proc_loadavg: fix ABBA deadlock between read/refresh #606
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Idea of this fix is to always take nested locks in the same order. At the same time, we adding an extra check to insert_node() that prevents adding a new load_node with the same cgroup (->cg field) value. This is theoretically possible because we don't hold .rilock/.lock when we call insert_node(). It looks like we have this issue from the initial implementation of loadavg virtualization and it's hardly reproducible that's why we weren't able to notice it. Fixes: lxc#605 Signed-off-by: Alexander Mikhalitsyn <[email protected]>
brauner
approved these changes
Aug 10, 2023
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Idea of this fix is to always take nested locks in the same order.
At the same time, we adding an extra check to insert_node() that prevents adding a new load_node with the same cgroup (->cg field) value. This is theoretically possible because we don't hold .rilock/.lock when we call insert_node().
It looks like we have this issue from the initial
implementation of loadavg virtualization and it's hardly reproducible that's why we weren't able to notice it.
Fixes: #605