How to check if a process is in hang state Linux

Question

Is there any command in Linux through which i can know if the process is in hang state

User · Answer

What do you mean by    hang state     Typically  a process that is unresponsive and using 100  of a CPU is stuck in an endless loop  But there s no way to determine whether that has happened or whether the process might not eventually reach a loop exit state and carry on   Desktop hang detectors just work by sending a message to the application s event loop and seeing if there s any response  If there s not for a certain amount of time they decide the app has    hung       but it s entirely possible it was just doing something complicated and will come back to life in a moment once it s done  Anyhow  that s not something you can use for any arbitrary process

User · Answer

Unfortunately there is no hung state for a process  Now hung can be deadlock  This is block state  The threads in the process are blocked  The other things could be live lock where the process is running but doing the same thing again and again  This process is in running state  So as you can see there is no definite hung state   As suggested you can use the top command to see if the process is using 100  CPU or lot of memory

User · Answer

you could check the files   proc  pid  task  thread ids  status

User · Answer

Is there any command in Linux through which i can know if the process is in hang state    There is no command  but once I had to do a very dumb hack to accomplish something similar  I wrote a Perl script which periodically  every 30 seconds in my case     run ps to find list of PIDs of the watched processes  along with exec time  etc  loop over the PIDs start gdb attaching to the process using its PID  dumping stack trace from it using thread apply all where  detaching from the process a process was declared hung if    its stack trace didn t change and time didn t change after 3 checks its stack trace didn t change and time was indicating 100  CPU load after 3 checks  hung process was killed to give a chance for a monitoring application to restart the hung instance    But that was very very very very crude hack  done to reach an about-to-be-missed deadline and it was removed a few days later  after a fix for the buggy application was finally installed   Otherwise  as all other responders absolutely correctly commented  there is no way to find whether the process hung or not  simply because the hang might occur for way to many reasons  often bound to the application logic   The only way is for application itself being capable of indicating whether it is alive or not  Simplest way might be for example a periodic log message  I m alive

[linux] How to check if a process is in hang state (Linux)

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