100分请教高手一个死锁的问题

[karlzheng]

发现一个dead lock 的log如：
http://blog.csdn.net/zhengkarl/article/details/7718618
所示

感到不理解的是怎么看出存在下面的锁链：
&pch->upl --> &(&ppp->wlock)->rlock --> &(&mx_tty[i].tty_spinlock)->rlock

请高手解答。谢谢！

[Wenxy1]

/* 直接贴这些锁的代码。*/

[karlzheng]

[Quote=引用 1 楼 的回复:]
C/C++ code

/* 直接贴这些锁的代码。*/
[/Quote]
代码很多，连log在帖子上都放不下，只能放到blog上。

[morris88]

楼上说的很有道理

[morris88]

 {3}[  140.037940] pppd/2978 [HC0[0]:SC0[4]:HE1:SE0] is trying to acquire:
 {3}[  140.044336]  (&(&pch->downl)->rlock){+.....}, at: [<c025e2c4>] ppp_push+0x44/0xac
 {3}[  140.052062] and this task is already holding:
 {3}[  140.058394]  (&(&ppp->wlock)->rlock){+.....}, at: [<c025f078>] ppp_xmit_process+0x1c/0xac
 {3}[  140.066814] which would create a new lock dependency:
 {3}[  140.072099]  (&(&ppp->wlock)->rlock){+.....} -> (&(&pch->downl)->rlock){+.....}
 {3}[  140.157440] to a SOFTIRQ-READ-irq-unsafe lock:
 {3}[  140.163931]  (&(&mx_tty[i].tty_spinlock)->rlock){+.+...}
 {3}[  140.264185] Chain exists of:
 {3}[  140.264189]   &pch->upl --> &(&ppp->wlock)->rlock --> &(&mx_tty[i].tty_spinlock)->rlock
 {3}[  140.289362]        ----                    ----
 {3}[  140.294061]   lock(&(&mx_tty[i].tty_spinlock)->rlock);
 {3}[  140.305606]                                lock(&pch->upl);
 {3}[  140.311422]                                lock(&(&ppp->wlock)->rlock);
 {3}[  140.331370] 1 lock held by pppd/2978:
 {3}[  140.335204]  #0:  (&(&ppp->wlock)->rlock){+.....}, at: [<c025f078>] ppp_xmit_process+0x1c/0xac
 {3}[  140.819549] 
 {3}[  140.821286] -> (&(&ppp->wlock)->rlock){+.....} ops: 6 {
 {3}[  141.114411] the dependencies between the lock to be acquired and SOFTIRQ-READ-irq-unsafe lock:
 {3}[  141.125001]   -> (&(&mx_tty[i].tty_spinlock)->rlock){+.+...} ops: 516 {
 {3}[  141.639982] 
 {3}[  141.641718]  -> (&(&ap->xmit_lock)->rlock){+.....} ops: 6 {
 {3}[  141.932932] 
 {3}[  141.934665] -> (&(&pch->downl)->rlock){+.....} ops: 4 {

[karlzheng]

[Quote=引用 4 楼 的回复:]

PHP code
{3}[ 140.037940] pppd/2978 [HC0[0]:SC0[4]:HE1:SE0] is trying to acquire:
{3}[ 140.044336] (&(&pch->downl)->rlock){+.....}, at: [<c025e2c4>] ppp_push+0x44/0xac
{3}[ 140.052062……
[/Quote]

1 lock held by pppd/2978:
#0: (&(&ppp->wlock)->rlock){+.....}, at: [<c025f078>] ppp_xmit_process+0x1c/0xac
怎么样导致死锁？