On Tue, Jul 1, 2025 at 11:17 PM Kumar Kartikeya Dwivedi
<memxor@xxxxxxxxx> wrote:
>
> Begin reporting rqspinlock deadlocks and timeout to BPF program's
> stderr.
>
> Signed-off-by: Kumar Kartikeya Dwivedi <memxor@xxxxxxxxx>
> ---
> kernel/bpf/rqspinlock.c | 23 +++++++++++++++++++++++
> 1 file changed, 23 insertions(+)
>
Reviewed-by: Emil Tsalapatis <emil@xxxxxxxxxxxxxxx>
> diff --git a/kernel/bpf/rqspinlock.c b/kernel/bpf/rqspinlock.c
> index 338305c8852c..5ab354d55d82 100644
> --- a/kernel/bpf/rqspinlock.c
> +++ b/kernel/bpf/rqspinlock.c
> @@ -666,6 +666,27 @@ EXPORT_SYMBOL_GPL(resilient_queued_spin_lock_slowpath);
>
> __bpf_kfunc_start_defs();
>
> +static void bpf_prog_report_rqspinlock_violation(const char *str, void *lock, bool irqsave)
> +{
> + struct rqspinlock_held *rqh = this_cpu_ptr(&rqspinlock_held_locks);
> + struct bpf_stream_stage ss;
> + struct bpf_prog *prog;
> +
> + prog = bpf_prog_find_from_stack();
> + if (!prog)
> + return;
> + bpf_stream_stage(ss, prog, BPF_STDERR, ({
> + bpf_stream_printk(ss, "ERROR: %s for bpf_res_spin_lock%s\n", str, irqsave ? "_irqsave" : "");
> + bpf_stream_printk(ss, "Attempted lock = 0x%px\n", lock);
> + bpf_stream_printk(ss, "Total held locks = %d\n", rqh->cnt);
> + for (int i = 0; i < min(RES_NR_HELD, rqh->cnt); i++)
> + bpf_stream_printk(ss, "Held lock[%2d] = 0x%px\n", i, rqh->locks[i]);
> + bpf_stream_dump_stack(ss);
> + }));
> +}
> +
> +#define REPORT_STR(ret) ({ (ret) == -ETIMEDOUT ? "Timeout detected" : "AA or ABBA deadlock detected"; })
> +
> __bpf_kfunc int bpf_res_spin_lock(struct bpf_res_spin_lock *lock)
> {
> int ret;
> @@ -676,6 +697,7 @@ __bpf_kfunc int bpf_res_spin_lock(struct bpf_res_spin_lock *lock)
> preempt_disable();
> ret = res_spin_lock((rqspinlock_t *)lock);
> if (unlikely(ret)) {
> + bpf_prog_report_rqspinlock_violation(REPORT_STR(ret), lock, false);
> preempt_enable();
> return ret;
> }
> @@ -698,6 +720,7 @@ __bpf_kfunc int bpf_res_spin_lock_irqsave(struct bpf_res_spin_lock *lock, unsign
> local_irq_save(flags);
> ret = res_spin_lock((rqspinlock_t *)lock);
> if (unlikely(ret)) {
> + bpf_prog_report_rqspinlock_violation(REPORT_STR(ret), lock, true);
> local_irq_restore(flags);
> preempt_enable();
> return ret;
> --
> 2.47.1
>
