netdev - Re: [PATCH iwl-net] idpf: convert control queue mutex to a spinlock

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Message-ID: <20250528095521.GZ365796@horms.kernel.org>
Date: Wed, 28 May 2025 10:55:21 +0100
From: Simon Horman <horms@...nel.org>
To: Ahmed Zaki <ahmed.zaki@...el.com>
Cc: intel-wired-lan@...ts.osuosl.org, netdev@...r.kernel.org,
	Aleksandr Loktionov <aleksandr.loktionov@...el.com>
Subject: Re: [PATCH iwl-net] idpf: convert control queue mutex to a spinlock

On Fri, May 23, 2025 at 02:55:37PM -0600, Ahmed Zaki wrote:
> With VIRTCHNL2_CAP_MACFILTER enabled, the following warning is generated
> on module load:
> 
> [  324.701677] BUG: sleeping function called from invalid context at kernel/locking/mutex.c:578
> [  324.701684] in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 1582, name: NetworkManager
> [  324.701689] preempt_count: 201, expected: 0
> [  324.701693] RCU nest depth: 0, expected: 0
> [  324.701697] 2 locks held by NetworkManager/1582:
> [  324.701702]  #0: ffffffff9f7be770 (rtnl_mutex){....}-{3:3}, at: rtnl_newlink+0x791/0x21e0
> [  324.701730]  #1: ff1100216c380368 (_xmit_ETHER){....}-{2:2}, at: __dev_open+0x3f0/0x870
> [  324.701749] Preemption disabled at:
> [  324.701752] [<ffffffff9cd23b9d>] __dev_open+0x3dd/0x870
> [  324.701765] CPU: 30 UID: 0 PID: 1582 Comm: NetworkManager Not tainted 6.15.0-rc5+ #2 PREEMPT(voluntary)
> [  324.701771] Hardware name: Intel Corporation M50FCP2SBSTD/M50FCP2SBSTD, BIOS SE5C741.86B.01.01.0001.2211140926 11/14/2022
> [  324.701774] Call Trace:
> [  324.701777]  <TASK>
> [  324.701779]  dump_stack_lvl+0x5d/0x80
> [  324.701788]  ? __dev_open+0x3dd/0x870
> [  324.701793]  __might_resched.cold+0x1ef/0x23d
> <..>
> [  324.701818]  __mutex_lock+0x113/0x1b80
> <..>
> [  324.701917]  idpf_ctlq_clean_sq+0xad/0x4b0 [idpf]
> [  324.701935]  ? kasan_save_track+0x14/0x30
> [  324.701941]  idpf_mb_clean+0x143/0x380 [idpf]
> <..>
> [  324.701991]  idpf_send_mb_msg+0x111/0x720 [idpf]
> [  324.702009]  idpf_vc_xn_exec+0x4cc/0x990 [idpf]
> [  324.702021]  ? rcu_is_watching+0x12/0xc0
> [  324.702035]  idpf_add_del_mac_filters+0x3ed/0xb50 [idpf]
> <..>
> [  324.702122]  __hw_addr_sync_dev+0x1cf/0x300
> [  324.702126]  ? find_held_lock+0x32/0x90
> [  324.702134]  idpf_set_rx_mode+0x317/0x390 [idpf]
> [  324.702152]  __dev_open+0x3f8/0x870
> [  324.702159]  ? __pfx___dev_open+0x10/0x10
> [  324.702174]  __dev_change_flags+0x443/0x650
> <..>
> [  324.702208]  netif_change_flags+0x80/0x160
> [  324.702218]  do_setlink.isra.0+0x16a0/0x3960
> <..>
> [  324.702349]  rtnl_newlink+0x12fd/0x21e0
> 
> The sequence is as follows:
> 	rtnl_newlink()->
> 	__dev_change_flags()->
> 	__dev_open()->
> 	dev_set_rx_mode() - >  # disables BH and grabs "dev->addr_list_lock"
> 	idpf_set_rx_mode() ->  # proceed only if VIRTCHNL2_CAP_MACFILTER is ON
> 	__dev_uc_sync() ->
> 	idpf_add_mac_filter ->
> 	idpf_add_del_mac_filters ->
> 	idpf_send_mb_msg() ->
> 	idpf_mb_clean() ->
> 	idpf_ctlq_clean_sq()   # mutex_lock(cq_lock)
> 
> Fix by converting cq_lock to a spinlock. All operations under the new
> lock are safe except freeing the DMA memory, which may use vunmap(). Fix
> by requesting a contiguous physical memory for the DMA mapping.

Hi Ahmed,

If I understand things correctly, then by safe you mean won't sleep.  But
if so my question is if the path that frees DMA memory which is updated by
this patch is run in a context where sleeping is not allowed.

> 
> Fixes: a251eee62133 ("idpf: add SRIOV support and other ndo_ops")
> Reviewed-by: Aleksandr Loktionov <aleksandr.loktionov@...el.com>
> Signed-off-by: Ahmed Zaki <ahmed.zaki@...el.com>

...