parisc: implement irq stacks - part 2 (v2)

This patch fixes few build issues which were introduced with the last
irq stack patch, e.g. the combination of stack overflow check and irq
stack.

Furthermore we now do proper locking and change the irq bh handler
to use the irq stack as well.

In /proc/interrupts one now can monitor how huge the irq stack has grown
and how often it was preferred over the kernel stack.

IRQ stacks are now enabled by default just to make sure that we not
overflow the kernel stack by accident.

Signed-off-by: Helge Deller <deller@gmx.de>

1 files changed, 87 insertions, 14 deletions

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 */