Module Name: src Committed By: riastradh Date: Mon Mar 28 12:37:56 UTC 2022
Modified Files: src/sys/kern: vfs_vnode.c src/sys/miscfs/specfs: spec_vnops.c Log Message: specfs: Remove specnode from hash table in spec_node_revoke. Previously, it was possible for spec_node_lookup_by_dev to handle a speconde that a concurrent spec_node_destroy is about to remove from the hash table and then free, as soon as spec_node_lookup_by_dev releases device_lock. Now, the ordering is: 1. Remove specnode from hash table in spec_node_revoke. At this point, no _new_ vnode references are possible (other than possibly one acquired by vcache_vget under v_interlock), but there may be existing ones. 2. Mark vnode reclaimed so vcache_vget will fail. 3. The last vrele (or equivalent logic in vcache_vget) will then free the specnode in spec_node_destroy. This way, _if_ a thread in spec_node_lookup_by_dev finds a specnode in the hash table under device_lock/v_interlock, _then_ it will not be freed until the thread completes vcache_vget. This change requires calling spec_node_revoke unconditionally for device special nodes, not just for active ones. Might introduce slightly more contention on device_lock but not much because we already have to take it in this path anyway a little later in spec_node_destroy. To generate a diff of this commit: cvs rdiff -u -r1.140 -r1.141 src/sys/kern/vfs_vnode.c cvs rdiff -u -r1.208 -r1.209 src/sys/miscfs/specfs/spec_vnops.c Please note that diffs are not public domain; they are subject to the copyright notices on the relevant files.