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Hello,<br>
<br>
Currently, on LBUG, Lustre tries to call a usermode helper at
'/usr/lib/lustre/lnet_upcall'. This is for some sort of binary that
a user would like executed before the LBUG itself (by default, a
panic) happens. Lustre does not include an lnet_upcall script, so
by default, the call fails.<br>
<br>
Unfortunately, in extremely low memory situations, the attempt to
make this call can hang, resulting in a node which is in an invalid
state but will not actually panic. This is quite problematic as it
can, for example, prevent failover or dump collection (for debugging
purposes), depending on how a system is configured.<br>
<br>
<a href="https://jira.hpdd.intel.com/browse/LU-8418">LU-8418</a>
(from Alexander Zarochentsev) is looking to disable this by
default. As Andreas Dilger pointed out in the patch review
(<a class="moz-txt-link-freetext" href="http://review.whamcloud.com/#/c/21440/">http://review.whamcloud.com/#/c/21440/</a>), this would break any
existing users who had put their script in that location.<br>
<br>
But I suspect no one is actually using this feature.<br>
<br>
So:<br>
Do you use (or know of anyone using) the lnet_upcall feature to call
a binary before LBUG? (I'm looking for end user uses; if a
developer is using it, I think it's reasonable to ask them to set it
manually.)<br>
<br>
- Patrick<br>
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