[PATCH] sched_ext: Improve logging around enable/disable

From: Tejun Heo
Date: Wed Aug 07 2024 - 20:52:50 EST


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@xxxxxxxxxx>
Suggested-by: Phil Auld <pauld@xxxxxxxxxx>
Reviewed-by: Phil Auld <pauld@xxxxxxxxxx>
Acked-by: David Vernet <void@xxxxxxxxxxxxx>
---

Applied to sched_ext/for-6.12 w/ the pr_err() update.

Thanks.

kernel/sched/ext.c | 20 ++++++++++++--------
1 file changed, 12 insertions(+), 8 deletions(-)

diff --git a/kernel/sched/ext.c b/kernel/sched/ext.c
index 17af9c46d891..143c4207a826 100644
--- 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);

--
2.46.0