int cpu) hardirq_ctx[cpu] = NULL; } +#ifndef CONFIG_PREEMPT_RT void do_softirq_own_stack(void) { struct thread_info *curctx; @@ -176,6 +177,7 @@ void do_softirq_own_stack(void) "r5", "r6", "r7", "r8", "r9", "r15", "t", "pr" ); } +#endif #else static inline void handle_one_irq(unsigned int irq) { diff --git a/arch/sparc/kernel/irq_64.c b/arch/sparc/kernel/irq_64.c index c8848bb681a11..41fa1be980a33 100644 --- a/arch/sparc/kernel/irq_64.c +++ b/arch/sparc/kernel/irq_64.c @@ -855,6 +855,7 @@ void __irq_entry handler_irq(int pil, struct pt_regs *regs) set_irq_regs(old_regs); } +#ifndef CONFIG_PREEMPT_RT void do_softirq_own_stack(void) { void *orig_sp, *sp = softirq_stack[smp_processor_id()]; @@ -869,6 +870,7 @@ void do_softirq_own_stack(void) __asm__ __volatile__("mov %0, %%sp" : : "r" (orig_sp)); } +#endif #ifdef CONFIG_HOTPLUG_CPU void fixup_irqs(void) diff --git a/include/asm-generic/softirq_stack.h b/include/asm-generic/softirq_stack.h index eceeecf6a5bd8..d3e2d81656e04 100644 --- a/include/asm-generic/softirq_stack.h +++ b/include/asm-generic/softirq_stack.h @@ -2,7 +2,7 @@ #ifndef __ASM_GENERIC_SOFTIRQ_STACK_H #define __ASM_GENERIC_SOFTIRQ_STACK_H -#ifdef CONFIG_HAVE_SOFTIRQ_ON_OWN_STACK +#if defined(CONFIG_HAVE_SOFTIRQ_ON_OWN_STACK) && !defined(CONFIG_PREEMPT_RT) void do_softirq_own_stack(void); #else static inline void do_softirq_own_stack(void) -- 2.36.1