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SubjectRe: [PATCH] x86 mmiotrace: only register for die notifier when tracer active

* Stuart Bennett <stuart@freedesktop.org> wrote:

> 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>
> ---
> arch/x86/mm/kmmio.c | 21 ++++++++++++++++++---
> arch/x86/mm/mmio-mod.c | 2 ++
> include/linux/mmiotrace.h | 2 ++
> 3 files changed, 22 insertions(+), 3 deletions(-)
>
> diff --git a/arch/x86/mm/kmmio.c b/arch/x86/mm/kmmio.c
> index 422f49e..bdbbf0d 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;
> }
> @@ -545,11 +550,21 @@ 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");
> +}

Note, i cleaned this up a bit in the commit i applied - we rather
let strings become over-long than break them in the middle

Ingo


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