netdev - Re: [PATCH net-next] net: ethernet: mtk_wed: fix sleep while atomic in mtk_wed_wo_queue

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Message-ID: <CALs4sv0fjaaYf-s6b_ArT2U8=0ySLUZEwvgM2rZ-f1F8ap3+fg@mail.gmail.com>
Date:   Fri, 2 Dec 2022 13:37:38 +0530
From:   Pavan Chebbi <pavan.chebbi@...adcom.com>
To:     Lorenzo Bianconi <lorenzo@...nel.org>
Cc:     netdev@...r.kernel.org, nbd@....name, john@...ozen.org,
        sean.wang@...iatek.com, Mark-MC.Lee@...iatek.com,
        davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
        pabeni@...hat.com, matthias.bgg@...il.com,
        linux-mediatek@...ts.infradead.org, lorenzo.bianconi@...hat.com
Subject: Re: [PATCH net-next] net: ethernet: mtk_wed: fix sleep while atomic
 in mtk_wed_wo_queue_refill

On Thu, Dec 1, 2022 at 8:57 PM Lorenzo Bianconi <lorenzo@...nel.org> wrote:
>
> In order to fix the following sleep while atomic bug always alloc pages
> with GFP_ATOMIC in mtk_wed_wo_queue_refill since page_frag_alloc runs in
> spin_lock critical section.
>
> [    9.049719] Hardware name: MediaTek MT7986a RFB (DT)
> [    9.054665] Call trace:
> [    9.057096]  dump_backtrace+0x0/0x154
> [    9.060751]  show_stack+0x14/0x1c
> [    9.064052]  dump_stack_lvl+0x64/0x7c
> [    9.067702]  dump_stack+0x14/0x2c
> [    9.071001]  ___might_sleep+0xec/0x120
> [    9.074736]  __might_sleep+0x4c/0x9c
> [    9.078296]  __alloc_pages+0x184/0x2e4
> [    9.082030]  page_frag_alloc_align+0x98/0x1ac
> [    9.086369]  mtk_wed_wo_queue_refill+0x134/0x234
> [    9.090974]  mtk_wed_wo_init+0x174/0x2c0
> [    9.094881]  mtk_wed_attach+0x7c8/0x7e0
> [    9.098701]  mt7915_mmio_wed_init+0x1f0/0x3a0 [mt7915e]
> [    9.103940]  mt7915_pci_probe+0xec/0x3bc [mt7915e]
> [    9.108727]  pci_device_probe+0xac/0x13c
> [    9.112638]  really_probe.part.0+0x98/0x2f4
> [    9.116807]  __driver_probe_device+0x94/0x13c
> [    9.121147]  driver_probe_device+0x40/0x114
> [    9.125314]  __driver_attach+0x7c/0x180
> [    9.129133]  bus_for_each_dev+0x5c/0x90
> [    9.132953]  driver_attach+0x20/0x2c
> [    9.136513]  bus_add_driver+0x104/0x1fc
> [    9.140333]  driver_register+0x74/0x120
> [    9.144153]  __pci_register_driver+0x40/0x50
> [    9.148407]  mt7915_init+0x5c/0x1000 [mt7915e]
> [    9.152848]  do_one_initcall+0x40/0x25c
> [    9.156669]  do_init_module+0x44/0x230
> [    9.160403]  load_module+0x1f30/0x2750
> [    9.164135]  __do_sys_init_module+0x150/0x200
> [    9.168475]  __arm64_sys_init_module+0x18/0x20
> [    9.172901]  invoke_syscall.constprop.0+0x4c/0xe0
> [    9.177589]  do_el0_svc+0x48/0xe0
> [    9.180889]  el0_svc+0x14/0x50
> [    9.183929]  el0t_64_sync_handler+0x9c/0x120
> [    9.188183]  el0t_64_sync+0x158/0x15c
>
> Fixes: 799684448e3e ("net: ethernet: mtk_wed: introduce wed wo support")
> Signed-off-by: Lorenzo Bianconi <lorenzo@...nel.org>
> ---

Looks OK to me.
Reviewed-by: Pavan Chebbi <pavan.chebbi@...adcom.com>

>  drivers/net/ethernet/mediatek/mtk_wed_wo.c | 11 ++++++-----
>  1 file changed, 6 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/net/ethernet/mediatek/mtk_wed_wo.c b/drivers/net/ethernet/mediatek/mtk_wed_wo.c
> index 4754b6db009e..a219da85f4db 100644
> --- a/drivers/net/ethernet/mediatek/mtk_wed_wo.c
> +++ b/drivers/net/ethernet/mediatek/mtk_wed_wo.c
> @@ -133,17 +133,18 @@ mtk_wed_wo_dequeue(struct mtk_wed_wo *wo, struct mtk_wed_wo_queue *q, u32 *len,
>
>  static int
>  mtk_wed_wo_queue_refill(struct mtk_wed_wo *wo, struct mtk_wed_wo_queue *q,
> -                       gfp_t gfp, bool rx)
> +                       bool rx)
>  {
>         enum dma_data_direction dir = rx ? DMA_FROM_DEVICE : DMA_TO_DEVICE;
>         int n_buf = 0;
>
>         spin_lock_bh(&q->lock);
>         while (q->queued < q->n_desc) {
> -               void *buf = page_frag_alloc(&q->cache, q->buf_size, gfp);
>                 struct mtk_wed_wo_queue_entry *entry;
>                 dma_addr_t addr;
> +               void *buf;
>
> +               buf = page_frag_alloc(&q->cache, q->buf_size, GFP_ATOMIC);
>                 if (!buf)
>                         break;
>
> @@ -215,7 +216,7 @@ mtk_wed_wo_rx_run_queue(struct mtk_wed_wo *wo, struct mtk_wed_wo_queue *q)
>                         mtk_wed_mcu_rx_unsolicited_event(wo, skb);
>         }
>
> -       if (mtk_wed_wo_queue_refill(wo, q, GFP_ATOMIC, true)) {
> +       if (mtk_wed_wo_queue_refill(wo, q, true)) {
>                 u32 index = (q->head - 1) % q->n_desc;
>
>                 mtk_wed_wo_queue_kick(wo, q, index);
> @@ -432,7 +433,7 @@ mtk_wed_wo_hardware_init(struct mtk_wed_wo *wo)
>         if (ret)
>                 goto error;
>
> -       mtk_wed_wo_queue_refill(wo, &wo->q_tx, GFP_KERNEL, false);
> +       mtk_wed_wo_queue_refill(wo, &wo->q_tx, false);
>         mtk_wed_wo_queue_reset(wo, &wo->q_tx);
>
>         regs.desc_base = MTK_WED_WO_CCIF_DUMMY5;
> @@ -446,7 +447,7 @@ mtk_wed_wo_hardware_init(struct mtk_wed_wo *wo)
>         if (ret)
>                 goto error;
>
> -       mtk_wed_wo_queue_refill(wo, &wo->q_rx, GFP_KERNEL, true);
> +       mtk_wed_wo_queue_refill(wo, &wo->q_rx, true);
>         mtk_wed_wo_queue_reset(wo, &wo->q_rx);
>
>         /* rx queue irqmask */
> --
> 2.38.1
>

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