i386, dumpstack: use x86_64's method to account die_nest_count

oops_begin/oops_end should always be used in pairs. On x86_64
oops_begin increments die_nest_count, and oops_end decrements
die_nest_count. Doing this makes oops_begin and oops_end equal
to the x86_64 versions.

Signed-off-by: Alexander van Heukelum <heukelum@fastmail.fm>
Acked-by: Neil Horman <nhorman@tuxdriver.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 17 insertions, 12 deletions

diff --git a/arch/x86/kernel/dumpstack_32.c b/arch/x86/kernel/dumpstack_32.c
index a29b88ffa346..7c7d691b32be 100644
--- a/arch/x86/kernel/dumpstack_32.c
+++ b/arch/x86/kernel/dumpstack_32.c
@@ -289,21 +289,24 @@ static unsigned int die_nest_count;
 
 unsigned __kprobes long oops_begin(void)
 {
+        int cpu;
         unsigned long flags;
 
         oops_enter();
 
-        if (die_owner != raw_smp_processor_id()) {
-                console_verbose();
-                raw_local_irq_save(flags);
-                __raw_spin_lock(&die_lock);
-                die_owner = smp_processor_id();
-                die_nest_count = 0;
-                bust_spinlocks(1);
-        } else {
-                raw_local_irq_save(flags);
+        /* racy, but better than risking deadlock. */
+        raw_local_irq_save(flags);
+        cpu = smp_processor_id();
+        if (!__raw_spin_trylock(&die_lock)) {
+                if (cpu == die_owner)
+                        /* nested oops. should stop eventually */;
+                else
+                        __raw_spin_lock(&die_lock);
         }
         die_nest_count++;
+        die_owner = cpu;
+        console_verbose();
+        bust_spinlocks(1);
         return flags;
 }
 
@@ -315,13 +318,15 @@ void __kprobes oops_end(unsigned long flags, struct pt_regs *regs, int signr)
         bust_spinlocks(0);
         die_owner = -1;
         add_taint(TAINT_DIE);
-        __raw_spin_unlock(&die_lock);
+        die_nest_count--;
+        if (!die_nest_count)
+                /* Nest count reaches zero, release the lock. */
+                __raw_spin_unlock(&die_lock);
         raw_local_irq_restore(flags);
-
         oops_exit();
+
         if (!signr)
                 return;
-
         if (in_interrupt())
                 panic("Fatal exception in interrupt");
         if (panic_on_oops)