Re: [RFC, PATCH] cond_resched() added to close_files()

[Eric Dumazet]

Ingo Molnar a écrit :
> * Andrew Morton <akpm@xxxxxxxx> wrote:
>
>   
> > Makes my machine hang early during the startup of init.
> >
> > The last process to pass through close_file() is `hostname', presuably 
> > parented by init.  `hostname' exits then everything stops.  init is 
> > left sleeping in select().
> >
> > All very strange.
> >     
>
> weird. This really shouldnt cause a hang - i think there must be a bug 
> hiding elsewhere, this cond_resched() ought to be fine.
>
> 	Ingo
>
>   
Maybe a process is now awaken because of a closed pipe, instead of a SIGCHLD

Process A, father/parent of process B. They share a pipe (A reads the 
pipe, B writes to)

Before

Process B exits, "atomically close all of its files and sending a SIGCLD 
to its parent"
Process A catch the SIGCLD.

After :
Process B exits "close its files (and the pipe), reschedule before final 
SIGCLD"
Process A gets the POLLIN/POLLHUP indication on the pipe -> Another code 
path is run and may trigger a user side bug ?


Eric




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