srcu: Begin offloading srcu_struct fields to srcu_update

The current srcu_struct structure is on the order of 200 bytes in size
(depending on architecture and .config), which is much better than the
old-style 26K bytes, but still all too inconvenient when one is trying
to achieve good cache locality on a fastpath involving SRCU readers.

However, only a few fields in srcu_struct are used by SRCU readers.
The remaining fields could be offloaded to a new srcu_update
structure, thus shrinking the srcu_struct structure down to a few
tens of bytes.  This commit begins this noble quest, a quest that is
complicated by open-coded initialization of the srcu_struct within the
srcu_notifier_head structure.  This complication is addressed by updating
the srcu_notifier_head structure's open coding, given that there does
not appear to be a straightforward way of abstracting that initialization.

This commit moves only the ->node pointer to srcu_update.  Later commits
will move additional fields.

[ paulmck: Fold in [email protected]'s memory-leak fix. ]

Link: https://lore.kernel.org/all/[email protected]/
Suggested-by: Christoph Hellwig <[email protected]>
Cc: "Rafael J. Wysocki" <[email protected]>
Cc: "Michał Mirosław" <[email protected]>
Cc: Dmitry Osipenko <[email protected]>
Tested-by: Sachin Sant <[email protected]>
Tested-by: "Zhang, Qiang1" <[email protected]>
Acked-by: Rafael J. Wysocki <[email protected]>
Tested-by: Joel Fernandes (Google) <[email protected]>
Signed-off-by: Paul E. McKenney <[email protected]>

0 files changed, 0 insertions, 0 deletions