Messages in this thread | | | Date | Tue, 5 Jul 2022 15:34:03 -0400 | Subject | Re: [PATCH 04/13] locking/qspinlock: move pv lock word helpers into qspinlock.c | From | Waiman Long <> |
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On 7/4/22 10:38, Nicholas Piggin wrote: > There is no real reason not to keep all the bit manipulation together. > > Signed-off-by: Nicholas Piggin <npiggin@gmail.com> > --- > kernel/locking/qspinlock.c | 107 ++++++++++++++++------------ > kernel/locking/qspinlock_paravirt.h | 51 ------------- > 2 files changed, 63 insertions(+), 95 deletions(-) > > diff --git a/kernel/locking/qspinlock.c b/kernel/locking/qspinlock.c > index 7360d643de29..8f2173e22479 100644 > --- a/kernel/locking/qspinlock.c > +++ b/kernel/locking/qspinlock.c > @@ -141,7 +141,24 @@ struct qnode *grab_qnode(struct qnode *base, int idx) > > #define _Q_LOCKED_PENDING_MASK (_Q_LOCKED_MASK | _Q_PENDING_MASK) > > +/** > + * set_pending - set the pending bit. > + * @lock: Pointer to queued spinlock structure > + * > + * *,0,* -> *,1,* > + * > + * The pending bit is used by the queue head vCPU to indicate that it > + * is actively spinning on the lock and no lock stealing is allowed.
The pending bit has different usage in pv and non-pv cases. The description here refers to the pv case. For non-pv, it is used to avoid loading the the extra node cacheline in likely contended case.
Cheers, Longman
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