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through the lock-switching hoops. A few of the INP lookup operations that lock INPs after the lookup do so using this mechanism (to maintain lock ordering): 1. Lock lookup structure. 2. Find INP. 3. Acquire reference on INP. 4. Drop lock on lookup structure. 5. Acquire INP lock. 6. Drop reference on INP. This change provides a slightly shorter path for cases where the INP lock is uncontested: 1. Lock lookup structure. 2. Find INP. 3. Try to acquire the INP lock. 4. If successful, drop lock on lookup structure. Of course, if the INP lock is contested, the functions will need to revert to the previous way of switching locks safely. This saves a few atomic operations when the INP lock is uncontested. Discussed with: gallatin, rrs, rwatson MFC after: 2 weeks Sponsored by: Netflix, Inc. Differential Revision: https://reviews.freebsd.org/D12911