5 files changed, 102 insertions, 17 deletions

diff --git a/arch/parisc/Kconfig b/arch/parisc/Kconfig
index cad060f288cf..6507dabdd5dd 100644
--- a/arch/parisc/Kconfig
+++ b/arch/parisc/Kconfig
@@ -245,7 +245,7 @@ config SMP
 
 config IRQSTACKS
         bool "Use separate kernel stacks when processing interrupts"
-        default n
+        default y
         help
           If you say Y here the kernel will use separate kernel stacks
           for handling hard and soft interrupts.  This can help avoid
diff --git a/arch/parisc/include/asm/hardirq.h b/arch/parisc/include/asm/hardirq.h
index 12373c4dabab..c19f7138ba48 100644
--- a/arch/parisc/include/asm/hardirq.h
+++ b/arch/parisc/include/asm/hardirq.h
@@ -11,10 +11,18 @@
 #include <linux/threads.h>
 #include <linux/irq.h>
 
+#ifdef CONFIG_IRQSTACKS
+#define __ARCH_HAS_DO_SOFTIRQ
+#endif
+
 typedef struct {
         unsigned int __softirq_pending;
 #ifdef CONFIG_DEBUG_STACKOVERFLOW
         unsigned int kernel_stack_usage;
+#ifdef CONFIG_IRQSTACKS
+        unsigned int irq_stack_usage;
+        unsigned int irq_stack_counter;
+#endif
 #endif
 #ifdef CONFIG_SMP
         unsigned int irq_resched_count;
@@ -28,6 +36,7 @@ DECLARE_PER_CPU_SHARED_ALIGNED(irq_cpustat_t, irq_stat);
 #define __ARCH_IRQ_STAT
 #define __IRQ_STAT(cpu, member) (irq_stat[cpu].member)
 #define inc_irq_stat(member)    this_cpu_inc(irq_stat.member)
+#define __inc_irq_stat(member)  __this_cpu_inc(irq_stat.member)
 #define local_softirq_pending() this_cpu_read(irq_stat.__softirq_pending)
 
 #define __ARCH_SET_SOFTIRQ_PENDING
diff --git a/arch/parisc/include/asm/processor.h b/arch/parisc/include/asm/processor.h
index 064015547d1e..cfbc43929cf6 100644
--- a/arch/parisc/include/asm/processor.h
+++ b/arch/parisc/include/asm/processor.h
@@ -63,10 +63,13 @@
  */
 #ifdef __KERNEL__
 
+#include <linux/spinlock_types.h>
+
 #define IRQ_STACK_SIZE      (4096 << 2) /* 16k irq stack size */
 
 union irq_stack_union {
         unsigned long stack[IRQ_STACK_SIZE/sizeof(unsigned long)];
+        raw_spinlock_t lock;
 };
 
 DECLARE_PER_CPU(union irq_stack_union, irq_stack_union);
diff --git a/arch/parisc/kernel/irq.c b/arch/parisc/kernel/irq.c
index e255db0bb761..55237a70e197 100644
--- a/arch/parisc/kernel/irq.c
+++ b/arch/parisc/kernel/irq.c
@@ -166,22 +166,32 @@ int arch_show_interrupts(struct seq_file *p, int prec)
         seq_printf(p, "%*s: ", prec, "STK");
         for_each_online_cpu(j)
                 seq_printf(p, "%10u ", irq_stats(j)->kernel_stack_usage);
-        seq_printf(p, "  Kernel stack usage\n");
+        seq_puts(p, "  Kernel stack usage\n");
+# ifdef CONFIG_IRQSTACKS
+        seq_printf(p, "%*s: ", prec, "IST");
+        for_each_online_cpu(j)
+                seq_printf(p, "%10u ", irq_stats(j)->irq_stack_usage);
+        seq_puts(p, "  Interrupt stack usage\n");
+        seq_printf(p, "%*s: ", prec, "ISC");
+        for_each_online_cpu(j)
+                seq_printf(p, "%10u ", irq_stats(j)->irq_stack_counter);
+        seq_puts(p, "  Interrupt stack usage counter\n");
+# endif
 #endif
 #ifdef CONFIG_SMP
         seq_printf(p, "%*s: ", prec, "RES");
         for_each_online_cpu(j)
                 seq_printf(p, "%10u ", irq_stats(j)->irq_resched_count);
-        seq_printf(p, "  Rescheduling interrupts\n");
+        seq_puts(p, "  Rescheduling interrupts\n");
         seq_printf(p, "%*s: ", prec, "CAL");
         for_each_online_cpu(j)
                 seq_printf(p, "%10u ", irq_stats(j)->irq_call_count);
-        seq_printf(p, "  Function call interrupts\n");
+        seq_puts(p, "  Function call interrupts\n");
 #endif
         seq_printf(p, "%*s: ", prec, "TLB");
         for_each_online_cpu(j)
                 seq_printf(p, "%10u ", irq_stats(j)->irq_tlb_count);
-        seq_printf(p, "  TLB shootdowns\n");
+        seq_puts(p, "  TLB shootdowns\n");
         return 0;
 }
 
@@ -378,6 +388,7 @@ static inline void stack_overflow_check(struct pt_regs *regs)
         unsigned long sp = regs->gr[30];
         unsigned long stack_usage;
         unsigned int *last_usage;
+        int cpu = smp_processor_id();
 
         /* if sr7 != 0, we interrupted a userspace process which we do not want
          * to check for stack overflow. We will only check the kernel stack. */
@@ -386,7 +397,31 @@ static inline void stack_overflow_check(struct pt_regs *regs)
 
         /* calculate kernel stack usage */
         stack_usage = sp - stack_start;
-        last_usage = &per_cpu(irq_stat.kernel_stack_usage, smp_processor_id());
+#ifdef CONFIG_IRQSTACKS
+        if (likely(stack_usage <= THREAD_SIZE))
+                goto check_kernel_stack; /* found kernel stack */
+
+        /* check irq stack usage */
+        stack_start = (unsigned long) &per_cpu(irq_stack_union, cpu).stack;
+        stack_usage = sp - stack_start;
+
+        last_usage = &per_cpu(irq_stat.irq_stack_usage, cpu);
+        if (unlikely(stack_usage > *last_usage))
+                *last_usage = stack_usage;
+
+        if (likely(stack_usage < (IRQ_STACK_SIZE - STACK_MARGIN)))
+                return;
+
+        pr_emerg("stackcheck: %s will most likely overflow irq stack "
+                 "(sp:%lx, stk bottom-top:%lx-%lx)\n",
+                current->comm, sp, stack_start, stack_start + IRQ_STACK_SIZE);
+        goto panic_check;
+
+check_kernel_stack:
+#endif
+
+        /* check kernel stack usage */
+        last_usage = &per_cpu(irq_stat.kernel_stack_usage, cpu);
 
         if (unlikely(stack_usage > *last_usage))
                 *last_usage = stack_usage;
@@ -398,31 +433,69 @@ static inline void stack_overflow_check(struct pt_regs *regs)
                  "(sp:%lx, stk bottom-top:%lx-%lx)\n",
                 current->comm, sp, stack_start, stack_start + THREAD_SIZE);
 
+#ifdef CONFIG_IRQSTACKS
+panic_check:
+#endif
         if (sysctl_panic_on_stackoverflow)
                 panic("low stack detected by irq handler - check messages\n");
 #endif
 }
 
 #ifdef CONFIG_IRQSTACKS
-DEFINE_PER_CPU(union irq_stack_union, irq_stack_union);
+DEFINE_PER_CPU(union irq_stack_union, irq_stack_union) = {
+                .lock = __RAW_SPIN_LOCK_UNLOCKED((irq_stack_union).lock)
+        };
 
 static void execute_on_irq_stack(void *func, unsigned long param1)
 {
-        unsigned long *irq_stack_start;
+        union irq_stack_union *union_ptr;
         unsigned long irq_stack;
-        int cpu = smp_processor_id();
+        raw_spinlock_t *irq_stack_in_use;
 
-        irq_stack_start = &per_cpu(irq_stack_union, cpu).stack[0];
-        irq_stack = (unsigned long) irq_stack_start;
-        irq_stack = ALIGN(irq_stack, 16); /* align for stack frame usage */
+        union_ptr = &per_cpu(irq_stack_union, smp_processor_id());
+        irq_stack = (unsigned long) &union_ptr->stack;
+        irq_stack = ALIGN(irq_stack + sizeof(irq_stack_union.lock),
+                         64); /* align for stack frame usage */
 
-        BUG_ON(*irq_stack_start); /* report bug if we were called recursive. */
-        *irq_stack_start = 1;
+        /* We may be called recursive. If we are already using the irq stack,
+         * just continue to use it. Use spinlocks to serialize
+         * the irq stack usage.
+         */
+        irq_stack_in_use = &union_ptr->lock;
+        if (!raw_spin_trylock(irq_stack_in_use)) {
+                void (*direct_call)(unsigned long p1) = func;
+
+                /* We are using the IRQ stack already.
+                 * Do direct call on current stack. */
+                direct_call(param1);
+                return;
+        }
 
         /* This is where we switch to the IRQ stack. */
         call_on_stack(param1, func, irq_stack);
 
-        *irq_stack_start = 0;
+        __inc_irq_stat(irq_stack_counter);
+
+        /* free up irq stack usage. */
+        do_raw_spin_unlock(irq_stack_in_use);
+}
+
+asmlinkage void do_softirq(void)
+{
+        __u32 pending;
+        unsigned long flags;
+
+        if (in_interrupt())
+                return;
+
+        local_irq_save(flags);
+
+        pending = local_softirq_pending();
+
+        if (pending)
+                execute_on_irq_stack(__do_softirq, 0);
+
+        local_irq_restore(flags);
 }
 #endif /* CONFIG_IRQSTACKS */
 
diff --git a/arch/parisc/mm/init.c b/arch/parisc/mm/init.c
index ce939ac8622b..1c965642068b 100644
--- a/arch/parisc/mm/init.c
+++ b/arch/parisc/mm/init.c
@@ -1069,7 +1069,7 @@ void flush_tlb_all(void)
 {
         int do_recycle;
 
-        inc_irq_stat(irq_tlb_count);
+        __inc_irq_stat(irq_tlb_count);
         do_recycle = 0;
         spin_lock(&sid_lock);
         if (dirty_space_ids > RECYCLE_THRESHOLD) {
@@ -1090,7 +1090,7 @@ void flush_tlb_all(void)
 #else
 void flush_tlb_all(void)
 {
-        inc_irq_stat(irq_tlb_count);
+        __inc_irq_stat(irq_tlb_count);
         spin_lock(&sid_lock);
         flush_tlb_all_local(NULL);
         recycle_sids();