tree 4d60ad4b077ec6f719593bd809f9bb9e7fc79bc7
parent ce9ae1556b05c29528336f77a32c0ce8716f3fad
author Paul E. McKenney <paulmck@kernel.org> 1643245386 -0800
committer Paul E. McKenney <paulmck@kernel.org> 1643245386 -0800

srcu: Use invalid initial value for srcu_node GP sequence numbers

Currently, tree SRCU relies on the srcu_node structures being initialized
at the same time that the srcu_struct itself is initialized, and thus
use the initial grace-period sequence number as the initial value for
the srcu_node structure's ->srcu_have_cbs[] and ->srcu_gp_seq_needed_exp
fields.  Although this has a high probability of also working when the
srcu_node array is allocated and initialized at some random later time,
it would be better to avoid leaving such things to chance.

This commit therefore initializes these fields with 0x1, which is a
recognizable invalid value.  It then adds the required checks for this
invalid value in order to avoid confusion on long-running kernels
(especially those on 32-bit systems) that allocate and initialize
srcu_node arrays late in life.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>