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Waiman Long
a23db284fe
Provide a separate (second) version of the spin_lock_slowpath for paravirt along with a special unlock path. The second slowpath is generated by adding a few pv hooks to the normal slowpath, but where those will compile away for the native case, they expand into special wait/wake code for the pv version. The actual MCS queue can use extra storage in the mcs_nodes[] array to keep track of state and therefore uses directed wakeups. The head contender has no such storage directly visible to the unlocker. So the unlocker searches a hash table with open addressing using a simple binary Galois linear feedback shift register. Suggested-by: Peter Zijlstra (Intel) <[email protected]> Signed-off-by: Waiman Long <[email protected]> Signed-off-by: Peter Zijlstra (Intel) <[email protected]> Cc: Andrew Morton <[email protected]> Cc: Boris Ostrovsky <[email protected]> Cc: Borislav Petkov <[email protected]> Cc: Daniel J Blueman <[email protected]> Cc: David Vrabel <[email protected]> Cc: Douglas Hatch <[email protected]> Cc: H. Peter Anvin <[email protected]> Cc: Konrad Rzeszutek Wilk <[email protected]> Cc: Linus Torvalds <[email protected]> Cc: Oleg Nesterov <[email protected]> Cc: Paolo Bonzini <[email protected]> Cc: Paul E. McKenney <[email protected]> Cc: Peter Zijlstra <[email protected]> Cc: Raghavendra K T <[email protected]> Cc: Rik van Riel <[email protected]> Cc: Scott J Norton <[email protected]> Cc: Thomas Gleixner <[email protected]> Link: http://lkml.kernel.org/r/[email protected] Signed-off-by: Ingo Molnar <[email protected]>