Messages in this thread | | | Subject | Re: [RFC PATCH] scsi: libsas: fix WARN on device removal | From | John Garry <> | Date | Fri, 11 Nov 2016 08:23:40 +0000 |
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On 11/11/2016 08:12, wangyijing wrote: >> >> They're not the same. I don't see how your solution properly deals with remote sas_port deletion. >> >> When we unplug a device connected to an expander, can't the sas_port be deleted twice, in sas_unregister_devs_sas_addr() from domain revalidation and also now in sas_destruct_devices()? I think that this gives a NULL dereference. >> And we still get the WARN as the sas_port has still been deleted before the device. >> >> In my solution, we should always delete the sas_port after the attached device. >> >>>> >>>> i.e. it moves the port destruction to the workqueue and still suffers >>>> from the flutter problem: >>>> >>>> http://marc.info/?l=linux-scsi&m=143801026028006&w=2 >>>> http://marc.info/?l=linux-scsi&m=143801971131073&w=2 >>>> >>>> Perhaps we instead need to quiet this warning? >>>> >>>> http://marc.info/?l=linux-scsi&m=143802229932175&w=2 >> >> I have not seen the flutter issue. I am just trying to solve the horrible WARN dump. >> However I do understand that there may be a issue related to how we queue the events; there was a recent attempt to fix this, but it came to nothing: >> https://www.spinics.net/lists/linux-scsi/msg99991.html > > We found libsas hotplug several problems: > 1. sysfs warning calltrace(like the case you found);
Maybe you can then review my patch.
> 2. hot-add and hot-remove work events may process out of order; > 3. in some extreme cases, libsas may miss some events, if the same event is still pending in workqueue. >
Can you tell me how to recreate #2 and #3?
> It's a complex issue, we posted two patches, try to fix these issues, but now few people are interested in it :( >
IIRC, you sent as RFC and got a "reviewed-by" from Hannes, so I'm not sure what else you want. BTW, I thought that the changes were quite drastic.
John
>> >>> >>> Alternatively we need a mechanism to cancel in-flight port shutdown >>> requests when we start re-attaching devices before queued port >>> destruction events have run. >>> >>> . >>> >> >> >> _______________________________________________ >> linuxarm mailing list >> linuxarm@huawei.com >> http://rnd-openeuler.huawei.com/mailman/listinfo/linuxarm >> >> . >> > > > . >
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