In the Linux world, pid means two things. It’s the id of a process from POSIX’s point of view and the id of a task from kernel’s point of view.

1. Get Java GC Related Application Stopped Time

Hit a Linux kernel bug that read() returns wrong data if it crosses a hugepage boundary.

我说我喜欢你的歌，我不知道这算不算是一件好事。 我说我喜欢你的词，总是道出我心中不欲人知的事。

SSH asks me to go way because of ntp clock skew

在南京大学软件学院读完本科后我到CMU读了硕士。虽然在CMU只有短短的一年半时间，但我还是从多个方面体验到了CMU（美国）的计算机教育。这其中有很多东西值得国内的高校学习借鉴。

Last semester, I took the course 15410 and wrote a kernel from scratch with my partner. I learned a lot from this course and the kernel project. Following is what I have learned:

1. Never Failed Functions
2. Comment on Why
3. Synchronization
4. Error Handling
5. Why Writing a Kernel From Scratch
6. Misc.

Imagine that you launch a singleTop activity using intent A and then launch it again using intent B. As a result, activity’s onNewIntent method is called and inside this method you call setIntent to store the new intent. After that, Android decides to relaunch the activity. Now we have the question: which intent will you get after Android relaunches the activity? The original one(A) or the latest one(B)?

Send an android.os.Message whose what is 0 and then remove it, which unexpectedly removes all posted Runnables

SSL(Secure Sockets Layer)是目前广泛用来加密网络通信的加密协议。它的一个著名应用就是HTTPS，也就是使用SSL协议对HTTP进行加密从而使得整个通信更加安全。对于一个移动应用（其他类型的客户端也同理），为了保证其和服务器的通信安全，开发者就会使用SSL来加密客户端和服务器之间的通信。这样理应是安全的，但由于很多开发者使用方式不对，导致客户端和服务器之间的SSL通信会受到中间人攻击(Man-in-the-middle attack)，从而使得安全性荡然无存。本文将首先介绍下SSL和中间人攻击的原理，然后会提供一个中间人攻击的实例，最后本文介绍该如何防止中间人攻击。