Re: [PATCH v2 03/14] notifiers: Assert that RCU is watching in notify_die
From: Borislav Petkov
Date: Mon Jun 22 2015 - 07:37:31 EST
On Thu, Jun 18, 2015 at 12:08:35PM -0700, Andy Lutomirski wrote:
> Low-level arch entries often call notify_die, and it's easy for arch
> code to fail to exit an RCU quiescent state first. Assert that
> we're not quiescent in notify_die.
> Signed-off-by: Andy Lutomirski <luto@xxxxxxxxxx>
> kernel/notifier.c | 2 ++
> 1 file changed, 2 insertions(+)
> diff --git a/kernel/notifier.c b/kernel/notifier.c
> index ae9fc7cc360e..980e4330fb59 100644
> --- a/kernel/notifier.c
> +++ b/kernel/notifier.c
> @@ -544,6 +544,8 @@ int notrace notify_die(enum die_val val, const char *str,
> .signr = sig,
> + rcu_lockdep_assert(rcu_is_watching(),
> + "notify_die called but RCU thinks we're quiescent");
> return atomic_notifier_call_chain(&die_chain, val, &args);
Ok, we're about to die and we will prepend what would be a more
important splat possibly hinting at the problem is with a lockdep splat.
I think we should do the assertion and make the rcu_lockdep splat come
last I but don't see how to do this easily from all the notify_die()
Or am I missing something...?
ECO tip #101: Trim your mails when you reply.
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