parisc: implement irq stacks

Default kernel stack size on parisc is 16k.  During tests we found that the
kernel stack can easily grow beyond 13k, which leaves 3k left for irq
processing.

This patch adds the possibility to activate an additional stack of 16k per CPU
which is being used during irq processing.  This implementation does not yet
uses this irq stack for the irq bh handler.

The assembler code for call_on_stack was heavily cleaned up by John
David Anglin.

CC: John David Anglin <dave.anglin@bell.net>
Signed-off-by: Helge Deller <deller@gmx.de>

diff --git a/arch/parisc/Kconfig b/arch/parisc/Kconfig
index fe4afb0f152fe7f9780f32533c0f7d1b09ed66a3..cad060f288cf51e089bfb9cf7b6e879064bc0989 100644 (file)
--- a/arch/parisc/Kconfig
+++ b/arch/parisc/Kconfig
@@ -243,6 +243,14 @@ config SMP
 
          If you don't know what to do here, say N.
 
+config IRQSTACKS
+       bool "Use separate kernel stacks when processing interrupts"
+       default n
+       help
+         If you say Y here the kernel will use separate kernel stacks
+         for handling hard and soft interrupts.  This can help avoid
+         overflowing the process kernel stacks.
+
 config HOTPLUG_CPU
        bool
        default y if SMP

diff --git a/arch/parisc/include/asm/processor.h b/arch/parisc/include/asm/processor.h
index 09b54a57a48d025283af4816d319e14a911e6158..242f06a5fbd8746587ae018513e8c6c258632047 100644 (file)
--- 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").
@@ -60,6 +58,23 @@
 
 #ifndef __ASSEMBLY__
 
+/*
+ * IRQ STACK - used for irq handler
+ */
+#ifdef __KERNEL__
+
+#define IRQ_STACK_SIZE      (4096 << 2) /* 16k irq stack size */
+
+union irq_stack_union {
+       unsigned long stack[IRQ_STACK_SIZE/sizeof(unsigned long)];
+};
+
+DECLARE_PER_CPU(union irq_stack_union, irq_stack_union);
+
+void call_on_stack(unsigned long p1, void *func, unsigned long new_stack);
+
+#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/kernel/entry.S b/arch/parisc/kernel/entry.S
index 3f3326d876f796de45b59c9d7d5c19f4add1af0a..4bb96ad9b0b14ddd1cb066bc21b304d861059f38 100644 (file)
--- a/arch/parisc/kernel/entry.S
+++ b/arch/parisc/kernel/entry.S
@@ -2010,6 +2010,47 @@ ftrace_stub:
 ENDPROC(return_to_handler)
 #endif /* CONFIG_FUNCTION_TRACER */
 
+#ifdef CONFIG_IRQSTACKS
+/* void call_on_stack(unsigned long param1, void *func,
+                     unsigned long new_stack) */
+ENTRY(call_on_stack)
+       copy    %sp, %r1
+
+       /* Regarding the HPPA calling conventions for function pointers,
+          we assume the PIC register is not changed across call.  For
+          CONFIG_64BIT, the argument pointer is left to point at the
+          argument region allocated for the call to call_on_stack. */
+# ifdef CONFIG_64BIT
+       /* Switch to new stack.  We allocate two 128 byte frames.  */
+       ldo     256(%arg2), %sp
+       /* Save previous stack pointer and return pointer in frame marker */
+       STREG   %rp, -144(%sp)
+       /* Calls always use function descriptor */
+       LDREG   16(%arg1), %arg1
+       bve,l   (%arg1), %rp
+       STREG   %r1, -136(%sp)
+       LDREG   -144(%sp), %rp
+       bve     (%rp)
+       LDREG   -136(%sp), %sp
+# else
+       /* Switch to new stack.  We allocate two 64 byte frames.  */
+       ldo     128(%arg2), %sp
+       /* Save previous stack pointer and return pointer in frame marker */
+       STREG   %r1, -68(%sp)
+       STREG   %rp, -84(%sp)
+       /* Calls use function descriptor if PLABEL bit is set */
+       bb,>=,n %arg1, 30, 1f
+       depwi   0,31,2, %arg1
+       LDREG   0(%arg1), %arg1
+1:
+       be,l    0(%sr4,%arg1), %sr0, %r31
+       copy    %r31, %rp
+       LDREG   -84(%sp), %rp
+       bv      (%rp)
+       LDREG   -68(%sp), %sp
+# endif /* CONFIG_64BIT */
+ENDPROC(call_on_stack)
+#endif /* CONFIG_IRQSTACKS */
 
 get_register:
        /*

diff --git a/arch/parisc/kernel/irq.c b/arch/parisc/kernel/irq.c
index 61e51ac85659d91a70096614b6a1b435027fd059..810f9cf89e4860255b2e882fb1d6e0763d523eb6 100644 (file)
--- a/arch/parisc/kernel/irq.c
+++ b/arch/parisc/kernel/irq.c
@@ -358,6 +358,29 @@ static inline void stack_overflow_check(struct pt_regs *regs)
 #endif
 }
 
+#ifdef CONFIG_IRQSTACKS
+DEFINE_PER_CPU(union irq_stack_union, irq_stack_union);
+
+static void execute_on_irq_stack(void *func, unsigned long param1)
+{
+       unsigned long *irq_stack_start;
+       unsigned long irq_stack;
+       int cpu = smp_processor_id();
+
+       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 */
+
+       BUG_ON(*irq_stack_start); /* report bug if we were called recursive. */
+       *irq_stack_start = 1;
+
+       /* This is where we switch to the IRQ stack. */
+       call_on_stack(param1, func, irq_stack);
+
+       *irq_stack_start = 0;
+}
+#endif /* CONFIG_IRQSTACKS */
+
 /* ONLY called from entry.S:intr_extint() */
 void do_cpu_irq_mask(struct pt_regs *regs)
 {
@@ -393,7 +416,12 @@ void do_cpu_irq_mask(struct pt_regs *regs)
        }
 #endif
        stack_overflow_check(regs);
+
+#ifdef CONFIG_IRQSTACKS
+       execute_on_irq_stack(&generic_handle_irq, irq);
+#else
        generic_handle_irq(irq);
+#endif /* CONFIG_IRQSTACKS */
 
  out:
        irq_exit();