bug#17561: Emacs can forget processes

[Paul Eggert]

Jorgen Schaefer wrote:

> > Can you run the shell command 'strace -p' on an Emacs with the
> > problem, and trace the system calls near the offending area?
>
> The bug report includes an strace output. Emacs does the pselect6 call

Sorry, I should have been more specific.  It'd be nice to see the strace 
output for when you run start-process in a temp buffer, not for later 
when Emacs is in a tight loop.

> read(2) returning 0 indicates an EOF (which pselect6 indicates as
> waiting input), I suspect there could at least be a sanity check here
> to close the file descriptors instead of continuously polling.

Maybe, though I worry that might mask the bug and might cause other, 
more serious failures down the road.  It'd be nicer to fix the actual 
bug, if we can figure out what it is.

For what it's worth I tried reproducing the bug with emacs-24 'emacs -Q' 
on Fedora, using your recipe, but this didn't have a problem.  I ran it 
1000 times rapidly in sequence and it was OK.  I ran it 10000 times and 
ran out of file descriptors but that's to be expected.