Deadlock of the process tree when running make
Brian Inglis
Brian.Inglis@SystematicSw.ab.ca
Thu Apr 7 23:54:33 GMT 2022
On 2022-04-07 15:53, Alexey Izbyshev wrote:
> I'm using 32-bit Cygwin 3.3.4 on 64-bit Windows 10 21H2. When running
> parallel make (for testing my project), very rarely I get the whole
> process tree hanging at some seemingly random point. An example of such
> a tree:
>
> make-+-make-+-bash---find
> | |-bash---find
> | |-bash---find
> | |-bash---find
> | |-bash---find
> | `-bash---javac
> `-make-+-bash---bash---bash---readlink
> `-bash---bash---bash-+-grep
> `-grep
>
> (In the above tree, javac is the zombie parent of a native javac, and
> the latter doesn't exist at this point).
>
> I got such hang two times while running make in a loop for several days.
> ProcessHacker shows that all leaf processes are single-threaded and are
> stuck on WaitForSingleObject().
>
> I've skimmed git log of cygwin-3_3-branch after cygwin-3_3_4-release,
> but couldn't find anything that seems definitely related.
>
> Has anybody seen something like this?
>
> Is there any way I can get useful data for diagnosing this hang from the
> process tree that I currently have hanging (I'm going to keep it for
> now)? Otherwise, what would be the best strategy?
I've seen infinite loops with readlink in build scripts under Cygwin.
Seeing that readlink in a process tree makes me suspicious that
something in a shell script is looping because two paths never match or
always match under Cygwin.
Often there is one constant path and a varying path which is subjected
to readlink in a loop.
Under Cygwin, you may have to pass the first path through readlink and
compare that resulting path against the varying value.
--
Take care. Thanks, Brian Inglis, Calgary, Alberta, Canada
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