sched_ext: Improve logging around enable/disable

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.

v2: Use pr_*() instead of KERN_* consistently. (David)

Signed-off-by: Tejun Heo <tj@kernel.org>
Suggested-by: Phil Auld <pauld@redhat.com>
Reviewed-by: Phil Auld <pauld@redhat.com>
Acked-by: David Vernet <void@manifault.com>

diff --git a/kernel/sched/ext.c b/kernel/sched/ext.c
index 17af9c46d8914a7fefeb46e6df501daf6c8ba3a1..143c4207a8264409e1cc18343aff5320604dc1cf 100644 (file)
--- a/kernel/sched/ext.c
+++ b/kernel/sched/ext.c
@@ -4013,11 +4013,11 @@ 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:
@@ -4135,14 +4135,16 @@ 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')
+                       pr_err("sched_ext: %s: %s\n", scx_ops.name, ei->msg);
 
                stack_trace_print(ei->bt, ei->bt_len, 2);
+       } else {
+               pr_info("sched_ext: BPF scheduler \"%s\" disabled (%s)\n",
+                       scx_ops.name, ei->reason);
        }
 
        if (scx_ops.exit)
@@ -4817,6 +4819,8 @@ static int scx_ops_enable(struct sched_ext_ops *ops, struct bpf_link *link)
        if (!(ops->flags & SCX_OPS_SWITCH_PARTIAL))
                static_branch_enable(&__scx_switched_all);
 
+       pr_info("sched_ext: BPF scheduler \"%s\" enabled%s\n",
+               scx_ops.name, scx_switched_all() ? "" : " (partial)");
        kobject_uevent(scx_root_kobj, KOBJ_ADD);
        mutex_unlock(&scx_ops_enable_mutex);