On Thu, Aug 21, 2025 at 9:26 AM Kumar Kartikeya Dwivedi
<memxor@xxxxxxxxx> wrote:
>
> We noticed potential lock ups and delays in progs running in NMI context
> with the rqspinlock changes, which suggests more improvements need to be
> made before we can support ring buffer updates in such a context safely.
> Revert the change for now.
>
> Reported-by: Josef Bacik <josef@xxxxxxxxxxxxxx>
> Cc: stable@xxxxxxxxxxxxxxx
> Fixes: a650d38915c1 ("bpf: Convert ringbuf map to rqspinlock")
> Signed-off-by: Kumar Kartikeya Dwivedi <memxor@xxxxxxxxx>
> ---
> kernel/bpf/ringbuf.c | 17 ++++++++++-------
> 1 file changed, 10 insertions(+), 7 deletions(-)
>
patch bot seems to be ignoring this patch, it was applied to bpf tree, thanks!
> diff --git a/kernel/bpf/ringbuf.c b/kernel/bpf/ringbuf.c
> index 719d73299397..1499d8caa9a3 100644
> --- a/kernel/bpf/ringbuf.c
> +++ b/kernel/bpf/ringbuf.c
> @@ -11,7 +11,6 @@
> #include <linux/kmemleak.h>
> #include <uapi/linux/btf.h>
> #include <linux/btf_ids.h>
> -#include <asm/rqspinlock.h>
>
> #define RINGBUF_CREATE_FLAG_MASK (BPF_F_NUMA_NODE)
>
> @@ -30,7 +29,7 @@ struct bpf_ringbuf {
> u64 mask;
> struct page **pages;
> int nr_pages;
> - rqspinlock_t spinlock ____cacheline_aligned_in_smp;
> + raw_spinlock_t spinlock ____cacheline_aligned_in_smp;
> /* For user-space producer ring buffers, an atomic_t busy bit is used
> * to synchronize access to the ring buffers in the kernel, rather than
> * the spinlock that is used for kernel-producer ring buffers. This is
> @@ -174,7 +173,7 @@ static struct bpf_ringbuf *bpf_ringbuf_alloc(size_t data_sz, int numa_node)
> if (!rb)
> return NULL;
>
> - raw_res_spin_lock_init(&rb->spinlock);
> + raw_spin_lock_init(&rb->spinlock);
> atomic_set(&rb->busy, 0);
> init_waitqueue_head(&rb->waitq);
> init_irq_work(&rb->work, bpf_ringbuf_notify);
> @@ -417,8 +416,12 @@ static void *__bpf_ringbuf_reserve(struct bpf_ringbuf *rb, u64 size)
>
> cons_pos = smp_load_acquire(&rb->consumer_pos);
>
> - if (raw_res_spin_lock_irqsave(&rb->spinlock, flags))
> - return NULL;
> + if (in_nmi()) {
> + if (!raw_spin_trylock_irqsave(&rb->spinlock, flags))
> + return NULL;
> + } else {
> + raw_spin_lock_irqsave(&rb->spinlock, flags);
> + }
>
> pend_pos = rb->pending_pos;
> prod_pos = rb->producer_pos;
> @@ -443,7 +446,7 @@ static void *__bpf_ringbuf_reserve(struct bpf_ringbuf *rb, u64 size)
> */
> if (new_prod_pos - cons_pos > rb->mask ||
> new_prod_pos - pend_pos > rb->mask) {
> - raw_res_spin_unlock_irqrestore(&rb->spinlock, flags);
> + raw_spin_unlock_irqrestore(&rb->spinlock, flags);
> return NULL;
> }
>
> @@ -455,7 +458,7 @@ static void *__bpf_ringbuf_reserve(struct bpf_ringbuf *rb, u64 size)
> /* pairs with consumer's smp_load_acquire() */
> smp_store_release(&rb->producer_pos, new_prod_pos);
>
> - raw_res_spin_unlock_irqrestore(&rb->spinlock, flags);
> + raw_spin_unlock_irqrestore(&rb->spinlock, flags);
>
> return (void *)hdr + BPF_RINGBUF_HDR_SZ;
> }
> --
> 2.50.0
>
