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>

diff --git a/arch/x86/mm/kmmio.c b/arch/x86/mm/kmmio.c
index a769d1a..256ce64 100644 (file)
--- 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 c9342ed..132772a 100644 (file)
--- 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);

diff --git a/include/linux/mmiotrace.h b/include/linux/mmiotrace.h
index 3d1b7bd..97491f7 100644 (file)
--- a/include/linux/mmiotrace.h
+++ b/include/linux/mmiotrace.h
@@ -30,6 +30,8 @@ extern unsigned int kmmio_count;
 
 extern int register_kmmio_probe(struct kmmio_probe *p);
 extern void unregister_kmmio_probe(struct kmmio_probe *p);
+extern int kmmio_init(void);
+extern void kmmio_cleanup(void);
 
 #ifdef CONFIG_MMIOTRACE
 /* kmmio is active by some kmmio_probes? */