[PATCH] x86_64: Switch to the interrupt stack when running a softirq in local_bh_enable()

This avoids some potential stack overflows with very deep softirq callchains.
i386 does this too.

TOADD CFI annotation

Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

4 files changed, 35 insertions, 2 deletions

diff --git a/arch/x86_64/kernel/entry.S b/arch/x86_64/kernel/entry.S
index 0696e025dce5..096d470e280f 100644
--- a/arch/x86_64/kernel/entry.S
+++ b/arch/x86_64/kernel/entry.S
@@ -918,3 +918,15 @@ ENTRY(machine_check)
 ENTRY(call_debug)
        zeroentry do_call_debug
 
+ENTRY(call_softirq)
+        movq %gs:pda_irqstackptr,%rax
+        pushq %r15
+        movq %rsp,%r15
+        incl %gs:pda_irqcount
+        cmove %rax,%rsp
+        call __do_softirq
+        movq %r15,%rsp
+        decl %gs:pda_irqcount
+        popq %r15
+        ret
+
diff --git a/arch/x86_64/kernel/irq.c b/arch/x86_64/kernel/irq.c
index cc3fb85f5145..849a20aec7ca 100644
--- a/arch/x86_64/kernel/irq.c
+++ b/arch/x86_64/kernel/irq.c
@@ -135,3 +135,22 @@ void fixup_irqs(cpumask_t map)
         local_irq_disable();
 }
 #endif
+
+extern void call_softirq(void);
+
+asmlinkage void do_softirq(void)
+{
+        __u32 pending;
+        unsigned long flags;
+
+        if (in_interrupt())
+                return;
+
+        local_irq_save(flags);
+        pending = local_softirq_pending();
+        /* Switch to interrupt stack */
+        if (pending)
+                call_softirq();
+        local_irq_restore(flags);
+}
+EXPORT_SYMBOL(do_softirq);
diff --git a/include/asm-x86_64/irq.h b/include/asm-x86_64/irq.h
index eb3b7aa9eb9f..4482657777bb 100644
--- a/include/asm-x86_64/irq.h
+++ b/include/asm-x86_64/irq.h
@@ -57,4 +57,6 @@ int handle_IRQ_event(unsigned int, struct pt_regs *, struct irqaction *);
 extern void fixup_irqs(cpumask_t map);
 #endif
 
+#define __ARCH_HAS_DO_SOFTIRQ 1
+
 #endif /* _ASM_IRQ_H */
diff --git a/kernel/softirq.c b/kernel/softirq.c
index b4ab6af1dea8..31007d6542cc 100644
--- a/kernel/softirq.c
+++ b/kernel/softirq.c
@@ -86,7 +86,7 @@ restart:
         /* Reset the pending bitmask before enabling irqs */
         local_softirq_pending() = 0;
 
-        local_irq_enable();
+        //local_irq_enable();
 
         h = softirq_vec;
 
@@ -99,7 +99,7 @@ restart:
                 pending >>= 1;
         } while (pending);
 
-        local_irq_disable();
+        //local_irq_disable();
 
         pending = local_softirq_pending();
         if (pending && --max_restart)