tonyc

Using strace and lsof to debug blocked processes

You can use strace on a specific pid to figure out what a specific process is doing, e.g.:

strace -fp <pid>

You might see something like:

select(9, [3 5 8], [], [], {0, 999999}) = 0 (Timeout)

doug65536

Writing 16 bit value 0xbbaa (ByteCount = 2) at various offsets

+-----------------------------------+---------------------------------------------------------+
|                 DW                |                                                         |
+--------+--------+--------+--------+-------------+-------------------------------------------+
+ byte 3 | byte 2 | byte 1 | byte 0 | Address & 3 | ((LowerAddress & 3) + ByteCount + 3) >> 2 |
+--------+--------+--------+--------+-------------+-------------------------------------------+
|        |        |   bb   |   aa   |     0       | ((0 & 3) + (2 + 3)) >> 2 = 5 / 4 = 1      |
|        |        |        |        |             |                                           |

jlblancoc

Run the following in the terminal:

Install the gcc-7 packages:

sudo apt-get install -y software-properties-common
sudo add-apt-repository ppa:ubuntu-toolchain-r/test
sudo apt update
sudo apt install g++-7 -y

Set it up so the symbolic links gcc, g++ point to the newer version: