[patch 0/1] staging: speakup: fix speakup-r empty line lockup

[Okash Khawaja]

Hi,

This patch fixes kernel lockup shown by lockdep log below. Further
details are in patch header.

Samuel, please note that I removed initialisation of the static int
in_keyboard_notifier to zero as that is not required and reported as
error by checkpatch.

Thanks,
Okash


[ 1293.803242] ============================================
[ 1293.803304] WARNING: possible recursive locking detected
[ 1293.803369] 4.12.2-ARCH+ #7 Tainted: G         C O
[ 1293.803442] --------------------------------------------
[ 1293.803504] swapper/0/0 is trying to acquire lock:
[ 1293.803562]  (&(&dev->event_lock)->rlock){-.-...}, at: [<ffffffff8153b0ae>] input_event+0x3e/0x80
[ 1293.803671]
[ 1293.803671] but task is already holding lock:
[ 1293.803740]  (&(&dev->event_lock)->rlock){-.-...}, at: [<ffffffff8153b0ae>] input_event+0x3e/0x80
[ 1293.803843]
[ 1293.803843] other info that might help us debug this:
[ 1293.803916]  Possible unsafe locking scenario:
[ 1293.803916]
[ 1293.803984]        CPU0
[ 1293.804021]        ----
[ 1293.804054]   lock(&(&dev->event_lock)->rlock);
[ 1293.804109]   lock(&(&dev->event_lock)->rlock);
[ 1293.804164]
[ 1293.804164]  *** DEADLOCK ***
[ 1293.804164]
[ 1293.804233]  May be due to missing lock nesting notation
[ 1293.804233]
[ 1293.804311] 6 locks held by swapper/0/0:
[ 1293.804359]  #0:  (&serio->lock){-.-...}, at: [<ffffffffa0007fea>] serio_interrupt+0x2a/0x90 [serio]
[ 1293.804469]  #1:  (&(&dev->event_lock)->rlock){-.-...}, at: [<ffffffff8153b0ae>] input_event+0x3e/0x80
[ 1293.804577]  #2:  (rcu_read_lock){......}, at: [<ffffffff8153a6b5>] input_pass_values.part.1+0x5/0x260
[ 1293.804685]  #3:  (kbd_event_lock){-.-...}, at: [<ffffffff814a091c>] kbd_event+0x3c/0x710
[ 1293.804781]  #4:  (rcu_read_lock){......}, at: [<ffffffff810b1135>] __atomic_notifier_call_chain+0x5/0x110
[ 1293.804898]  #5:  (speakup_info.spinlock){-.-...}, at: [<ffffffffa06690ac>] keyboard_notifier_call+0xfc/0xcc0 [speakup]
[ 1293.805028]
[ 1293.805028] stack backtrace:
[ 1293.805084] CPU: 0 PID: 0 Comm: swapper/0 Tainted: G         C O    4.12.2-ARCH+ #7
[ 1293.805168] Hardware name: Dell Inc. Inspiron 7559/0H0CC0, BIOS 1.2.2 01/22/2017
[ 1293.805250] Call Trace:
[ 1293.805284]  <IRQ>
[ 1293.805320]  dump_stack+0x8e/0xcd
[ 1293.805366]  __lock_acquire+0x87d/0x1a20
[ 1293.805423]  ? native_apic_wait_icr_idle+0x1f/0x30
[ 1293.805482]  ? arch_irq_work_raise+0x34/0x40
[ 1293.805537]  lock_acquire+0xa5/0x250
[ 1293.805583]  ? lock_acquire+0xa5/0x250
[ 1293.805632]  ? input_event+0x3e/0x80
[ 1293.805683]  _raw_spin_lock_irqsave+0x4d/0x90
[ 1293.805736]  ? input_event+0x3e/0x80
[ 1293.805782]  input_event+0x3e/0x80
[ 1293.805833]  speakup_fake_down_arrow2+0x57/0xd0 [speakup]
[ 1293.805902]  read_all_doc+0xd7/0xe0 [speakup]
[ 1293.805960]  ? kbd_fakekey+0x40/0x40 [speakup]
[ 1293.806020]  keyboard_notifier_call+0xbe8/0xcc0 [speakup]
[ 1293.806085]  ? lock_acquire+0xa5/0x250
[ 1293.806136]  notifier_call_chain+0x4a/0x70
[ 1293.806191]  __atomic_notifier_call_chain+0x72/0x110
[ 1293.806254]  atomic_notifier_call_chain+0x16/0x20
[ 1293.806311]  kbd_event+0x320/0x710
[ 1293.806361]  input_to_handler+0xdb/0xf0
[ 1293.806411]  input_pass_values.part.1+0x1b3/0x260
[ 1293.806469]  input_handle_event+0xe4/0x150
[ 1293.806608]  input_event+0x52/0x80
[ 1293.806660]  atkbd_interrupt+0x50a/0x7c0 [atkbd]
[ 1293.806719]  serio_interrupt+0x46/0x90 [serio]
[ 1293.806778]  i8042_interrupt+0x20d/0x3b0 [i8042]
[ 1293.806839]  __handle_irq_event_percpu+0x45/0x390
[ 1293.806899]  handle_irq_event_percpu+0x32/0x80
[ 1293.806955]  handle_irq_event+0x39/0x60
[ 1293.807007]  handle_edge_irq+0x78/0x130
[ 1293.808787]  handle_irq+0x1a/0x30
[ 1293.809755]  do_IRQ+0x58/0x110
[ 1293.810712]  common_interrupt+0x93/0x93
[ 1293.811644] RIP: 0010:cpuidle_enter_state+0x143/0x390
[ 1293.812575] RSP: 0018:ffffffff81c03dc0 EFLAGS: 00000202 ORIG_RAX: ffffffffffffffce
[ 1293.813518] RAX: ffffffff81c18500 RBX: 0000012d3ca4a19b RCX: 0000000000000000
[ 1293.814462] RDX: ffffffff81c18500 RSI: 0000000000000001 RDI: ffffffff81c18500
[ 1293.815398] RBP: ffffffff81c03e00 R08: cccccccccccccccd R09: 0000000000000000
[ 1293.816335] R10: 0000000000000000 R11: 0000000000000000 R12: ffff8804707e3100
[ 1293.817261] R13: 0000000000000000 R14: 0000000000000008 R15: ffffffff81cc7898
[ 1293.818179]  </IRQ>
[ 1293.819081]  cpuidle_enter+0x17/0x20
[ 1293.819986]  call_cpuidle+0x23/0x40
[ 1293.820884]  do_idle+0x18f/0x1f0
[ 1293.821776]  cpu_startup_entry+0x71/0x80
[ 1293.822662]  rest_init+0x131/0x140
[ 1293.823547]  start_kernel+0x44d/0x46e
[ 1293.824426]  ? early_idt_handler_array+0x120/0x120
[ 1293.825326]  x86_64_start_reservations+0x2f/0x31
[ 1293.826186]  x86_64_start_kernel+0x141/0x164
[ 1293.827045]  secondary_startup_64+0x9f/0x9f