Reading subprocess stdout susceptible to deadlock

[Vitaly Davidovich]

Hi Roger,

The stack traces are:

"process reaper" #44 daemon prio=10 os_prio=0 tid=0x0000000004083000
nid=0x7b1c waiting for monitor entry [0x00002b703ffbe000]

   java.lang.Thread.State: BLOCKED (on object monitor)

        at java.lang.UNIXProcess$ProcessPipeInputStream.processExited(UNIXProcess.java:528)

        - waiting to lock <0x00000000aba7a790> (a
java.lang.UNIXProcess$ProcessPipeInputStream)

        at java.lang.UNIXProcess.lambda$initStreams$275(UNIXProcess.java:299)

        at java.lang.UNIXProcess$$Lambda$10/523574157.run(Unknown Source)

        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)





"pool-1-thread-1" #43 prio=5 os_prio=0 tid=0x0000000003ee3800
nid=0x7b13 runnable [0x00002b7050837000]

   java.lang.Thread.State: RUNNABLE

        at java.io.FileInputStream.readBytes(Native Method)

        at java.io.FileInputStream.read(FileInputStream.java:255)

        at java.io.BufferedInputStream.fill(BufferedInputStream.java:246)

        at java.io.BufferedInputStream.read1(BufferedInputStream.java:286)

        at java.io.BufferedInputStream.read(BufferedInputStream.java:345)

        - locked <0x00000000aba7a790> (a
java.lang.UNIXProcess$ProcessPipeInputStream)

        at SomeClass.callReadOnInputStream()


SomeClass.callReadOnInputStream() is something that invokes
InputStream.read(byte[], int, int) on the stream.

Thanks


On Wed, Mar 30, 2016 at 10:09 AM, Roger Riggs <Roger.Riggs at oracle.com>
wrote:

> Hi Vitaly,
>
> I haven't seen that before, please create a bug and include the stack
> traces.
>
> Thanks, Roger
>
>
>
> On 3/30/2016 9:56 AM, Vitaly Davidovich wrote:
>
>> Hi,
>>
>> It seems that doing a blocking read on a subprocess's stdout can lead to
>> deadlock between the thread doing the read and the process reaper thread.
>> The deadlock occurs because the reader is synchronized on the
>> ProcessPipeInputStream, blocks for more data to consume, and process
>> reaper
>> comes along trying to call processExited, which also synchronizes on the
>> same PPIS.  The reader appears stuck because it's not seeing the EOF due
>> to
>> process reaper not being able to close the stream.
>>
>> I couldn't find any existing reports of this via quick search, which makes
>> me wonder if I'm missing something.  Is this a known issue?
>>
>> Thanks
>>
>>
>>
>