Re: [PATCH sched_ext/for-6.12] sched_ext: Improve logging around enable/disable

[David Vernet <void@manifault.com>]

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On Wed, Aug 07, 2024 at 02:52:50PM -1000, Tejun Heo wrote:

Hi Tejun,

> sched_ext currently doesn't generate messages when the BPF scheduler is
> enabled and disabled unless there are errors. It is useful to have paper
> trail. Improve logging around enable/disable:
> 
> - Generate info messages on enable and non-error disable.
> 
> - Update error exit message formatting so that it's consistent with
>   non-error message. Also, prefix ei->msg with the BPF scheduler's name to
>   make it clear where the message is coming from.
> 
> - Shorten scx_exit_reason() strings for SCX_EXIT_UNREG* for brevity and
>   consistency.
> 
> Signed-off-by: Tejun Heo <tj@kernel.org>
> Suggested-by: Phil Auld <pauld@redhat.com>
> ---
>  kernel/sched/ext.c |   21 +++++++++++++--------
>  1 file changed, 13 insertions(+), 8 deletions(-)
> 
> diff --git a/kernel/sched/ext.c b/kernel/sched/ext.c
> index 60a7eb7d8a9e..eea2fda8e099 100644
> --- a/kernel/sched/ext.c
> +++ b/kernel/sched/ext.c
> @@ -4004,11 +4004,11 @@ static const char *scx_exit_reason(enum scx_exit_kind kind)
>  {
>  	switch (kind) {
>  	case SCX_EXIT_UNREG:
> -		return "Scheduler unregistered from user space";
> +		return "unregistered from user space";
>  	case SCX_EXIT_UNREG_BPF:
> -		return "Scheduler unregistered from BPF";
> +		return "unregistered from BPF";
>  	case SCX_EXIT_UNREG_KERN:
> -		return "Scheduler unregistered from the main kernel";
> +		return "unregistered from the main kernel";
>  	case SCX_EXIT_SYSRQ:
>  		return "disabled by sysrq-S";
>  	case SCX_EXIT_ERROR:
> @@ -4126,14 +4126,17 @@ static void scx_ops_disable_workfn(struct kthread_work *work)
>  	percpu_up_write(&scx_fork_rwsem);
>  
>  	if (ei->kind >= SCX_EXIT_ERROR) {
> -		printk(KERN_ERR "sched_ext: BPF scheduler \"%s\" errored, disabling\n", scx_ops.name);
> +		pr_err("sched_ext: BPF scheduler \"%s\" disabled (%s)\n",
> +		       scx_ops.name, ei->reason);
>  
> -		if (ei->msg[0] == '\0')
> -			printk(KERN_ERR "sched_ext: %s\n", ei->reason);
> -		else
> -			printk(KERN_ERR "sched_ext: %s (%s)\n", ei->reason, ei->msg);
> +		if (ei->msg[0] != '\0')
> +			printk(KERN_ERR "sched_ext: %s: %s\n",
> +			       scx_ops.name, ei->msg);

Was it intentional to use pr_err() above, and printk() here? If not,
let's make them consistent?

Looks good otherwise.

Acked-by: David Vernet <void@manifault.com>

Thanks,
David

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