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Subject[RFC PATCH 8/8] powerpc/irq: drop softirq stack
Date
There are two IRQ stacks: softirq_ctx and hardirq_ctx

do_softirq_own_stack() switches stack to softirq_ctx
do_IRQ() switches stack to hardirq_ctx

However, when soft and hard IRQs are nested, only one of the two
stacks is used:
- When on softirq stack, do_IRQ() doesn't switch to hardirq stack.
- irq_exit() runs softirqs on hardirq stack.

There is no added value in having two IRQ stacks as only one is
used when hard and soft irqs are nested. Remove softirq_ctx and
use hardirq_ctx for both hard and soft IRQs.

Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
---
arch/powerpc/include/asm/irq.h | 1 -
arch/powerpc/kernel/irq.c | 8 +++-----
arch/powerpc/kernel/process.c | 4 ----
arch/powerpc/kernel/setup_32.c | 4 +---
arch/powerpc/kernel/setup_64.c | 4 +---
5 files changed, 5 insertions(+), 16 deletions(-)

diff --git a/arch/powerpc/include/asm/irq.h b/arch/powerpc/include/asm/irq.h
index e4a92f0b4ad4..7cb2c76aa3ed 100644
--- a/arch/powerpc/include/asm/irq.h
+++ b/arch/powerpc/include/asm/irq.h
@@ -54,7 +54,6 @@ extern void *mcheckirq_ctx[NR_CPUS];
* Per-cpu stacks for handling hard and soft interrupts.
*/
extern void *hardirq_ctx[NR_CPUS];
-extern void *softirq_ctx[NR_CPUS];

#ifdef CONFIG_PPC64
void call_do_softirq(void *sp);
diff --git a/arch/powerpc/kernel/irq.c b/arch/powerpc/kernel/irq.c
index a1122ef4a16c..3af0d1897354 100644
--- a/arch/powerpc/kernel/irq.c
+++ b/arch/powerpc/kernel/irq.c
@@ -680,15 +680,14 @@ void __do_irq(struct pt_regs *regs)

void do_IRQ(struct pt_regs *regs)
{
- void *cursp, *irqsp, *sirqsp;
+ void *cursp, *irqsp;

/* Switch to the irq stack to handle this */
cursp = (void *)(stack_pointer() & ~(THREAD_SIZE - 1));
irqsp = hardirq_ctx[raw_smp_processor_id()];
- sirqsp = softirq_ctx[raw_smp_processor_id()];

/* Already there ? Otherwise switch stack and call */
- if (unlikely(cursp == irqsp || cursp == sirqsp))
+ if (unlikely(cursp == irqsp))
__do_irq(regs);
else
call_do_irq(regs, irqsp);
@@ -706,12 +705,11 @@ void *dbgirq_ctx[NR_CPUS] __read_mostly;
void *mcheckirq_ctx[NR_CPUS] __read_mostly;
#endif

-void *softirq_ctx[NR_CPUS] __read_mostly;
void *hardirq_ctx[NR_CPUS] __read_mostly;

void do_softirq_own_stack(void)
{
- call_do_softirq(softirq_ctx[smp_processor_id()]);
+ call_do_softirq(hardirq_ctx[smp_processor_id()]);
}

irq_hw_number_t virq_to_hw(unsigned int virq)
diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c
index 49d0ebf28ab9..be3e64cf28b4 100644
--- a/arch/powerpc/kernel/process.c
+++ b/arch/powerpc/kernel/process.c
@@ -1963,10 +1963,6 @@ static inline int valid_irq_stack(unsigned long sp, struct task_struct *p,
if (sp >= stack_page && sp <= stack_page + THREAD_SIZE - nbytes)
return 1;

- stack_page = (unsigned long)softirq_ctx[cpu];
- if (sp >= stack_page && sp <= stack_page + THREAD_SIZE - nbytes)
- return 1;
-
return 0;
}

diff --git a/arch/powerpc/kernel/setup_32.c b/arch/powerpc/kernel/setup_32.c
index dcffe927f5b9..8752aae06177 100644
--- a/arch/powerpc/kernel/setup_32.c
+++ b/arch/powerpc/kernel/setup_32.c
@@ -155,10 +155,8 @@ void __init irqstack_early_init(void)

/* interrupt stacks must be in lowmem, we get that for free on ppc32
* as the memblock is limited to lowmem by default */
- for_each_possible_cpu(i) {
- softirq_ctx[i] = alloc_stack();
+ for_each_possible_cpu(i)
hardirq_ctx[i] = alloc_stack();
- }
}

#if defined(CONFIG_BOOKE) || defined(CONFIG_40x)
diff --git a/arch/powerpc/kernel/setup_64.c b/arch/powerpc/kernel/setup_64.c
index 6104917a282d..96ee7627eda6 100644
--- a/arch/powerpc/kernel/setup_64.c
+++ b/arch/powerpc/kernel/setup_64.c
@@ -652,10 +652,8 @@ void __init irqstack_early_init(void)
* cannot afford to take SLB misses on them. They are not
* accessed in realmode.
*/
- for_each_possible_cpu(i) {
- softirq_ctx[i] = alloc_stack(limit, i);
+ for_each_possible_cpu(i)
hardirq_ctx[i] = alloc_stack(limit, i);
- }
}

#ifdef CONFIG_PPC_BOOK3E
--
2.13.3
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