【问题标题】：lookup the lock statistic in linux kernel在 linux 内核中查找锁统计信息
【发布时间】：2017-03-10 22:21:34
【问题描述】：

最近在研究Linux的锁机制，想看看锁的持有和等待时间。

所以我通过make menuconfig打开.config文件中的CONFIG_LOCK_STAT标志，并在重新编译内核后运行命令：

# less /proc/lock_stat

我收到以下消息：

*WARNING* lock debugging disabled!! - possibly due to a lockdep warning.

只是不知道为什么，因为我已经打开了内核hack->lock会话中的所有标志。

附：我使用的环境：kernel 3.12.6 (by uname -a)。

更新：dmesg 开启 __debug_locks_off() 和 dump_stack()

[    0.000000]  [<ffffffff817516a2>] _raw_write_lock+0x72/0x80
[    0.000000]  [<ffffffff81392718>] ? irqsafe4_soft_wlock_213+0x98/0xf0
[    0.000000]  [<ffffffff81392718>] irqsafe4_soft_wlock_213+0x98/0xf0
[    0.000000]  [<ffffffff817481f5>] dotest+0x43/0x5a7
[    0.000000]  [<ffffffff81399cd6>] locking_selftest+0x1286/0x2100
[    0.000000]  [<ffffffff81f1aca9>] start_kernel+0x2d2/0x427
[    0.000000]  [<ffffffff81f1a120>] ? early_idt_handlers+0x120/0x120
[    0.000000]  [<ffffffff81f1a4c7>] x86_64_start_reservations+0x2a/0x2c
[    0.000000]  [<ffffffff81f1a5d6>] x86_64_start_kernel+0x10d/0x11c
[    0.000000]   ok  |  ok  |
[    0.000000]     hard-safe-A + unsafe-B #2/231:### __debug_locks_off called!
[    0.000000] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 3.12.6 #13
[    0.000000] Hardware name: Sony Corporation VGN-Z25TN_B/VAIO, BIOS R2140M3 08/26/2008
[    0.000000]  0000000000000002 ffffffff81c01c38 ffffffff81747f7c ffffffff81c15c98
[    0.000000]  ffffffff81c01c48 ffffffff81383d27 ffffffff81c01d60 ffffffff810d9d1e
[    0.000000]  ffffffff81c01ff8 ffffffff81c00000 ffffffff81c01fe8 ffffffff824d2d58
[    0.000000] Call Trace:
[    0.000000]  [<ffffffff81747f7c>] dump_stack+0x54/0x74
[    0.000000]  [<ffffffff81383d27>] debug_locks_off+0x17/0x50
[    0.000000]  [<ffffffff810d9d1e>] check_usage+0x10e/0x550
[    0.000000]  [<ffffffff810170f4>] ? dump_trace+0x194/0x2f0
[    0.000000]  [<ffffffff810d6a54>] ? __bfs+0x24/0x240
[    0.000000]  [<ffffffff810da1af>] check_irq_usage+0x4f/0xc0
[    0.000000]  [<ffffffff810dd1ae>] __lock_acquire+0x1bce/0x2190
[    0.000000]  [<ffffffff817511e7>] ? _raw_spin_unlock_irqrestore+0x67/0x70
[    0.000000]  [<ffffffff810c13b6>] ? vprintk_emit+0x1d6/0x630
[    0.000000]  [<ffffffff810de882>] lock_acquire+0xb2/0x160
[    0.000000]  [<ffffffff8138b936>] ? irqsafe4_hard_spin_231+0xc6/0x110
[    0.000000]  [<ffffffff8138b870>] ? irqsafe4_hard_rlock_231+0x110/0x110
[    0.000000]  [<ffffffff81750e96>] _raw_spin_lock+0x46/0x80
[    0.000000]  [<ffffffff8138b936>] ? irqsafe4_hard_spin_231+0xc6/0x110
[    0.000000]  [<ffffffff8138b936>] irqsafe4_hard_spin_231+0xc6/0x110
[    0.000000]  [<ffffffff817481f5>] dotest+0x43/0x5a7
[    0.000000]  [<ffffffff81399d22>] locking_selftest+0x12d2/0x2100
[    0.000000]  [<ffffffff81f1aca9>] start_kernel+0x2d2/0x427
[    0.000000]  [<ffffffff81f1a120>] ? early_idt_handlers+0x120/0x120
[    0.000000]  [<ffffffff81f1a4c7>] x86_64_start_reservations+0x2a/0x2c
[    0.000000]  [<ffffffff81f1a5d6>] x86_64_start_kernel+0x10d/0x11c
[    0.000000] ### __debug_locks_off called!
[    0.000000] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 3.12.6 #13
[    0.000000] Hardware name: Sony Corporation VGN-Z25TN_B/VAIO, BIOS R2140M3 08/26/2008
[    0.000000]  ffffffff81c15580 ffffffff81c01e78 ffffffff81747f7c ffffffff81cab258
[    0.000000]  ffffffff81c01e88 ffffffff81383d27 ffffffff81c01ed8 ffffffff810df539
[    0.000000]  0000000000000082 ffffffff8138b936 0000000000000092 ffffffff81cab258
[    0.000000] Call Trace:
[    0.000000]  [<ffffffff81747f7c>] dump_stack+0x54/0x74
[    0.000000]  [<ffffffff81383d27>] debug_locks_off+0x17/0x50
[    0.000000]  [<ffffffff810df539>] lock_acquired+0x2f9/0x4d0
[    0.000000]  [<ffffffff8138b936>] ? irqsafe4_hard_spin_231+0xc6/0x110
[    0.000000]  [<ffffffff8138b870>] ? irqsafe4_hard_rlock_231+0x110/0x110
[    0.000000]  [<ffffffff81750ec2>] _raw_spin_lock+0x72/0x80
[    0.000000]  [<ffffffff8138b936>] ? irqsafe4_hard_spin_231+0xc6/0x110
[    0.000000]  [<ffffffff8138b936>] irqsafe4_hard_spin_231+0xc6/0x110
[    0.000000]  [<ffffffff817481f5>] dotest+0x43/0x5a7
[    0.000000]  [<ffffffff81399d22>] locking_selftest+0x12d2/0x2100
[    0.000000]  [<ffffffff81f1aca9>] start_kernel+0x2d2/0x427
[    0.000000]  [<ffffffff81f1a120>] ? early_idt_handlers+0x120/0x120
[    0.000000]  [<ffffffff81f1a4c7>] x86_64_start_reservations+0x2a/0x2c
[    0.000000]  [<ffffffff81f1a5d6>] x86_64_start_kernel+0x10d/0x11c
[    0.000000]   ok  |### __debug_locks_off called!
[    0.000000] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 3.12.6 #13
[    0.000000] Hardware name: Sony Corporation VGN-Z25TN_B/VAIO, BIOS R2140M3 08/26/2008
[    0.000000]  0000000000000002 ffffffff81c01c38 ffffffff81747f7c ffffffff81c15c98
[    0.000000]  ffffffff81c01c48 ffffffff81383d27 ffffffff81c01d60 ffffffff810d9d1e
[    0.000000]  ffffffff81c01ff8 ffffffff81c00000 ffffffff81c01fe8 ffffffff824d3138
[    0.000000] Call Trace:
[    0.000000]  [<ffffffff81747f7c>] dump_stack+0x54/0x74
[    0.000000]  [<ffffffff81383d27>] debug_locks_off+0x17/0x50
[    0.000000]  [<ffffffff810d9d1e>] check_usage+0x10e/0x550
[    0.000000]  [<ffffffff810170f4>] ? dump_trace+0x194/0x2f0
[    0.000000]  [<ffffffff810d6a54>] ? __bfs+0x24/0x240
[    0.000000]  [<ffffffff810da1af>] check_irq_usage+0x4f/0xc0
[    0.000000]  [<ffffffff810dd1ae>] __lock_acquire+0x1bce/0x2190
[    0.000000]  [<ffffffff810d80e8>] ? lockdep_init_map+0x68/0x6d0
[    0.000000]  [<ffffffff810de882>] lock_acquire+0xb2/0x160
[    0.000000]  [<ffffffff81392636>] ? irqsafe4_hard_wlock_231+0xc6/0x110
[    0.000000]  [<ffffffff81392570>] ? irqsafe4_soft_wlock_231+0xf0/0xf0
[    0.000000]  [<ffffffff81751676>] _raw_write_lock+0x46/0x80
[    0.000000]  [<ffffffff81392636>] ? irqsafe4_hard_wlock_231+0xc6/0x110
[    0.000000]  [<ffffffff81392636>] irqsafe4_hard_wlock_231+0xc6/0x110
[    0.000000]  [<ffffffff817481f5>] dotest+0x43/0x5a7
[    0.000000]  [<ffffffff81399d35>] locking_selftest+0x12e5/0x2100
[    0.000000]  [<ffffffff81f1aca9>] start_kernel+0x2d2/0x427
[    0.000000]  [<ffffffff81f1a120>] ? early_idt_handlers+0x120/0x120
[    0.000000]  [<ffffffff81f1a4c7>] x86_64_start_reservations+0x2a/0x2c
[    0.000000]  [<ffffffff81f1a5d6>] x86_64_start_kernel+0x10d/0x11c
[    0.000000] ### __debug_locks_off called!
[    0.000000] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 3.12.6 #13
[    0.000000] Hardware name: Sony Corporation VGN-Z25TN_B/VAIO, BIOS R2140M3 08/26/2008
[    0.000000]  ffffffff81c15580 ffffffff81c01e78 ffffffff81747f7c ffffffff81cab058
[    0.000000]  ffffffff81c01e88 ffffffff81383d27 ffffffff81c01ed8 ffffffff810df539
[    0.000000]  0000000000000082 ffffffff81392636 0000000000000092 ffffffff81cab058
[    0.000000] Call Trace:
[    0.000000]  [<ffffffff81747f7c>] dump_stack+0x54/0x74
[    0.000000]  [<ffffffff81383d27>] debug_locks_off+0x17/0x50
[    0.000000]  [<ffffffff810df539>] lock_acquired+0x2f9/0x4d0
[    0.000000]  [<ffffffff81392636>] ? irqsafe4_hard_wlock_231+0xc6/0x110
[    0.000000]  [<ffffffff81392570>] ? irqsafe4_soft_wlock_231+0xf0/0xf0
[    0.000000]  [<ffffffff817516a2>] _raw_write_lock+0x72/0x80
[    0.000000]  [<ffffffff81392636>] ? irqsafe4_hard_wlock_231+0xc6/0x110
[    0.000000]  [<ffffffff81392636>] irqsafe4_hard_wlock_231+0xc6/0x110
[    0.000000]  [<ffffffff817481f5>] dotest+0x43/0x5a7
[    0.000000]  [<ffffffff81399d35>] locking_selftest+0x12e5/0x2100
[    0.000000]  [<ffffffff81f1aca9>] start_kernel+0x2d2/0x427
[    0.000000]  [<ffffffff81f1a120>] ? early_idt_handlers+0x120/0x120
[    0.000000]  [<ffffffff81f1a4c7>] x86_64_start_reservations+0x2a/0x2c
[    0.000000]  [<ffffffff81f1a5d6>] x86_64_start_kernel+0x10d/0x11c
[    0.000000]   ok  |  ok  |
[    0.000000]     soft-safe-A + unsafe-B #2/231:### __debug_locks_off called!
[    0.000000] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 3.12.6 #13
[    0.000000] Hardware name: Sony Corporation VGN-Z25TN_B/VAIO, BIOS R2140M3 08/26/2008
[    0.000000]  0000000000000006 ffffffff81c01c38 ffffffff81747f7c ffffffff81c15c98
[    0.000000]  ffffffff81c01c48 ffffffff81383d27 ffffffff81c01d60 ffffffff810d9d1e
[    0.000000]  ffffffff81c01cd8 0000000081c00000 ffffffff81c01fe8 0000000000000001
[    0.000000] Call Trace:
[    0.000000]  [<ffffffff81747f7c>] dump_stack+0x54/0x74
[    0.000000]  [<ffffffff81383d27>] debug_locks_off+0x17/0x50
[    0.000000]  [<ffffffff810d9d1e>] check_usage+0x10e/0x550
[    0.000000]  [<ffffffff810d9ac2>] ? check_usage_backwards+0x72/0x1c0
[    0.000000]  [<ffffffff810d6a54>] ? __bfs+0x24/0x240
[    0.000000]  [<ffffffff810da1af>] check_irq_usage+0x4f/0xc0
[    0.000000]  [<ffffffff810dd1cd>] __lock_acquire+0x1bed/0x2190
[    0.000000]  [<ffffffff817511e7>] ? _raw_spin_unlock_irqrestore+0x67/0x70
[    0.000000]  [<ffffffff810c13b6>] ? vprintk_emit+0x1d6/0x630
[    0.000000]  [<ffffffff810de882>] lock_acquire+0xb2/0x160
[    0.000000]  [<ffffffff8138d6f8>] ? irqsafe4_soft_spin_231+0xa8/0xf0
[    0.000000]  [<ffffffff8138d650>] ? irqsafe4_soft_rlock_231+0xf0/0xf0
[    0.000000]  [<ffffffff81750e96>] _raw_spin_lock+0x46/0x80
[    0.000000]  [<ffffffff8138d6f8>] ? irqsafe4_soft_spin_231+0xa8/0xf0
[    0.000000]  [<ffffffff8138d6f8>] irqsafe4_soft_spin_231+0xa8/0xf0
[    0.000000]  [<ffffffff817481f5>] dotest+0x43/0x5a7
[    0.000000]  [<ffffffff81399d81>] locking_selftest+0x1331/0x2100
[    0.000000]  [<ffffffff81f1aca9>] start_kernel+0x2d2/0x427
[    0.000000]  [<ffffffff81f1a120>] ? early_idt_handlers+0x120/0x120
[    0.000000]  [<ffffffff81f1a4c7>] x86_64_start_reservations+0x2a/0x2c
[    0.000000]  [<ffffffff81f1a5d6>] x86_64_start_kernel+0x10d/0x11c
[    0.000000] ### __debug_locks_off called!
[    0.000000] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 3.12.6 #13
[    0.000000] Hardware name: Sony Corporation VGN-Z25TN_B/VAIO, BIOS R2140M3 08/26/2008
[    0.000000]  ffffffff81c15580 ffffffff81c01e78 ffffffff81747f7c ffffffff81cab258
[    0.000000]  ffffffff81c01e88 ffffffff81383d27 ffffffff81c01ed8 ffffffff810df539
[    0.000000]  0000000000000282 ffffffff8138d6f8 0000000000000292 ffffffff81cab258
[    0.000000] Call Trace:
[    0.000000]  [<ffffffff81747f7c>] dump_stack+0x54/0x74
[    0.000000]  [<ffffffff81383d27>] debug_locks_off+0x17/0x50
[    0.000000]  [<ffffffff810df539>] lock_acquired+0x2f9/0x4d0
[    0.000000]  [<ffffffff8138d6f8>] ? irqsafe4_soft_spin_231+0xa8/0xf0
[    0.000000]  [<ffffffff8138d650>] ? irqsafe4_soft_rlock_231+0xf0/0xf0
[    0.000000]  [<ffffffff81750ec2>] _raw_spin_lock+0x72/0x80
[    0.000000]  [<ffffffff8138d6f8>] ? irqsafe4_soft_spin_231+0xa8/0xf0
[    0.000000]  [<ffffffff8138d6f8>] irqsafe4_soft_spin_231+0xa8/0xf0
[    0.000000]  [<ffffffff817481f5>] dotest+0x43/0x5a7
[    0.000000]  [<ffffffff81399d81>] locking_selftest+0x1331/0x2100
[    0.000000]  [<ffffffff81f1aca9>] start_kernel+0x2d2/0x427
[    0.000000]  [<ffffffff81f1a120>] ? early_idt_handlers+0x120/0x120
[    0.000000]  [<ffffffff81f1a4c7>] x86_64_start_reservations+0x2a/0x2c
[    0.000000]  [<ffffffff81f1a5d6>] x86_64_start_kernel+0x10d/0x11c
[    0.000000]   ok  |### __debug_locks_off called!
[    0.000000] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 3.12.6 #13
[    0.000000] Hardware name: Sony Corporation VGN-Z25TN_B/VAIO, BIOS R2140M3 08/26/2008
[    0.000000]  0000000000000006 ffffffff81c01c38 ffffffff81747f7c ffffffff81c15c98
[    0.000000]  ffffffff81c01c48 ffffffff81383d27 ffffffff81c01d60 ffffffff810d9d1e
[    0.000000]  ffffffff81c01cd8 0000000081c00000 ffffffff81c01fe8 0000000000000001
[    0.000000] Call Trace:
[    0.000000]  [<ffffffff81747f7c>] dump_stack+0x54/0x74
[    0.000000]  [<ffffffff81383d27>] debug_locks_off+0x17/0x50
[    0.000000]  [<ffffffff810d9d1e>] check_usage+0x10e/0x550
[    0.000000]  [<ffffffff810d9ac2>] ? check_usage_backwards+0x72/0x1c0
[    0.000000]  [<ffffffff810d6a54>] ? __bfs+0x24/0x240
[    0.000000]  [<ffffffff810da1af>] check_irq_usage+0x4f/0xc0
[    0.000000]  [<ffffffff810dd1cd>] __lock_acquire+0x1bed/0x2190
[    0.000000]  [<ffffffff810d80e8>] ? lockdep_init_map+0x68/0x6d0
[    0.000000]  [<ffffffff810de882>] lock_acquire+0xb2/0x160
[    0.000000]  [<ffffffff81392528>] ? irqsafe4_soft_wlock_231+0xa8/0xf0
[    0.000000]  [<ffffffff81392480>] ? irqsafe4_hard_wlock_312+0x110/0x110
[    0.000000]  [<ffffffff81751676>] _raw_write_lock+0x46/0x80
[    0.000000]  [<ffffffff81392528>] ? irqsafe4_soft_wlock_231+0xa8/0xf0
[    0.000000]  [<ffffffff81392528>] irqsafe4_soft_wlock_231+0xa8/0xf0
[    0.000000]  [<ffffffff817481f5>] dotest+0x43/0x5a7
[    0.000000]  [<ffffffff81399d94>] locking_selftest+0x1344/0x2100
[    0.000000]  [<ffffffff81f1aca9>] start_kernel+0x2d2/0x427
[    0.000000]  [<ffffffff81f1a120>] ? early_idt_handlers+0x120/0x120
[    0.000000]  [<ffffffff81f1a4c7>] x86_64_start_reservations+0x2a/0x2c
[    0.000000]  [<ffffffff81f1a5d6>] x86_64_start_kernel+0x10d/0x11c
[    0.000000] ### __debug_locks_off called!
[    0.000000] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 3.12.6 #13
[    0.000000] Hardware name: Sony Corporation VGN-Z25TN_B/VAIO, BIOS R2140M3 08/26/2008
[    0.000000]  ffffffff81c15580 ffffffff81c01e78 ffffffff81747f7c ffffffff81cab058
[    0.000000]  ffffffff81c01e88 ffffffff81383d27 ffffffff81c01ed8 ffffffff810df539
[    0.000000]  0000000000000282 ffffffff81392528 0000000000000292 ffffffff81cab058
[    0.000000] Call Trace:
[    0.000000]  [<ffffffff81747f7c>] dump_stack+0x54/0x74
[    0.000000]  [<ffffffff81383d27>] debug_locks_off+0x17/0x50
[    0.000000]  [<ffffffff810df539>] lock_acquired+0x2f9/0x4d0
[    0.000000]  [<ffffffff81392528>] ? irqsafe4_soft_wlock_231+0xa8/0xf0
[    0.000000]  [<ffffffff81392480>] ? irqsafe4_hard_wlock_312+0x110/0x110
[    0.000000]  [<ffffffff817516a2>] _raw_write_lock+0x72/0x80
[    0.000000]  [<ffffffff81392528>] ? irqsafe4_soft_wlock_231+0xa8/0xf0
[    0.000000]  [<ffffffff81392528>] irqsafe4_soft_wlock_231+0xa8/0xf0
[    0.000000]  [<ffffffff817481f5>] dotest+0x43/0x5a7
[    0.000000]  [<ffffffff81399d94>] locking_selftest+0x1344/0x2100
[    0.000000]  [<ffffffff81f1aca9>] start_kernel+0x2d2/0x427
[    0.000000]  [<ffffffff81f1a120>] ? early_idt_handlers+0x120/0x120
[    0.000000]  [<ffffffff81f1a4c7>] x86_64_start_reservations+0x2a/0x2c
[    0.000000]  [<ffffffff81f1a5d6>] x86_64_start_kernel+0x10d/0x11c
[    0.000000]   ok  |  ok  |
[    0.000000]     hard-safe-A + unsafe-B #2/312:### __debug_locks_off called!
[    0.000000] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 3.12.6 #13
[    0.000000] Hardware name: Sony Corporation VGN-Z25TN_B/VAIO, BIOS R2140M3 08/26/2008
[    0.000000]  0000000000000000 ffffffff81c01cb0 ffffffff81747f7c ffffffff81c15c98
[    0.000000]  ffffffff81c01cc0 ffffffff81383d27 ffffffff81c01d50 ffffffff810d9adf
[    0.000000]  0000000000000000 ffffffff8288dec0 ffffffff824d43a8 0000000081c01d60
[    0.000000] Call Trace:
[    0.000000]  [<ffffffff81747f7c>] dump_stack+0x54/0x74
[    0.000000]  [<ffffffff81383d27>] debug_locks_off+0x17/0x50
[    0.000000]  [<ffffffff810d9adf>] check_usage_backwards+0x8f/0x1c0
[    0.000000]  [<ffffffff810da9c2>] mark_lock+0x412/0x820
[    0.000000]  [<ffffffff810d9a50>] ? check_usage_forwards+0x1c0/0x1c0
[    0.000000]  [<ffffffff810dbf68>] __lock_acquire+0x988/0x2190
[    0.000000]  [<ffffffff817511e7>] ? _raw_spin_unlock_irqrestore+0x67/0x70
[    0.000000]  [<ffffffff810c13b6>] ? vprintk_emit+0x1d6/0x630
[    0.000000]  [<ffffffff810de882>] lock_acquire+0xb2/0x160
[    0.000000]  [<ffffffff8138b72e>] ? irqsafe4_hard_spin_312+0xde/0x110
[    0.000000]  [<ffffffff8138b650>] ? irqsafe4_hard_rlock_312+0x110/0x110
[    0.000000]  [<ffffffff81750e96>] _raw_spin_lock+0x46/0x80
[    0.000000]  [<ffffffff8138b72e>] ? irqsafe4_hard_spin_312+0xde/0x110
[    0.000000]  [<ffffffff8138b72e>] irqsafe4_hard_spin_312+0xde/0x110
[    0.000000]  [<ffffffff817481f5>] dotest+0x43/0x5a7
[    0.000000]  [<ffffffff81399de0>] locking_selftest+0x1390/0x2100
[    0.000000]  [<ffffffff81f1aca9>] start_kernel+0x2d2/0x427
[    0.000000]  [<ffffffff81f1a120>] ? early_idt_handlers+0x120/0x120
[    0.000000]  [<ffffffff81f1a4c7>] x86_64_start_reservations+0x2a/0x2c
[    0.000000]  [<ffffffff81f1a5d6>] x86_64_start_kernel+0x10d/0x11c
[    0.000000] ### __debug_locks_off called!
[    0.000000] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 3.12.6 #13
[    0.000000] Hardware name: Sony Corporation VGN-Z25TN_B/VAIO, BIOS R2140M3 08/26/2008
[    0.000000]  ffffffff81c15580 ffffffff81c01e78 ffffffff81747f7c ffffffff81cab258
[    0.000000]  ffffffff81c01e88 ffffffff81383d27 ffffffff81c01ed8 ffffffff810df595
[    0.000000]  0000000000000282 ffffffff8138b72e 0000000000000292 ffffffff81cab258
[    0.000000] Call Trace:
[    0.000000]  [<ffffffff81747f7c>] dump_stack+0x54/0x74
[    0.000000]  [<ffffffff81383d27>] debug_locks_off+0x17/0x50
[    0.000000]  [<ffffffff810df595>] lock_acquired+0x355/0x4d0
[    0.000000]  [<ffffffff8138b72e>] ? irqsafe4_hard_spin_312+0xde/0x110
[    0.000000]  [<ffffffff8138b650>] ? irqsafe4_hard_rlock_312+0x110/0x110
[    0.000000]  [<ffffffff81750ec2>] _raw_spin_lock+0x72/0x80
[    0.000000]  [<ffffffff8138b72e>] ? irqsafe4_hard_spin_312+0xde/0x110
[    0.000000]  [<ffffffff8138b72e>] irqsafe4_hard_spin_312+0xde/0x110
[    0.000000]  [<ffffffff817481f5>] dotest+0x43/0x5a7
[    0.000000]  [<ffffffff81399de0>] locking_selftest+0x1390/0x2100
[    0.000000]  [<ffffffff81f1aca9>] start_kernel+0x2d2/0x427
[    0.000000]  [<ffffffff81f1a120>] ? early_idt_handlers+0x120/0x120
[    0.000000]  [<ffffffff81f1a4c7>] 
[    0.000000]  [<ffffffff81f1a5d6>] x86_64_start_kernel+0x10d/0x11c
[    0.000000]   ok  |
[    0.000000] -------------------------------------------------------
[    0.000000] Good, all 253 testcases passed! |
[    0.000000] ---------------------------------
[    0.000000] hpet clockevent registered

【问题讨论】：

lockdep warning 是关于运行时 lockdep 检查的警告。 grep dmesg 输出 lockdep 字符串。

标签： linux linux-kernel

【解决方案1】：

启用锁统计

首先确保启用锁统计收集。来自Documentation/locking/lockstat.txt：

配置

通过CONFIG_LOCK_STAT启用锁定统计信息。

用法

启用统计信息收集：
# echo 1 >/proc/sys/kernel/lock_stat
禁用统计数据收集：
# echo 0 >/proc/sys/kernel/lock_stat
查看当前锁统计：

( 行号不是实际输出的一部分，为了解释清楚而完成下面）
# less /proc/lock_stat

因此，请务必先启用锁统计信息收集。

检查内核日志中的 lockdep 警告

现在，让我们看一下打印警告消息的代码：

kernel/locking/lockdep_proc.c : seq_header():

if (unlikely(!debug_locks))
    seq_printf(m, "*WARNING* lock debugging disabled!! - possibly due to a lockdep warning\n");

debug_locks_off() 函数将这个 debug_locks 变量设置为 0（禁用），而该函数又可以从很多的地方调用。我们看一下定义这个变量的地方：

lib/debug_locks.c:

/*
 * We want to turn all lock-debugging facilities on/off at once,
 * via a global flag. The reason is that once a single bug has been
 * detected and reported, there might be cascade of followup bugs
 * that would just muddy the log. So we report the first one and
 * shut up after that.
 */
int debug_locks = 1;
EXPORT_SYMBOL_GPL(debug_locks);

对该变量的评论说明您看到该警告的原因。

因此，请检查您的内核日志（通过dmesg 命令）以查看lockdep 机制实际发现的错误。您可能会找到一个，它会解释为什么禁用锁定调试。

更新

关于此消息：

[0.084000] SMP 替代方案：lockdep：修复替代方案

这似乎与您的实际问题无关。此消息正在由下一个代码打印：

arch/x86/kernel/alternative.c : alternatives_enable_smp():

#ifdef CONFIG_LOCKDEP
   /*
    * Older binutils section handling bug prevented
    * alternatives-replacement from working reliably.
    *
    * If this still occurs then you should see a hang
    * or crash shortly after this line:
    */
   pr_info("lockdep: fixing up alternatives\n");
#endif

此代码已过时且已过时，并且已通过此提交删除到较新的内核版本中：

lockdep, x86/alternatives: Drop ancient lockdep fixup message

所以我认为这是导致禁用收集锁统计信息的其他原因。很难说到底是什么。我唯一能想到的就是修改内核，以便您可以查看导致锁定调试禁用的原因，重建内核并查看内核日志以找出调用锁定调试禁用的位置。

所以，如果你能做到这一点，修改__debug_locks_off()函数如下：

static inline int __debug_locks_off(void)
{
    /* ---- Add this code ---- */
    pr_err("### __debug_locks_off() called!\n");
    dump_stack();
    /* ----------------------- */

    return xchg(&debug_locks, 0);
}

另外，在该文件的顶部添加 #include <linux/printk.h> 行，以防万一。

然后重建你的内核，运行它并提供整个dmesg 输出。应该足以告诉它在哪里被禁用了。

更新 2

正如我从您提供的回溯中看到的，所有dump_stack() 调用（您添加到__debug_locks_off() 函数）- 它们从locking_selftest() 函数调用，而这又只是一些单元测试例程。我们来看看：locking_selftest()。这里需要注意的是这段代码：

} else {
    printk("-------------------------------------------------------\n");
    printk("Good, all %3d testcases passed! |\n",
        testcase_successes);
    printk("---------------------------------\n");
    debug_locks = 1;
}

因此，您可以看到，在您的情况下，locking_selftest() 的末尾已启用（“on”）变量 debug_locks。考虑到您提供的所有消息实际上都是从 locking_selftest() 触发的，我可以说这些消息不会导致您的问题（已禁用 debug_locks 变量）。

所以你仍然需要弄清楚这个debug_locks 变量在哪里以及为什么（在你的情况下）被禁用。让我们从这个开始：请与我们分享完整的dmesg 输出（您可以使用一些 pastebin 服务，只需将链接添加到您的问题或作为新评论）。您可能忽略了 dmesg 输出中实际上相关的一些 __debug_locks_off() 调用（不是从该自测试例程调用的）。

【讨论】：

谢谢你们的帮助，
Dmesg 和 veep 步调一致，得到消息：SMP 替代方案：lockdep：修复替代方案。我看不出有什么奇怪的地方？
请提供完整的dmesg输出。
提供了dmesg输出~~谢谢！
我在答案中添加了 UPDATE 部分。希望它能解决您的问题。

【解决方案2】：

你可以设置CONFIG_PROVE_RCU_REPEATEDLY=y，这意味着“不要在第一次splat时禁用PROVE_RCU”

【讨论】：