tracing: x86, mmiotrace: only register for die notifier when tracer active

Follow up to afcfe024aebd74b0984a41af9a34e009cf5badaf in Linus' tree
("x86: mmiotrace: quieten spurious warning message")

Signed-off-by: Stuart Bennett <stuart@freedesktop.org>
Acked-by: Pekka Paalanen <pq@iki.fi>
Cc: Steven Rostedt <rostedt@goodmis.org>
LKML-Reference: <1240946271-7083-5-git-send-email-stuart@freedesktop.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

2 files changed, 24 insertions, 5 deletions

diff --git a/arch/x86/mm/kmmio.c b/arch/x86/mm/kmmio.c
index a769d1a2d93b..256ce643b0ba 100644
--- a/arch/x86/mm/kmmio.c
+++ b/arch/x86/mm/kmmio.c
@@ -311,7 +311,12 @@ static int post_kmmio_handler(unsigned long condition, struct pt_regs *regs)
         struct kmmio_context *ctx = &get_cpu_var(kmmio_ctx);
 
         if (!ctx->active) {
-                pr_debug("kmmio: spurious debug trap on CPU %d.\n",
+                /*
+                 * debug traps without an active context are due to either
+                 * something external causing them (f.e. using a debugger while
+                 * mmio tracing enabled), or erroneous behaviour
+                 */
+                pr_warning("kmmio: unexpected debug trap on CPU %d.\n",
                                                         smp_processor_id());
                 goto out;
         }
@@ -529,8 +534,8 @@ void unregister_kmmio_probe(struct kmmio_probe *p)
 }
 EXPORT_SYMBOL(unregister_kmmio_probe);
 
-static int kmmio_die_notifier(struct notifier_block *nb, unsigned long val,
-                                                                void *args)
+static int
+kmmio_die_notifier(struct notifier_block *nb, unsigned long val, void *args)
 {
         struct die_args *arg = args;
 
@@ -545,11 +550,23 @@ static struct notifier_block nb_die = {
         .notifier_call = kmmio_die_notifier
 };
 
-static int __init init_kmmio(void)
+int kmmio_init(void)
 {
         int i;
+
         for (i = 0; i < KMMIO_PAGE_TABLE_SIZE; i++)
                 INIT_LIST_HEAD(&kmmio_page_table[i]);
+
         return register_die_notifier(&nb_die);
 }
-fs_initcall(init_kmmio); /* should be before device_initcall() */
+
+void kmmio_cleanup(void)
+{
+        int i;
+
+        unregister_die_notifier(&nb_die);
+        for (i = 0; i < KMMIO_PAGE_TABLE_SIZE; i++) {
+                WARN_ONCE(!list_empty(&kmmio_page_table[i]),
+                        KERN_ERR "kmmio_page_table not empty at cleanup, any further tracing will leak memory.\n");
+        }
+}
diff --git a/arch/x86/mm/mmio-mod.c b/arch/x86/mm/mmio-mod.c
index c9342ed8b402..132772a8ec57 100644
--- a/arch/x86/mm/mmio-mod.c
+++ b/arch/x86/mm/mmio-mod.c
@@ -451,6 +451,7 @@ void enable_mmiotrace(void)
 
         if (nommiotrace)
                 pr_info(NAME "MMIO tracing disabled.\n");
+        kmmio_init();
         enter_uniprocessor();
         spin_lock_irq(&trace_lock);
         atomic_inc(&mmiotrace_enabled);
@@ -473,6 +474,7 @@ void disable_mmiotrace(void)
 
         clear_trace_list(); /* guarantees: no more kmmio callbacks */
         leave_uniprocessor();
+        kmmio_cleanup();
         pr_info(NAME "disabled.\n");
 out:
         mutex_unlock(&mmiotrace_mutex);