In the function ieee80211_tx_dequeue() there is a particular locking
sequence:
begin:
spin_lock(&local->queue_stop_reason_lock);
q_stopped = local->queue_stop_reasons[q];
spin_unlock(&local->queue_stop_reason_lock);
However small the chance (increased by ftracetest), an asynchronous
interrupt can occur in between of spin_lock() and spin_unlock(),
and the interrupt routine will attempt to lock the same
&local->queue_stop_reason_lock again.
This will cause a costly reset of the CPU and the wifi device or an
altogether hang in the single CPU and single core scenario.
The only remaining spin_lock(&local->queue_stop_reason_lock) that
did not disable interrupts was patched, which should prevent any
deadlocks on the same CPU/core and the same wifi device.
This is the probable trace of the deadlock:
kernel: ================================
kernel: WARNING: inconsistent lock state
kernel: 6.3.0-rc6-mt-20230401-00001-gf86822a1170f #4 Tainted: G W
kernel: --------------------------------
kernel: inconsistent {IN-SOFTIRQ-W} -> {SOFTIRQ-ON-W} usage.
kernel: kworker/5:0/25656 [HC0[0]:SC0[0]:HE1:SE1] takes:
kernel: ffff9d6190779478 (&local->queue_stop_reason_lock){+.?.}-{2:2}, at: return_to_handler+0x0/0x40
kernel: {IN-SOFTIRQ-W} state was registered at:
kernel: lock_acquire+0xc7/0x2d0
kernel: _raw_spin_lock+0x36/0x50
kernel: ieee80211_tx_dequeue+0xb4/0x1330 [mac80211]
kernel: iwl_mvm_mac_itxq_xmit+0xae/0x210 [iwlmvm]
kernel: iwl_mvm_mac_wake_tx_queue+0x2d/0xd0 [iwlmvm]
kernel: ieee80211_queue_skb+0x450/0x730 [mac80211]
kernel: __ieee80211_xmit_fast.constprop.66+0x834/0xa50 [mac80211]
kernel: __ieee80211_subif_start_xmit+0x217/0x530 [mac80211]
kernel: ieee80211_subif_start_xmit+0x60/0x580 [mac80211]
kernel: dev_hard_start_xmit+0xb5/0x260
kernel: __dev_queue_xmit+0xdbe/0x1200
kernel: neigh_resolve_output+0x166/0x260
kernel: ip_finish_output2+0x216/0xb80
kernel: __ip_finish_output+0x2a4/0x4d0
kernel: ip_finish_output+0x2d/0xd0
kernel: ip_output+0x82/0x2b0
kernel: ip_local_out+0xec/0x110
kernel: igmpv3_sendpack+0x5c/0x90
kernel: igmp_ifc_timer_expire+0x26e/0x4e0
kernel: call_timer_fn+0xa5/0x230
kernel: run_timer_softirq+0x27f/0x550
kernel: __do_softirq+0xb4/0x3a4
kernel: irq_exit_rcu+0x9b/0xc0
kernel: sysvec_apic_timer_interrupt+0x80/0xa0
kernel: asm_sysvec_apic_timer_interrupt+0x1f/0x30
kernel: _raw_spin_unlock_irqrestore+0x3f/0x70
kernel: free_to_partial_list+0x3d6/0x590
kernel: __slab_free+0x1b7/0x310
kernel: kmem_cache_free+0x52d/0x550
kernel: putname+0x5d/0x70
kernel: do_sys_openat2+0x1d7/0x310
kernel: do_sys_open+0x51/0x80
kernel: __x64_sys_openat+0x24/0x30
kernel: do_syscall_64+0x5c/0x90
kernel: entry_SYSCALL_64_after_hwframe+0x72/0xdc
kernel: irq event stamp: 5120729
kernel: hardirqs last enabled at (5120729): [<ffffffff9d149936>] trace_graph_return+0xd6/0x120
kernel: hardirqs last disabled at (5120728): [<ffffffff9d149950>] trace_graph_return+0xf0/0x120
kernel: softirqs last enabled at (5069900): [<ffffffff9cf65b60>] return_to_handler+0x0/0x40
kernel: softirqs last disabled at (5067555): [<ffffffff9cf65b60>] return_to_handler+0x0/0x40
kernel:
other info that might help us debug this:
kernel: Possible unsafe locking scenario:
kernel: CPU0
kernel: ----
kernel: lock(&local->queue_stop_reason_lock);
kernel: <Interrupt>
kernel: lock(&local->queue_stop_reason_lock);
kernel:
*** DEADLOCK ***
kernel: 8 locks held by kworker/5:0/25656:
kernel: #0: ffff9d618009d138 ((wq_completion)events_freezable){+.+.}-{0:0}, at: process_one_work+0x1ca/0x530
kernel: #1: ffffb1ef4637fe68 ((work_completion)(&local->restart_work)){+.+.}-{0:0}, at: process_one_work+0x1ce/0x530
kernel: #2: ffffffff9f166548 (rtnl_mutex){+.+.}-{3:3}, at: return_to_handler+0x0/0x40
kernel: #3: ffff9d6190778728 (&rdev->wiphy.mtx){+.+.}-{3:3}, at: return_to_handler+0x0/0x40
kernel: #4: ffff9d619077b480 (&mvm->mutex){+.+.}-{3:3}, at: return_to_handler+0x0/0x40
kernel: #5: ffff9d61907bacd8 (&trans_pcie->mutex){+.+.}-{3:3}, at: return_to_handler+0x0/0x40
kernel: #6: ffffffff9ef9cda0 (rcu_read_lock){....}-{1:2}, at: iwl_mvm_queue_state_change+0x59/0x3a0 [iwlmvm]
kernel: #7: ffffffff9ef9cda0 (rcu_read_lock){....}-{1:2}, at: iwl_mvm_mac_itxq_xmit+0x42/0x210 [iwlmvm]
kernel:
stack backtrace:
kernel: CPU: 5 PID: 25656 Comm: kworker/5:0 Tainted: G W 6.3.0-rc6-mt-20230401-00001-gf86822a1170f #4
kernel: Hardware name: LENOVO 82H8/LNVNB161216, BIOS GGCN51WW 11/16/2022
kernel: Workqueue: events_freezable ieee80211_restart_work [mac80211]
kernel: Call Trace:
kernel: <TASK>
kernel: ? ftrace_regs_caller_end+0x66/0x66
kernel: dump_stack_lvl+0x5f/0xa0
kernel: dump_stack+0x14/0x20
kernel: print_usage_bug.part.46+0x208/0x2a0
kernel: mark_lock.part.47+0x605/0x630
kernel: ? sched_clock+0xd/0x20
kernel: ? trace_clock_local+0x14/0x30
kernel: ? __rb_reserve_next+0x5f/0x490
kernel: ? _raw_spin_lock+0x1b/0x50
kernel: __lock_acquire+0x464/0x1990
kernel: ? mark_held_locks+0x4e/0x80
kernel: lock_acquire+0xc7/0x2d0
kernel: ? ftrace_regs_caller_end+0x66/0x66
kernel: ? ftrace_return_to_handler+0x8b/0x100
kernel: ? preempt_count_add+0x4/0x70
kernel: _raw_spin_lock+0x36/0x50
kernel: ? ftrace_regs_caller_end+0x66/0x66
kernel: ? ftrace_regs_caller_end+0x66/0x66
kernel: ieee80211_tx_dequeue+0xb4/0x1330 [mac80211]
kernel: ? prepare_ftrace_return+0xc5/0x190
kernel: ? ftrace_graph_func+0x16/0x20
kernel: ? 0xffffffffc02ab0b1
kernel: ? lock_acquire+0xc7/0x2d0
kernel: ? iwl_mvm_mac_itxq_xmit+0x42/0x210 [iwlmvm]
kernel: ? ieee80211_tx_dequeue+0x9/0x1330 [mac80211]
kernel: ? __rcu_read_lock+0x4/0x40
kernel: ? ftrace_regs_caller_end+0x66/0x66
kernel: iwl_mvm_mac_itxq_xmit+0xae/0x210 [iwlmvm]
kernel: ? ftrace_regs_caller_end+0x66/0x66
kernel: iwl_mvm_queue_state_change+0x311/0x3a0 [iwlmvm]
kernel: ? ftrace_regs_caller_end+0x66/0x66
kernel: iwl_mvm_wake_sw_queue+0x17/0x20 [iwlmvm]
kernel: ? ftrace_regs_caller_end+0x66/0x66
kernel: iwl_txq_gen2_unmap+0x1c9/0x1f0 [iwlwifi]
kernel: ? ftrace_regs_caller_end+0x66/0x66
kernel: iwl_txq_gen2_free+0x55/0x130 [iwlwifi]
kernel: ? ftrace_regs_caller_end+0x66/0x66
kernel: iwl_txq_gen2_tx_free+0x63/0x80 [iwlwifi]
kernel: ? ftrace_regs_caller_end+0x66/0x66
kernel: _iwl_trans_pcie_gen2_stop_device+0x3f3/0x5b0 [iwlwifi]
kernel: ? _iwl_trans_pcie_gen2_stop_device+0x9/0x5b0 [iwlwifi]
kernel: ? mutex_lock_nested+0x4/0x30
kernel: ? ftrace_regs_caller_end+0x66/0x66
kernel: iwl_trans_pcie_gen2_stop_device+0x5f/0x90 [iwlwifi]
kernel: ? ftrace_regs_caller_end+0x66/0x66
kernel: iwl_mvm_stop_device+0x78/0xd0 [iwlmvm]
kernel: ? ftrace_regs_caller_end+0x66/0x66
kernel: __iwl_mvm_mac_start+0x114/0x210 [iwlmvm]
kernel: ? ftrace_regs_caller_end+0x66/0x66
kernel: iwl_mvm_mac_start+0x76/0x150 [iwlmvm]
kernel: ? ftrace_regs_caller_end+0x66/0x66
kernel: drv_start+0x79/0x180 [mac80211]
kernel: ? ftrace_regs_caller_end+0x66/0x66
kernel: ieee80211_reconfig+0x1523/0x1ce0 [mac80211]
kernel: ? synchronize_net+0x4/0x50
kernel: ? ftrace_regs_caller_end+0x66/0x66
kernel: ieee80211_restart_work+0x108/0x170 [mac80211]
kernel: ? ftrace_regs_caller_end+0x66/0x66
kernel: process_one_work+0x250/0x530
kernel: ? ftrace_regs_caller_end+0x66/0x66
kernel: worker_thread+0x48/0x3a0
kernel: ? __pfx_worker_thread+0x10/0x10
kernel: kthread+0x10f/0x140
kernel: ? __pfx_kthread+0x10/0x10
kernel: ret_from_fork+0x29/0x50
kernel: </TASK>
Fixes: 4444bc2116ae ("wifi: mac80211: Proper mark iTXQs for resumption")
Link: https://lore.kernel.org/all/1f58a0d1-d2b9-d851-73c3-93fcc607501c@xxxxxxxxxxxx/
Reported-by: Mirsad Goran Todorovac <mirsad.todorovac@xxxxxxxxxxxx>
Cc: Gregory Greenman <gregory.greenman@xxxxxxxxx>
Cc: Johannes Berg <johannes.berg@xxxxxxxxx>
Link: https://lore.kernel.org/all/cdc80531-f25f-6f9d-b15f-25e16130b53a@xxxxxxxxxxxx/
Cc: David S. Miller <davem@xxxxxxxxxxxxx>
Cc: Eric Dumazet <edumazet@xxxxxxxxxx>
Cc: Jakub Kicinski <kuba@xxxxxxxxxx>
Cc: Paolo Abeni <pabeni@xxxxxxxxxx>
Cc: Leon Romanovsky <leon@xxxxxxxxxx>
Cc: Alexander Wetzel <alexander@xxxxxxxxxxxxxx>
Signed-off-by: Mirsad Goran Todorovac <mirsad.todorovac@xxxxxxxxxxxx>
---
v3 -> v4:
- Added whole lockdep trace as advised.
- Trimmed irrelevant line prefix.
v2 -> v3:
- Fix the Fixes: tag as advised.
- Change the net: to wifi: to comply with the original patch that
is being fixed.
v1 -> v2:
- Minor rewording and clarification.
- Cc:-ed people that replied to the original bug report (forgotten
in v1 by omission).
net/mac80211/tx.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/net/mac80211/tx.c b/net/mac80211/tx.c
index 7699fb410670..45cb8e7bcc61 100644
--- a/net/mac80211/tx.c
+++ b/net/mac80211/tx.c
@@ -3781,6 +3781,7 @@ struct sk_buff *ieee80211_tx_dequeue(struct ieee80211_hw *hw,
ieee80211_tx_result r;
struct ieee80211_vif *vif = txq->vif;
int q = vif->hw_queue[txq->ac];
+ unsigned long flags;
bool q_stopped;
WARN_ON_ONCE(softirq_count() == 0);
@@ -3789,9 +3790,9 @@ struct sk_buff *ieee80211_tx_dequeue(struct ieee80211_hw *hw,
return NULL;
begin:
- spin_lock(&local->queue_stop_reason_lock);
+ spin_lock_irqsave(&local->queue_stop_reason_lock, flags);
q_stopped = local->queue_stop_reasons[q];
- spin_unlock(&local->queue_stop_reason_lock);
+ spin_unlock_irqrestore(&local->queue_stop_reason_lock, flags);
if (unlikely(q_stopped)) {
/* mark for waking later */
--
2.30.2
