Re: [PATCH v2 tip/core/rcu 02/18] lockdep: Make RCU suspicious-access splats use pr_err

Josh Triplett
2017-01-21T20:40:45Z

On Tue, Jan 17, 2017 at 06:53:41PM -0800, Paul E. McKenney wrote:
> This commit switches RCU suspicious-access splats use pr_err()
> instead of the current INFO printk()s. This change makes it easier
> to automatically classify splats.
>
> Reported-by: Dmitry Vyukov <dvyukov@google.com>
> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
> ---
> kernel/locking/lockdep.c | 12 ++++++------
> 1 file changed, 6 insertions(+), 6 deletions(-)
>
> diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
> index 7c38f8f3d97b..a74c0630172a 100644
> --- a/kernel/locking/lockdep.c
> +++ b/kernel/locking/lockdep.c
> @@ -4412,13 +4412,13 @@ void lockdep_rcu_suspicious(const char *file, const int line, const char *s)
> #endif /* #ifdef CONFIG_PROVE_RCU_REPEATEDLY */
> /* Note: the following can be executed concurrently, so be careful. */
> printk("\n");
> - printk("===============================\n");
> - printk("[ INFO: suspicious RCU usage. ]\n");
> + pr_err("===============================\n");
> + pr_err("[ suspicious RCU usage. ]\n");

While re-adding the square bracket makes it symmetric, this change still
seems odd, and unrelated to the switch to pr_err. You could change it
to "ERR:" if you want, if "INFO:" feels inaccurate to you.

> print_kernel_ident();
> - printk("-------------------------------\n");
> - printk("%s:%d %s!\n", file, line, s);
> - printk("\nother info that might help us debug this:\n\n");
> - printk("\n%srcu_scheduler_active = %d, debug_locks = %d\n",
> + pr_err("-------------------------------\n");
> + pr_err("%s:%d %s!\n", file, line, s);
> + pr_err("\nother info that might help us debug this:\n\n");
> + pr_err("\n%srcu_scheduler_active = %d, debug_locks = %d\n",
> !rcu_lockdep_current_cpu_online()
> ? "RCU used illegally from offline CPU!\n"
> : !rcu_is_watching()
> --
> 2.5.2
>