[PATCH] i386: Fix softirq accounting with 4K stacks

Copy the softirq bits in preempt_count from the current context into the
hardirq context when using 4K stacks to make the softirq_count macro work
correctly and thereby fix softirq cpu time accounting.

Signed-off-by: Björn Steinbrink <B.Steinbrink@gmx.de>
Acked-by: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 8 insertions, 0 deletions

diff --git a/arch/i386/kernel/irq.c b/arch/i386/kernel/irq.c
index 248e922ee13a..49ce4c31b713 100644
--- a/arch/i386/kernel/irq.c
+++ b/arch/i386/kernel/irq.c
@@ -95,6 +95,14 @@ fastcall unsigned int do_IRQ(struct pt_regs *regs)
                 irqctx->tinfo.task = curctx->tinfo.task;
                 irqctx->tinfo.previous_esp = 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(
                         "       xchgl   %%ebx,%%esp      \n"
                         "       call    __do_IRQ         \n"