srcu: Make Tiny SRCU use multi-bit grace-period counter

There is a need for a polling interface for SRCU grace periods.  This
polling needs to distinguish between an SRCU instance being idle on the
one hand or in the middle of a grace period on the other.  This commit
therefore converts the Tiny SRCU srcu_struct structure's srcu_idx from
a defacto boolean to a free-running counter, using the bottom bit to
indicate that a grace period is in progress.  The second-from-bottom
bit is thus used as the index returned by srcu_read_lock().

Link: https://lore.kernel.org/rcu/[email protected]/
Reported-by: Kent Overstreet <[email protected]>
[ paulmck: Fix ->srcu_lock_nesting[] indexing per Neeraj Upadhyay. ]
Reviewed-by: Neeraj Upadhyay <[email protected]>
Signed-off-by: Paul E. McKenney <[email protected]>

0 files changed, 0 insertions, 0 deletions