On Thu, Jan 19, 2023 at 03:15:40PM +0100, Frederic Weisbecker wrote: > On Thu, Jan 19, 2023 at 03:11:35PM +0100, Frederic Weisbecker wrote: > > The state space of the GP sequence number isn't documented and the > > definitions of its special values are scattered. Try to gather some > > common knowledge near the GP seq headers. > > > > Signed-off-by: Frederic Weisbecker <frederic@xxxxxxxxxx> > > --- > > kernel/rcu/rcu.h | 33 +++++++++++++++++++++++++++++++++ > > 1 file changed, 33 insertions(+) > > > > diff --git a/kernel/rcu/rcu.h b/kernel/rcu/rcu.h > > index 115616ac3bfa..fb95de039596 100644 > > --- a/kernel/rcu/rcu.h > > +++ b/kernel/rcu/rcu.h > > @@ -14,6 +14,39 @@ > > > > /* > > * Grace-period counter management. > > + * > > + * The two lowest significant bits gather the control flags. > > + * The higher bits form the RCU sequence counter. > > + * > > + * About the control flags, a common value of 0 means that no GP is in progress. > > + * A value of 1 means that a grace period has started and is in progress. When > > + * the grace period completes, the control flags are reset to 0 and the sequence > > + * counter is incremented. > > + * > > + * However some specific RCU usages make use of custom values. > > + * > > + * SRCU special control values: > > + * > > + * SRCU_SNP_INIT_SEQ : Invalid/init value set when SRCU node > > + * is initialized. > > + * > > + * SRCU_STATE_IDLE : No SRCU gp is in progress > > + * > > + * SRCU_STATE_SCAN1 : State set by rcu_seq_start(). Indicates > > + * we are scanning the inactive readers > > + * index. > > + * > > + * SRCU_STATE_SCAN2 : State set manually via rcu_seq_set_state() > > + * Indicates we are flipping the readers > > + * index and then scanning the newly inactive > > + * readers index. > > + * > > + * RCU polled GP special control value: > > + * > > + * RCU_GET_STATE_COMPLETED : State value indicating that a polled GP > > + * has completed. It's an absolute value > > + * covering both the state and the counter of > > + * the GP sequence. > > */ > > > > #define RCU_SEQ_CTR_SHIFT 2 > > -- > > 2.34.1 > > > > Ok perhaps this one got the tabs right: > > --- > From: Frederic Weisbecker <frederic@xxxxxxxxxx> > Date: Thu, 19 Jan 2023 14:29:34 +0100 > Subject: [PATCH v2] rcu: Further comment and explain the state space of GP > sequences > > The state space of the GP sequence number isn't documented and the > definitions of its special values are scattered. Try to gather some > common knowledge near the GP seq headers. > > Signed-off-by: Frederic Weisbecker <frederic@xxxxxxxxxx> > --- > kernel/rcu/rcu.h | 33 +++++++++++++++++++++++++++++++++ > 1 file changed, 33 insertions(+) > > diff --git a/kernel/rcu/rcu.h b/kernel/rcu/rcu.h > index 115616ac3bfa..fb95de039596 100644 > --- a/kernel/rcu/rcu.h > +++ b/kernel/rcu/rcu.h > @@ -14,6 +14,39 @@ > > /* > * Grace-period counter management. > + * > + * The two lowest significant bits gather the control flags. > + * The higher bits form the RCU sequence counter. > + * > + * About the control flags, a common value of 0 means that no GP is in progress. > + * A value of 1 means that a grace period has started and is in progress. When > + * the grace period completes, the control flags are reset to 0 and the sequence > + * counter is incremented. > + * > + * However some specific RCU usages make use of custom values. > + * > + * SRCU special control values: > + * > + * SRCU_SNP_INIT_SEQ : Invalid/init value set when SRCU node > + * is initialized. > + * > + * SRCU_STATE_IDLE : No SRCU gp is in progress > + * > + * SRCU_STATE_SCAN1 : State set by rcu_seq_start(). Indicates > + * we are scanning the inactive readers > + * index. > + * > + * SRCU_STATE_SCAN2 : State set manually via rcu_seq_set_state() > + * Indicates we are flipping the readers > + * index and then scanning the newly inactive > + * readers index. > + * > + * RCU polled GP special control value: > + * > + * RCU_GET_STATE_COMPLETED : State value indicating that a polled GP > + * has completed. It's an absolute value > + * covering both the state and the counter of > + * the GP sequence. > */ Other than the minor comments in the other thread: Reviewed-by: Joel Fernandes (Google) <joel@xxxxxxxxxxxxxxxxx> thanks, - Joel > > #define RCU_SEQ_CTR_SHIFT 2 > -- > 2.34.1 >
