vladak

xrandr --addmode DP-2 1440x900

vladak

What is OpenGrok

• blindingly fast source code search and cross-reference engine
  • can be used for searching and source code browsing
  • “grok” = profoundly understand
    • in our case, source code
• the IP/project is still owned by Oracle
  • developed as open source (CDDL license)
• Searching computer programs that use different semantics
• written in Java/JSP
• originally developed as a tool perform security vulnerability research quickly

vladak

Sources

• https://development.robinwinslow.uk/2016/06/23/fix-docker-networking-dns/
• https://crondev.com/running-docker-behind-proxy/

Install

Per https://www.digitalocean.com/community/tutorials/how-to-install-and-use-docker-on-ubuntu-20-04

vladak

Service management

• temporary: sudo service stop mydesktop
• permanent: sudo systemctl disable mydesktop

DNS servers debugging

• get local DNS server address: cat /etc/resolv.conf
• get list of DNS servers: netplan get all
• show who is listening on port 53 netstat -peanut (without lsof)

vladak

- mysh: go through detailed task description
  - can start coding right away (parsing), do not have to wait until fork()/pipe()/exec() are explained
  - the shell cannot (and should not) be coded in couple of days
    - write your own unit tests
    
- demonstrate how to use Github+Travis
  .travis.yml:
  language: c
  compiler:
  - clang

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- notable features/changes in 1.1:
  - RESTful API
  - Python scripts
  - indexer parallelization
  - Suggester (Adam Hornacek's master thesis)
  - new highlighter
  - LOC column
  - no packages anymore
  - Search CLI EOF
  - project centric approach

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foo

    +--------+
    |        |
    +--------+

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tasks:
  - rewrite queue-simulation.c to use RW locks
    - add another thread that will print the number of items
      in the queue less frequently than the main thread
  - run atomic-add in multiple modes, compare the results
  - write pthread_barrier impl
    - start with phtread_barrier_t, pthread_barrier_wait()
  - rewrite semaphores/posix-sem-fixed-race.c to use unnamed
    semaphores. Are they kernel persistent ?

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- signals and threads (*go through the slide first*):
  - create process with N threads
  - see if sending a signal to the whole process with multiple threads will deliver the signal to
    different threads (perform various activities in the threads - I/O, CPU intensive, mix of both, ...)

- define a foo_t type as structure with a reference count and implement 2 macros:
  FOO_REHOLD - bumps the refcount
  FOO_REFRELE - decrement the refcount and if 0, call foo_free()
                that will de-initialize the data structure
  - implement negative unit test

vladak

- finish the sleep -> join (thread num in argv[1]) task
- write a simple program that creates couple of threads, each doing a number arithm ops
  - after random number of the ops, the thread SIGSEGV's, observe the result
    - compile with debug flags, see if gdb can display stacks of all threads at the moment of crash
- write simple program with 2 thread types - one sleeping in syscall, another looping and printing to stdout
  - create more than 1 thread of each type
  - the threads doing syscals can e.g. pick a random file from /etc directory, open it and read it
  - each thread will write its own thread ID to stdout once running
  - goal: see if the other threads run while another sleeps in syscall
  - see if truss/strace can display thread IDs