[bitbake-devel] [PATCH 1/1] bitbake: cooker: Kill alive process before join it

[Robert Yang]

Hi Larson,

On 8/22/19 10:14 PM, Christopher Larson wrote:
> Looks like you’re partially duplicating what the ‘force’ logic does already, but 
> for the non-force case as well, yes? process.terminate() sounds a lot like 
> sending a SIGTERM, though admittedly I haven’t read the code to Process 
> recently. Perhaps if this is truly necessary, the logic can be simplified.


The process.join(.1) may also hang if the result_queue is not NULL, but AFAIK ,
this only happens when KeyboardInterrupt or Failed to parse a recipe, so I think
that 'force' shutdown's process.jion(.1) won't hang, and I didn't see it hangs
in the "force" code, we may have another way to make it better, check
result_queue._wlock, but the _wlock is an internal variable, so I gave it up and
just use os.kill() to avoid the hang problem completely, but there might be
side effects that I didn't know?

// Robert

> On Aug 22, 2019, 12:10 AM -0700, Robert Yang <liezhi.yang at windriver.com>, wrote:
>> Fixed:
>> $ echo helloworld >> meta/recipes-extended/bash/bash_4.4.18.bb
>> $ while true; do kill-bb; rm -fr bitbake-cookerdaemon.log 
>> tmp/cache/default-glibc/qemux86-64/x86_64/bb_cache.dat* ; bitbake -p; done
>>
>> It may hang in 10 mins, there are two problems:
>> * There might be deadlocks when call process.join() if the queue is not NULL,
>> so we need cleanup the queue before join() it, but:
>> * The self.result_queue.get(timeout=0.25) may hang if the queue._wlock is hold
>> by SomeOtherProcess, the queue has the following info when it hangs:
>> '_wlock': <Lock(owner=SomeOtherProcess)>, so that we may can't clean up the
>> queue.
>>
>> We can kill alvie process before join it to fix the problems.
>>
>> Signed-off-by: Robert Yang <liezhi.yang at windriver.com>
>> ---
>> bitbake/lib/bb/cooker.py | 12 ++++--------
>> 1 file changed, 4 insertions(+), 8 deletions(-)
>>
>> diff --git a/bitbake/lib/bb/cooker.py b/bitbake/lib/bb/cooker.py
>> index 0607fcc..e42bcba 100644
>> --- a/bitbake/lib/bb/cooker.py
>> +++ b/bitbake/lib/bb/cooker.py
>> @@ -2082,19 +2082,15 @@ class CookerParser(object):
>> for process in self.processes:
>> self.parser_quit.put(None)
>>
>> - # Cleanup the queue before call process.join(), otherwise there might be
>> - # deadlocks.
>> - while True:
>> - try:
>> - self.result_queue.get(timeout=0.25)
>> - except queue.Empty:
>> - break
>> -
>> for process in self.processes:
>> if force:
>> process.join(.1)
>> process.terminate()
>> else:
>> + # Kill the alive process firstly before join() it to avoid
>> + # deadlocks
>> + if process.is_alive():
>> + os.kill(process.pid, 9)
>> process.join()
>>
>> sync = threading.Thread(target=self.bb_cache.sync)
>> --
>> 2.7.4
>>
>> --
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