[PATCH sched_ext/for-6.12-fixes] sched_ext: Improve error reporting during loading
From: Tejun Heo
Date: Wed Oct 02 2024 - 16:33:50 EST
When the BPF scheduler fails, ops.exit() allows rich error reporting through
scx_exit_info. Use scx.exit() path consistently for all failures which can
be caused by the BPF scheduler:
- scx_ops_error() is called after ops.init() and ops.cgroup_init() failure
to record error information.
- ops.init_task() failure now uses scx_ops_error() instead of pr_err().
- The err_disable path updated to automatically trigger scx_ops_error() to
cover cases that the error message hasn't already been generated and
always return 0 indicating init success so that the error is reported
through ops.exit().
Signed-off-by: Tejun Heo <tj@xxxxxxxxxx>
Cc: David Vernet <void@xxxxxxxxxxxxx>
Cc: Daniel Hodges <hodges.daniel.scott@xxxxxxxxx>
Cc: Changwoo Min <multics69@xxxxxxxxx>
Cc: Andrea Righi <andrea.righi@xxxxxxxxx>
Cc: Dan Schatzberg <schatzberg.dan@xxxxxxxxx>
---
kernel/sched/ext.c | 30 +++++++++++++++++++-----------
1 file changed, 19 insertions(+), 11 deletions(-)
--- a/kernel/sched/ext.c
+++ b/kernel/sched/ext.c
@@ -625,6 +625,10 @@ struct sched_ext_ops {
/**
* exit - Clean up after the BPF scheduler
* @info: Exit info
+ *
+ * ops.exit() is also called on ops.init() failure, which is a bit
+ * unusual. This is to allow rich reporting through @info on how
+ * ops.init() failed.
*/
void (*exit)(struct scx_exit_info *info);
@@ -4184,6 +4188,7 @@ static int scx_cgroup_init(void)
css->cgroup, &args);
if (ret) {
css_put(css);
+ scx_ops_error("ops.cgroup_init() failed (%d)", ret);
return ret;
}
tg->scx_flags |= SCX_TG_INITED;
@@ -5108,6 +5113,7 @@ static int scx_ops_enable(struct sched_e
if (ret) {
ret = ops_sanitize_err("init", ret);
cpus_read_unlock();
+ scx_ops_error("ops.init() failed (%d)", ret);
goto err_disable;
}
}
@@ -5217,8 +5223,8 @@ static int scx_ops_enable(struct sched_e
spin_lock_irq(&scx_tasks_lock);
scx_task_iter_exit(&sti);
spin_unlock_irq(&scx_tasks_lock);
- pr_err("sched_ext: ops.init_task() failed (%d) for %s[%d] while loading\n",
- ret, p->comm, p->pid);
+ scx_ops_error("ops.init_task() failed (%d) for %s[%d]",
+ ret, p->comm, p->pid);
goto err_disable_unlock_all;
}
@@ -5266,14 +5272,8 @@ static int scx_ops_enable(struct sched_e
scx_ops_bypass(false);
- /*
- * Returning an error code here would lose the recorded error
- * information. Exit indicating success so that the error is notified
- * through ops.exit() with all the details.
- */
if (!scx_ops_tryset_enable_state(SCX_OPS_ENABLED, SCX_OPS_ENABLING)) {
WARN_ON_ONCE(atomic_read(&scx_exit_kind) == SCX_EXIT_NONE);
- ret = 0;
goto err_disable;
}
@@ -5308,10 +5308,18 @@ err_disable_unlock_all:
scx_ops_bypass(false);
err_disable:
mutex_unlock(&scx_ops_enable_mutex);
- /* must be fully disabled before returning */
- scx_ops_disable(SCX_EXIT_ERROR);
+ /*
+ * Returning an error code here would not pass all the error information
+ * to userspace. Record errno using scx_ops_error() for cases
+ * scx_ops_error() wasn't already invoked and exit indicating success so
+ * that the error is notified through ops.exit() with all the details.
+ *
+ * Flush scx_ops_disable_work to ensure that error is reported before
+ * init completion.
+ */
+ scx_ops_error("scx_ops_enable() failed (%d)", ret);
kthread_flush_work(&scx_ops_disable_work);
- return ret;
+ return 0;
}