sh: Fixup 4K irq stacks.

There was a clobber issue with the register we were saving
the stack in, so we switch to a register that we handle in
the clobber list properly already.

This also follows the x86 changes for allowing the softirq
checks from hardirq context.

Signed-off-by: Paul Mundt <lethal@linux-sh.org>

1 files changed, 18 insertions, 7 deletions

diff --git a/arch/sh/kernel/irq.c b/arch/sh/kernel/irq.c
index edf4d2d21336..46a19e07abd3 100644
--- a/arch/sh/kernel/irq.c
+++ b/arch/sh/kernel/irq.c
@@ -78,8 +78,8 @@ union irq_ctx {
         u32                     stack[THREAD_SIZE/sizeof(u32)];
 };
 
-static union irq_ctx *hardirq_ctx[NR_CPUS];
-static union irq_ctx *softirq_ctx[NR_CPUS];
+static union irq_ctx *hardirq_ctx[NR_CPUS] __read_mostly;
+static union irq_ctx *softirq_ctx[NR_CPUS] __read_mostly;
 #endif
 
 asmlinkage int do_IRQ(unsigned long r4, unsigned long r5,
@@ -136,17 +136,24 @@ asmlinkage int do_IRQ(unsigned long r4, unsigned long r5,
                 irqctx->tinfo.task = curctx->tinfo.task;
                 irqctx->tinfo.previous_sp = current_stack_pointer;
 
+                /*
+                 * Copy the softirq bits in preempt_count so that the
+                 * softirq checks work in the hardirq context.
+                 */
+                irqctx->tinfo.preempt_count =
+                        (irqctx->tinfo.preempt_count & ~SOFTIRQ_MASK) |
+                        (curctx->tinfo.preempt_count & SOFTIRQ_MASK);
+
                 __asm__ __volatile__ (
                         "mov    %0, r4          \n"
-                        "mov    r15, r9         \n"
+                        "mov    r15, r8         \n"
                         "jsr    @%1             \n"
                         /* swith to the irq stack */
                         " mov   %2, r15         \n"
                         /* restore the stack (ring zero) */
-                        "mov    r9, r15         \n"
+                        "mov    r8, r15         \n"
                         : /* no outputs */
                         : "r" (irq), "r" (generic_handle_irq), "r" (isp)
-                        /* XXX: A somewhat excessive clobber list? -PFM */
                         : "memory", "r0", "r1", "r2", "r3", "r4",
                           "r5", "r6", "r7", "r8", "t", "pr"
                 );
@@ -194,7 +201,7 @@ void irq_ctx_init(int cpu)
         irqctx->tinfo.task              = NULL;
         irqctx->tinfo.exec_domain       = NULL;
         irqctx->tinfo.cpu               = cpu;
-        irqctx->tinfo.preempt_count     = SOFTIRQ_OFFSET;
+        irqctx->tinfo.preempt_count     = 0;
         irqctx->tinfo.addr_limit        = MAKE_MM_SEG(0);
 
         softirq_ctx[cpu] = irqctx;
@@ -240,10 +247,14 @@ asmlinkage void do_softirq(void)
                         "mov    r9, r15         \n"
                         : /* no outputs */
                         : "r" (__do_softirq), "r" (isp)
-                        /* XXX: A somewhat excessive clobber list? -PFM */
                         : "memory", "r0", "r1", "r2", "r3", "r4",
                           "r5", "r6", "r7", "r8", "r9", "r15", "t", "pr"
                 );
+
+                /*
+                 * Shouldnt happen, we returned above if in_interrupt():
+                 */
+                WARN_ON_ONCE(softirq_count());
         }
 
         local_irq_restore(flags);