Synchronous Message Passing; Blocked Processes And Process States - Cisco CRS-1 - Carrier Routing System Router Troubleshooting Manual

Chapter 8 Process Monitoring and Troubleshooting
The process ospf is given a Job ID of 250. This Job ID never changes on a running router. Within the
ospf process there are 7 threads, each with their own Thread ID or TID. For each thread, the stack space
for each thread, the priority of each thread, and the thread state is listed.
The PID is 299228. This number changes each time the process is restarted. The Respawn count
indicates how many times the process has restarted and the Process state should show the RUN state.

Synchronous Message Passing

The message passing life cycle is as follows:
1.
2.
3.
4.
5.
This blocking client-server model is synchronous message passing. This means the client sends a
message and blocks. The server receives the message, processes it, replies back to the client, and then
the client unblocks. The specific details are as follows.
1.
2.
3.
4.
5.
6.
7.
8.
Use the show processes command to display the states the client and servers are in.
thread states.

Blocked Processes and Process States

Use the show processes blocked command to display the processes that are in blocked state.
Synchronized message passing enables you to track the life cycle of inter-process communication
between the different threads. At any point in time a thread can be in a specific state. A blocked state can
be a symptom of a problem. This does not mean that if a thread is in blocked state then there is a
problem—blocked threads are normal. Using the show processes blocked command is sometimes a
good way to start troubleshooting operating system-type problems. If there is a problem, for example the
CPU is high, then use the show processes blocked command to determine if anything looks abnormal
(what is not normal for your functioning router). This provides a baseline for you to use as a comparison
when troubleshooting process life cycles.
At any point in a time a thread can be in a particular state.
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A server creates a message channel.
A client connects to a channel of a server (analogous to posix open).
A client sends a message to a server (MsgSend) and waits for a reply and blocks.
The server receives (MsgReceive) a message from a client, processes the message and replies to the
client.
The client unblocks and processes the reply from the server.
Server is waiting in RECEIVE state
Client sends a message to the server and becomes BLOCKED
Server receives the message and unblocks (if waiting in receive state)
Client moves to the REPLY state
Server moves to the RUNNING state
Server processes the message
Server replies to the client
Client unblocks
Table 8-1
Cisco IOS XR Troubleshooting Guide for the Cisco CRS-1 Router
Process States
Table 8-1 lists the thread states.
Table 8-1 lists the
lists the thread states.
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