Re: [RFC] new syscall to allow notification when arbitrary pids die

[Chris Friesen]

Muli Ben-Yehuda wrote:
> On Sat, May 10, 2003 at 02:29:54AM -0400, Chris Friesen wrote:
> 
> 
>>I see two immediate uses for this.  One would be to enable a "watcher" 
>>process which can do useful things on the death of processes which 
>>registered with it (logging, respawning, notifying other processes,
>>etc).  
>>
> 
> Do it from user space, kill(pid, 0), check for ESRCH. I might see the
> benefit of a new system call if it was synchronous (wait() semantics),
> but since signal delivery is asynch anyway.... 

Exactly.  I don't want to explicitly poll each process being monitored to see if 
it is still alive.  That solution doesn't scale well--what happens when you are 
monitoring 5000 processes and you want to make sure that you catch them within a 
certain amount of time?  You end up spending a lot of cpu time doing the monitoring.

> There's already a well established way to do what you want (get
> non-immediate notification of process death). What benefit would your
> approach give? 

Its cheaper and faster.  It only costs a single call for each process, and then 
you get notified immediately when it dies.

Chris

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