powerpc: Rework die()

Our die() code was based off a very old x86 version. Update it to
mirror the current x86 code.

Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

1 files changed, 73 insertions, 55 deletions

diff --git a/arch/powerpc/kernel/traps.c b/arch/powerpc/kernel/traps.c
index 014f88f03d3f..c091527efd89 100644
--- a/arch/powerpc/kernel/traps.c
+++ b/arch/powerpc/kernel/traps.c
@@ -98,18 +98,14 @@ static void pmac_backlight_unblank(void)
 static inline void pmac_backlight_unblank(void) { }
 #endif
 
-int die(const char *str, struct pt_regs *regs, long err)
+static arch_spinlock_t die_lock = __ARCH_SPIN_LOCK_UNLOCKED;
+static int die_owner = -1;
+static unsigned int die_nest_count;
+static int die_counter;
+
+static unsigned __kprobes long oops_begin(struct pt_regs *regs)
 {
-        static struct {
-                raw_spinlock_t lock;
-                u32 lock_owner;
-                int lock_owner_depth;
-        } die = {
-                .lock =                 __RAW_SPIN_LOCK_UNLOCKED(die.lock),
-                .lock_owner =           -1,
-                .lock_owner_depth =     0
-        };
-        static int die_counter;
+        int cpu;
         unsigned long flags;
 
         if (debugger(regs))
@@ -117,50 +113,37 @@ int die(const char *str, struct pt_regs *regs, long err)
 
         oops_enter();
 
-        if (die.lock_owner != raw_smp_processor_id()) {
-                console_verbose();
-                raw_spin_lock_irqsave(&die.lock, flags);
-                die.lock_owner = smp_processor_id();
-                die.lock_owner_depth = 0;
-                bust_spinlocks(1);
-                if (machine_is(powermac))
-                        pmac_backlight_unblank();
-        } else {
-                local_save_flags(flags);
-        }
-
-        if (++die.lock_owner_depth < 3) {
-                printk("Oops: %s, sig: %ld [#%d]\n", str, err, ++die_counter);
-#ifdef CONFIG_PREEMPT
-                printk("PREEMPT ");
-#endif
-#ifdef CONFIG_SMP
-                printk("SMP NR_CPUS=%d ", NR_CPUS);
-#endif
-#ifdef CONFIG_DEBUG_PAGEALLOC
-                printk("DEBUG_PAGEALLOC ");
-#endif
-#ifdef CONFIG_NUMA
-                printk("NUMA ");
-#endif
-                printk("%s\n", ppc_md.name ? ppc_md.name : "");
-
-                if (notify_die(DIE_OOPS, str, regs, err, 255,
-                               SIGSEGV) == NOTIFY_STOP)
-                        return 1;
-
-                print_modules();
-                show_regs(regs);
-        } else {
-                printk("Recursive die() failure, output suppressed\n");
+        /* racy, but better than risking deadlock. */
+        raw_local_irq_save(flags);
+        cpu = smp_processor_id();
+        if (!arch_spin_trylock(&die_lock)) {
+                if (cpu == die_owner)
+                        /* nested oops. should stop eventually */;
+                else
+                        arch_spin_lock(&die_lock);
         }
+        die_nest_count++;
+        die_owner = cpu;
+        console_verbose();
+        bust_spinlocks(1);
+        if (machine_is(powermac))
+                pmac_backlight_unblank();
+        return flags;
+}
 
+static void __kprobes oops_end(unsigned long flags, struct pt_regs *regs,
+                               int signr)
+{
         bust_spinlocks(0);
-        die.lock_owner = -1;
+        die_owner = -1;
         add_taint(TAINT_DIE);
+        die_nest_count--;
         oops_exit();
         printk("\n");
-        raw_spin_unlock_irqrestore(&die.lock, flags);
+        if (!die_nest_count)
+                /* Nest count reaches zero, release the lock. */
+                arch_spin_unlock(&die_lock);
+        raw_local_irq_restore(flags);
 
         /*
          * A system reset (0x100) is a request to dump, so we always send
@@ -177,6 +160,9 @@ int die(const char *str, struct pt_regs *regs, long err)
                 crash_kexec_secondary(regs);
         }
 
+        if (!signr)
+                return;
+
         /*
          * While our oops output is serialised by a spinlock, output
          * from panic() called below can race and corrupt it. If we
@@ -190,15 +176,46 @@ int die(const char *str, struct pt_regs *regs, long err)
 
         if (in_interrupt())
                 panic("Fatal exception in interrupt");
-
         if (panic_on_oops)
                 panic("Fatal exception");
+        do_exit(signr);
+}
 
-        do_exit(err);
+static int __kprobes __die(const char *str, struct pt_regs *regs, long err)
+{
+        printk("Oops: %s, sig: %ld [#%d]\n", str, err, ++die_counter);
+#ifdef CONFIG_PREEMPT
+        printk("PREEMPT ");
+#endif
+#ifdef CONFIG_SMP
+        printk("SMP NR_CPUS=%d ", NR_CPUS);
+#endif
+#ifdef CONFIG_DEBUG_PAGEALLOC
+        printk("DEBUG_PAGEALLOC ");
+#endif
+#ifdef CONFIG_NUMA
+        printk("NUMA ");
+#endif
+        printk("%s\n", ppc_md.name ? ppc_md.name : "");
+
+        if (notify_die(DIE_OOPS, str, regs, err, 255, SIGSEGV) == NOTIFY_STOP)
+                return 1;
+
+        print_modules();
+        show_regs(regs);
 
         return 0;
 }
 
+void die(const char *str, struct pt_regs *regs, long err)
+{
+        unsigned long flags = oops_begin(regs);
+
+        if (__die(str, regs, err))
+                err = 0;
+        oops_end(flags, regs, err);
+}
+
 void user_single_step_siginfo(struct task_struct *tsk,
                                 struct pt_regs *regs, siginfo_t *info)
 {
@@ -217,10 +234,11 @@ void _exception(int signr, struct pt_regs *regs, int code, unsigned long addr)
                         "at %016lx nip %016lx lr %016lx code %x\n";
 
         if (!user_mode(regs)) {
-                if (die("Exception in kernel mode", regs, signr))
-                        return;
-        } else if (show_unhandled_signals &&
-                   unhandled_signal(current, signr)) {
+                die("Exception in kernel mode", regs, signr);
+                return;
+        }
+
+        if (show_unhandled_signals && unhandled_signal(current, signr)) {
                 printk_ratelimited(regs->msr & MSR_64BIT ? fmt64 : fmt32,
                                    current->comm, current->pid, signr,
                                    addr, regs->nip, regs->link, code);