(資料圖)

2、常見的死鎖方式

常見死鎖的2種方式：

常見的死鎖有以下4種情況：

內核提供了Lockdep來檢測死鎖的異常情況。

3、Lockdep 內核配置

4、Lockdep 初探

鎖的幾個狀態：

5、Lockdep 檢查規則

單鎖狀態規則如下：（1）一個軟中斷不安全的鎖類也是硬中斷不安全的鎖類。

（2）任何一個鎖類，不可能同時是硬中斷安全的和硬中斷不安全的，也不可能同時是軟中斷安全的和軟中斷不安全的。也就是說：硬中斷安全和硬中斷不安全是互斥的，軟中斷安全和軟中斷不安全也是互斥的。

多鎖依賴規則如下：（1）同一個鎖類不能被獲取兩次，否則可能導致遞歸死鎖（AA死鎖）。

（2）不能以不同順序獲取兩個鎖類，否則導致AB-BA死鎖。

（3）不允許在獲取硬中斷安全的鎖類之后獲取硬中斷不安全的鎖類。

（4）不允許在獲取軟中斷安全的鎖類之后獲取軟中斷不安全的鎖類。

6、輸出分析

#ifconfigwlan0up[152.765951][152.767477]============================================[152.772802]WARNING:possiblerecursivelockingdetected[152.778130]4.19.123#4Tainted:GO[152.783021]--------------------------------------------[152.788347]ifconfig/231istryingtoacquirelock:[152.793243]c043f769(pmutex){+.+.},at:phy_RFSerialRead_8723D+0x30/0x168[8723ds]ctimer:152793251832,htime:152765938707,wtime:000000000000[152.807243][152.807243]buttaskisalreadyholdinglock:[152.813093]97637552(pmutex){+.+.},at:netdev_open+0x64/0xb0[8723ds]ctimer:152813101541,htime:151310817588,wtime:000000000000[152.825872][152.825872]otherinfothatmighthelpusdebugthis:[152.832415]Possibleunsafelockingscenario:[152.832415][152.838349]CPU0[152.840810]----[152.843269]lock(pmutex);[152.846082]lock(pmutex);[152.848894][152.848894]***DEADLOCK***[152.848894][152.854831]Maybeduetomissinglocknestingnotation[152.854831][152.861637]2locksheldbyifconfig/231:[152.865659]#0:cdd640ad(rtnl_mutex){+.+.},at:devinet_ioctl+0x118/0x5f8ctimer:152865670624,htime:151310702505,wtime:000000000000[152.877865]#1:97637552(pmutex){+.+.},at:netdev_open+0x64/0xb0[8723ds]ctimer:152877875915,htime:151310817588,wtime:000000000000[152.891057][152.891057]stackbacktrace:[152.895439]CPU:1PID:231Comm:ifconfigTainted:GO4.19.123#4[152.903022]Hardwarename:arobotr8family[152.907245][](unwind_backtrace)from[](show_stack+0x10/0x14)[152.915018][](show_stack)from[](dump_stack+0xa4/0xd8)[152.922268][](dump_stack)from[](__lock_acquire+0x1218/0x129c)[152.930209][](__lock_acquire)from[](lock_acquire+0x150/0x240)[152.938151][](lock_acquire)from[](__mutex_lock+0x7c/0x890)[152.945833][](__mutex_lock)from[](mutex_lock_interruptible_nested+0x18/0x20)[152.955975][](mutex_lock_interruptible_nested)from[](phy_RFSerialRead_8723D+0x30/0x168[8723ds])[152.968687][](phy_RFSerialRead_8723D[8723ds])from[](PHY_QueryRFReg_8723D+0xc/0x24[8723ds])[152.981030][](PHY_QueryRFReg_8723D[8723ds])from[](rtl8723ds_hal_init+0x28c/0x864[8723ds])[152.993294][](rtl8723ds_hal_init[8723ds])from[](rtw_hal_init+0x30/0x144[8723ds])[153.004763][](rtw_hal_init[8723ds])from[](_netdev_open+0x8c/0x290[8723ds])[153.015713][](_netdev_open[8723ds])from[](netdev_open+0x7c/0xb0[8723ds])[153.025646][](netdev_open[8723ds])from[](__dev_open+0x7c/0xc8)[153.033766][](__dev_open)from[](__dev_change_flags+0x148/0x15c)[153.041878][](__dev_change_flags)from[](dev_change_flags+0x18/0x48)[153.050339][](dev_change_flags)from[](devinet_ioctl+0x304/0x5f8)[153.058539][](devinet_ioctl)from[](inet_ioctl+0x278/0x350)[153.066222][](inet_ioctl)from[](sock_ioctl+0x190/0x50c)[153.073647][](sock_ioctl)from[](vfs_ioctl+0x28/0x3c)[153.080808][](vfs_ioctl)from[](do_vfs_ioctl+0x98/0x96c)[153.088229][](do_vfs_ioctl)from[](ksys_ioctl+0x38/0x54)[153.095650][](ksys_ioctl)from[](ret_fast_syscall+0x0/0x28)[153.103321]Exceptionstack(0xc67f7fa8to0xc67f7ff0)[153.108395]7fa0:000a88e2bef753480000000300008914bef75348000a88e2[153.116594]7fc0:000a88e2bef75348000946d000000036bef7550cbef75508bef7570d00000000[153.124788]7fe0:000c72e4bef752e40001b528b6e59166[153.130116]

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