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| <== Date ==> | <== Thread ==> |
|---|
| Subject: | Re: deadlock in pcas 3.14.12.6-rc1 |
| From: | Wang Xiaoqiang <[email protected]> |
| To: | Bruce Hill <[email protected]>, "[email protected]" <[email protected]> |
| Date: | Wed, 7 Dec 2016 12:08:21 +0100 |
Hi Bruce, Thanks. The crash cannot be reproduced with this fix. Since the casPVI lock is now acquire during channel creation,just a purely theoretical thinking, is there a chance that the deadlock would happen if a new CA client wants to connect while PCAS application is calling postEvent?
I am running the same test again, and in addition four loops to make continuous caget requests.
$ while [ 1 ]; do caget MTEST:MinValue; done; Best Xiaoqiang On 12/07/2016 10:45 AM, Bruce Hill wrote:
Hi Xiaoqiang, Thanks, I was able to reproduce the bug using your suggestions. I've submitted a proposed fix on launchpad. Please let me know if you have a chance to try it. My version ran all day today w/o crashing. https://code.launchpad.net/~bhill/epics-base/pcas-deadlock-fix-3.14/+merge/312638 <https://code.launchpad.net/%7Ebhill/epics-base/pcas-deadlock-fix-3.14/+merge/312638> Cheers, - Bruce On 12/6/2016 1:38 AM, Wang Xiaoqiang (PSI) wrote:Hi Bruce, I replied you here https://github.com/paulscherrerinstitute/pcaspy/issues/29#issuecomment-265103000 I carried out the described test procedure on a SL6 64bit Linux PC. The problem appears definitely in a few seconds. Best Xiaoqiang -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Bruce Hill Sent: Dienstag, 6. Dezember 2016 04:15 To: [email protected] Subject: Re: deadlock in pcas 3.14.12.6-rc1 Hi Xiaoqiang, Do you have a pcaspy example that I can run to reproduce this? I'm running pcaspy 0.6.2 currently, but could also build from a github branch if available. Thanks, - Bruce On 11/10/2016 08:59 AM, Wang Xiaoqiang (PSI) wrote:Hi, I am testing the support of dynamic array in the recent base 3.14.12.6-rc1. Using a normal pcaspy application, which updates ~15 Hz. It repeatedly gets into a deadlock state. The analysis has been put up here https://github.com/paulscherrerinstitute/pcaspy/issues/29 The solution could be reversing the lock order during casEventSys::process. But it does not seem to be easy, because the chain of calls involved. Best Xiaoqiang-- Bruce Hill Member Technical Staff SLAC National Accelerator Lab 2575 Sand Hill Road M/S 10 Menlo Park, CA 94025