@@ -1139,7 +1139,8 @@ static void srcu_flip(struct srcu_struct *ssp)
}
/*
- * If SRCU is likely idle, return true, otherwise return false.
+ * If SRCU is likely idle, in other words, the next SRCU grace period
+ * should be expedited, return true, otherwise return false.
*
* Note that it is OK for several current from-idle requests for a new
* grace period from idle to specify expediting because they will all end
@@ -1159,7 +1160,7 @@ static void srcu_flip(struct srcu_struct *ssp)
* negligible when amortized over that time period, and the extra latency
* of a needlessly non-expedited grace period is similarly negligible.
*/
-static bool srcu_might_be_idle(struct srcu_struct *ssp)
+static bool srcu_should_expedite(struct srcu_struct *ssp)
{
unsigned long curseq;
unsigned long flags;
@@ -1469,14 +1470,15 @@ EXPORT_SYMBOL_GPL(synchronize_srcu_expedited);
* Implementation of these memory-ordering guarantees is similar to
* that of synchronize_rcu().
*
- * If SRCU is likely idle, expedite the first request. This semantic
- * was provided by Classic SRCU, and is relied upon by its users, so TREE
- * SRCU must also provide it. Note that detecting idleness is heuristic
- * and subject to both false positives and negatives.
+ * If SRCU is likely idle as determined by srcu_should_expedite(),
+ * expedite the first request. This semantic was provided by Classic SRCU,
+ * and is relied upon by its users, so TREE SRCU must also provide it.
+ * Note that detecting idleness is heuristic and subject to both false
+ * positives and negatives.
*/
void synchronize_srcu(struct srcu_struct *ssp)
{
- if (srcu_might_be_idle(ssp) || rcu_gp_is_expedited())
+ if (srcu_should_expedite(ssp) || rcu_gp_is_expedited())
synchronize_srcu_expedited(ssp);
else
__synchronize_srcu(ssp, true);
SRCU auto-expedites grace periods that follow a sufficiently long idle period, and the srcu_might_be_idle() function is used to make this decision. However, the upcoming light-weight SRCU readers will not do auto-expediting because doing so would cause the grace-period machinery to invoke synchronize_rcu_expedited() twice, with IPIs all around. However, software-engineering considerations force this determination to remain in srcu_might_be_idle(). This commit therefore changes the name of srcu_might_be_idle() to srcu_should_expedite(), thus moving from what it currently does to why it does it, this latter being more future-proof. Signed-off-by: Paul E. McKenney <paulmck@kernel.org> Cc: Alexei Starovoitov <ast@kernel.org> Cc: Andrii Nakryiko <andrii@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Kent Overstreet <kent.overstreet@linux.dev> Cc: <bpf@vger.kernel.org> --- kernel/rcu/srcutree.c | 16 +++++++++------- 1 file changed, 9 insertions(+), 7 deletions(-)