Subject: Re: [PATCH v2 1/1] qed: Fix scheduling in a tasklet while getting stats

From: Simon Horman <[email-masked]>
Date: Sat, 29 Jul 2023 13:07:38 +0200

On Thu, Jul 27, 2023 at 06:26:09PM +0300, Konstantin Khorenko wrote:
> Here we've got to a situation when tasklet called usleep_range() in PTT
> acquire logic, thus welcome to the "scheduling while atomic" BUG().
> 
>   BUG: scheduling while atomic: swapper/24/0/0x00000100
> 
>    [<ffffffffb41c6199>] schedule+0x29/0x70
>    [<ffffffffb41c5512>] schedule_hrtimeout_range_clock+0xb2/0x150
>    [<ffffffffb41c55c3>] schedule_hrtimeout_range+0x13/0x20
>    [<ffffffffb41c3bcf>] usleep_range+0x4f/0x70
>    [<ffffffffc08d3e58>] qed_ptt_acquire+0x38/0x100 [qed]
>    [<ffffffffc08eac48>] _qed_get_vport_stats+0x458/0x580 [qed]
>    [<ffffffffc08ead8c>] qed_get_vport_stats+0x1c/0xd0 [qed]
>    [<ffffffffc08dffd3>] qed_get_protocol_stats+0x93/0x100 [qed]
>                         qed_mcp_send_protocol_stats
>             case MFW_DRV_MSG_GET_LAN_STATS:
>             case MFW_DRV_MSG_GET_FCOE_STATS:
>             case MFW_DRV_MSG_GET_ISCSI_STATS:
>             case MFW_DRV_MSG_GET_RDMA_STATS:
>    [<ffffffffc08e36d8>] qed_mcp_handle_events+0x2d8/0x890 [qed]
>                         qed_int_assertion
>                         qed_int_attentions
>    [<ffffffffc08d9490>] qed_int_sp_dpc+0xa50/0xdc0 [qed]
>    [<ffffffffb3aa7623>] tasklet_action+0x83/0x140
>    [<ffffffffb41d9125>] __do_softirq+0x125/0x2bb
>    [<ffffffffb41d560c>] call_softirq+0x1c/0x30
>    [<ffffffffb3a30645>] do_softirq+0x65/0xa0
>    [<ffffffffb3aa78d5>] irq_exit+0x105/0x110
>    [<ffffffffb41d8996>] do_IRQ+0x56/0xf0
> 
> Fix this by making caller to provide the context whether it could be in
> atomic context flow or not when getting stats from QED driver.
> QED driver based on the context provided decide to schedule out or not
> when acquiring the PTT BAR window.
> 
> We faced the BUG_ON() while getting vport stats, but according to the
> code same issue could happen for fcoe and iscsi statistics as well, so
> fixing them too.
> 
> Fixes: 6c75424612a7 ("qed: Add support for NCSI statistics.")
> Fixes: 1e128c81290a ("qed: Add support for hardware offloaded FCoE.")
> Fixes: 2f2b2614e893 ("qed: Provide iSCSI statistics to management")
> Cc: Sudarsana Kalluru <[email-masked]>
> Cc: David Miller <[email-masked]>
> Cc: Manish Chopra <[email-masked]>
> 

nit: no blank line here.

> Signed-off-by: Konstantin Khorenko <[email-masked]>

Reviewed-by: Simon Horman <[email-masked]>