Re: Hang / zombie process from Xarray page-fault conversion (bisected)
On Thu, Mar 07, 2019 at 10:16:17PM -0800, Dan Williams wrote:
Hi Willy,
We're seeing a case where RocksDB hangs and becomes defunct when
trying to kill the process. v4.19 succeeds and v4.20 fails. Robert was
able to bisect this to commit b15cd800682f "dax: Convert page fault
handlers to XArray".
I see some direct usage of xa_index and wonder if there are some more
pmd fixups to do?
Other thoughts?
I don't see why killing a process would have much to do with PMD
misalignment. The symptoms (hanging on a signal) smell much more like
leaving a locked entry in the tree. Is this easy to reproduce? Can you
get /proc/$pid/stack for a hung task?