[PATCH tip/core/rcu 24/28] rcutorture: Don't do need_resched() testing if ->sync is NULL

paulmck
2020-11-05T23:47:57Z

If cur_ops->sync is NULL, rcu_torture_fwd_prog_nr() will nevertheless
attempt to call through it. This commit therefore flags cases where
neither need_resched() nor call_rcu() forward-progress testing
can be performed due to NULL function pointers, and also causes
rcu_torture_fwd_prog_nr() to take an early exit if cur_ops->sync()
is NULL.

Reported-by: Tom Rix <trix@redhat.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
kernel/rcu/rcutorture.c | 8 +++++---
1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
index e7d52fd..f4c0655 100644
--- a/kernel/rcu/rcutorture.c
+++ b/kernel/rcu/rcutorture.c
@@ -1923,7 +1923,9 @@ static void rcu_torture_fwd_prog_nr(struct rcu_fwd *rfp,
unsigned long stopat;
static DEFINE_TORTURE_RANDOM(trs);

- if (cur_ops->call && cur_ops->sync && cur_ops->cb_barrier) {
+ if (!cur_ops->sync)
+ return; // Cannot do need_resched() forward progress testing without ->sync.
+ if (cur_ops->call && cur_ops->cb_barrier) {
init_rcu_head_on_stack(&fcs.rh);
selfpropcb = true;
}
@@ -2149,8 +2151,8 @@ static int __init rcu_torture_fwd_prog_init(void)

if (!fwd_progress)
return 0; /* Not requested, so don't do it. */
- if (!cur_ops->stall_dur || cur_ops->stall_dur() <= 0 ||
- cur_ops == &rcu_busted_ops) {
+ if ((!cur_ops->sync && !cur_ops->call) ||
+ !cur_ops->stall_dur || cur_ops->stall_dur() <= 0 || cur_ops == &rcu_busted_ops) {
VERBOSE_TOROUT_STRING("rcu_torture_fwd_prog_init: Disabled, unsupported by RCU flavor under test");
return 0;
}
--
2.9.5