Unix – Kernel: Dealing with deadlocks in unix

deadlocklinux-kernelunix

A deadlock would occur if process 1 locks resource A and waits for
resource B, while simultaneously (due to context switches at the "right" places) process 2 locks resource B and waits for access to resource
A.

How does Unix deal with such deadlocks? I read the following here.

Many deadlocks can be prevented by simply requiring all processes that
lock multiple resources to lock them in the same order (e.g.,
alphabetically by lock name)

How can it change the order in which locks are acquired without also changing the execution order?
Could someone detail the approach to deadlock-handling taken by the modern Unix kernel?

Best Answer

For Linux kernel, it does NOT handle this, because it has no idea on how to fix it. Instead, it detects this kind of deadlock at runtime and complains.

The technology it uses is lockdep, which is a runtime locking correctness validator, for details, please take a look at kernel document Documentation/lockdep-design.txt.

Related Solutions

Unix shell script find out which directory the script file resides

In Bash, you should get what you need like this:

#!/usr/bin/env bash

BASEDIR=$(dirname "$0")
echo "$BASEDIR"

C# – How to convert a Unix timestamp to DateTime and vice versa

Here's what you need:

public static DateTime UnixTimeStampToDateTime( double unixTimeStamp )
{
    // Unix timestamp is seconds past epoch
    DateTime dateTime = new DateTime(1970, 1, 1, 0, 0, 0, 0, DateTimeKind.Utc);
    dateTime = dateTime.AddSeconds( unixTimeStamp ).ToLocalTime();
    return dateTime;
}

Or, for Java (which is different because the timestamp is in milliseconds, not seconds):

public static DateTime JavaTimeStampToDateTime( double javaTimeStamp )
{
    // Java timestamp is milliseconds past epoch
    DateTime dateTime = new DateTime(1970, 1, 1, 0, 0, 0, 0, DateTimeKind.Utc);
    dateTime = dateTime.AddMilliseconds( javaTimeStamp ).ToLocalTime();
    return dateTime;
}

Best Answer

Related Solutions

Unix shell script find out which directory the script file resides

C# – How to convert a Unix timestamp to DateTime and vice versa

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