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sched_ext: Improve error reporting during loading

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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@kernel.org>
Cc: David Vernet <void@manifault.com>
Cc: Daniel Hodges <hodges.daniel.scott@gmail.com>
Cc: Changwoo Min <multics69@gmail.com>
Cc: Andrea Righi <andrea.righi@linux.dev>
Cc: Dan Schatzberg <schatzberg.dan@gmail.com>
This commit is contained in:
Tejun Heo 2024-10-02 10:33:37 -10:00
parent fcbc423577
commit cc9877fb76
1 changed files with 19 additions and 11 deletions
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30
kernel/sched/ext.c
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@ -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);
@ -4117,6 +4121,7 @@ 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;
@ -5041,6 +5046,7 @@ static int scx_ops_enable(struct sched_ext_ops *ops, struct bpf_link *link)
if (ret) {
ret = ops_sanitize_err("init", ret);
cpus_read_unlock();
scx_ops_error("ops.init() failed (%d)", ret);
goto err_disable;
}
}
@ -5150,8 +5156,8 @@ static int scx_ops_enable(struct sched_ext_ops *ops, struct bpf_link *link)
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;
}
@ -5199,14 +5205,8 @@ static int scx_ops_enable(struct sched_ext_ops *ops, struct bpf_link *link)
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;
}
@ -5241,10 +5241,18 @@ static int scx_ops_enable(struct sched_ext_ops *ops, struct bpf_link *link)
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;
}