srcu: Fix the comparision in srcu_invl_snp_seq()

A grace-period sequence number contains two fields: counter and
state.  SRCU_SNP_INIT_SEQ provides a guaranteed invalid value for
grace-period sequence numbers in newly allocated srcu_node structures'
->srcu_have_cbs[] and ->srcu_gp_seq_needed_exp fields.  The point of the
comparison in srcu_invl_snp_seq() is not to detect invalid grace-period
sequence numbers in general, but rather to detect a newly allocated
srcu_node structure whose ->srcu_have_cbs[] and ->srcu_gp_seq_needed_exp
fields need to be brought into line with the srcu_struct structure's
->srcu_gp_seq field.

This commit therefore causes srcu_invl_snp_seq() to compare both fields
of the specified grace-period sequence number.

Signed-off-by: Pingfan Liu <kernelfans@gmail.com>
Cc: Lai Jiangshan <jiangshanlai@gmail.com>
Cc: "Paul E. McKenney" <paulmck@kernel.org>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: <rcu@vger.kernel.org>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c
index 16953784a0bdfa83e00e1d62980a09466b7b4047..6af0312005801c46cbcf9b12bdcf8288c0963a19 100644 (file)
--- a/kernel/rcu/srcutree.c
+++ b/kernel/rcu/srcutree.c
@@ -154,7 +154,7 @@ static void init_srcu_struct_data(struct srcu_struct *ssp)
  */
 static inline bool srcu_invl_snp_seq(unsigned long s)
 {
-       return rcu_seq_state(s) == SRCU_SNP_INIT_SEQ;
+       return s == SRCU_SNP_INIT_SEQ;
 }
 
 /*