Re: Which process is associated with process ID 0 (swapper)

["linux-os \(Dick Johnson\)" <linux-os@analogic.com>]

On Thu, 20 Apr 2006, Mikado wrote:

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>
> When a process make a connection to one server, if the server doesn't
> respond, the swapper process (PID 0) will re-send SYN packet
> automatically. How can I know which socket/process that re-sent SYN
> packet belongs to.
>
> Thanks in advance,
> Mikado.

This must be a trick question. Linux is not VAX/VMS. There is no
swapper process. Check in /proc. Processes start at 1. Even
kernel threads have PIDs greater than 1.

Portions of the kernel networking code operate detached. The code
gets the CPU from a timer queue or from an interrupt. When an
connection is attempted, the process attempting the connection
is either waiting, with its CPU time being used, or put to
sleep, while the timer queue's CPU time is being used. The
SYN/ACK handshake is handled during this time, therefore it
is possible to find who is attempting that connection. Netstat
gets that information from /proc/net and multiple socket
calls.

Cheers,
Dick Johnson
Penguin : Linux version 2.6.16.4 on an i686 machine (5592.89 BogoMips).
Warning : 98.36% of all statistics are fiction, book release in April.
_


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