Back when only one rcutorture kthread could do forward-progress testing,
it was just fine for rcu_fwd_cb_nodelay to be a non-atomic bool. It was
set at the start of forward-progress testing and cleared at the end.
But now that there are multiple threads, the value can be cleared while
one of the threads is still doing forward-progress testing. This commit
therefore makes rcu_fwd_cb_nodelay be an atomic counter, replacing the
WRITE_ONCE() operations with atomic_inc() and atomic_dec().
Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxx>
---
kernel/rcu/rcutorture.c | 14 +++++++-------
1 file changed, 7 insertions(+), 7 deletions(-)
diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
index fefc3fa1a9c2a..afe95c6948957 100644
--- a/kernel/rcu/rcutorture.c
+++ b/kernel/rcu/rcutorture.c
@@ -284,7 +284,7 @@ static atomic_t barrier_cbs_invoked; /* Barrier callbacks invoked. */
static wait_queue_head_t *barrier_cbs_wq; /* Coordinate barrier testing. */
static DECLARE_WAIT_QUEUE_HEAD(barrier_wq);
-static bool rcu_fwd_cb_nodelay; /* Short rcu_torture_delay() delays. */
+static atomic_t rcu_fwd_cb_nodelay; /* Short rcu_torture_delay() delays. */
/*
* Allocate an element from the rcu_tortures pool.
@@ -387,7 +387,7 @@ rcu_read_delay(struct torture_random_state *rrsp, struct rt_read_seg *rtrsp)
* period, and we want a long delay occasionally to trigger
* force_quiescent_state. */
- if (!READ_ONCE(rcu_fwd_cb_nodelay) &&
+ if (!atomic_read(&rcu_fwd_cb_nodelay) &&
!(torture_random(rrsp) % (nrealreaders * 2000 * longdelay_ms))) {
started = cur_ops->get_gp_seq();
ts = rcu_trace_clock_local();
@@ -1276,7 +1276,7 @@ rcu_torture_writer(void *arg)
boot_ended = rcu_inkernel_boot_has_ended();
stutter_waited = stutter_wait("rcu_torture_writer");
if (stutter_waited &&
- !READ_ONCE(rcu_fwd_cb_nodelay) &&
+ !atomic_read(&rcu_fwd_cb_nodelay) &&
!cur_ops->slow_gps &&
!torture_must_stop() &&
boot_ended)
@@ -2290,7 +2290,7 @@ static void rcu_torture_fwd_prog_nr(struct rcu_fwd *rfp,
}
/* Tight loop containing cond_resched(). */
- WRITE_ONCE(rcu_fwd_cb_nodelay, true);
+ atomic_inc(&rcu_fwd_cb_nodelay);
cur_ops->sync(); /* Later readers see above write. */
if (selfpropcb) {
WRITE_ONCE(fcs.stop, 0);
@@ -2335,7 +2335,7 @@ static void rcu_torture_fwd_prog_nr(struct rcu_fwd *rfp,
destroy_rcu_head_on_stack(&fcs.rh);
}
schedule_timeout_uninterruptible(HZ / 10); /* Let kthreads recover. */
- WRITE_ONCE(rcu_fwd_cb_nodelay, false);
+ atomic_dec(&rcu_fwd_cb_nodelay);
}
/* Carry out call_rcu() forward-progress testing. */
@@ -2362,7 +2362,7 @@ static void rcu_torture_fwd_prog_cr(struct rcu_fwd *rfp)
return; /* Can't do call_rcu() fwd prog without ->call. */
/* Loop continuously posting RCU callbacks. */
- WRITE_ONCE(rcu_fwd_cb_nodelay, true);
+ atomic_inc(&rcu_fwd_cb_nodelay);
cur_ops->sync(); /* Later readers see above write. */
WRITE_ONCE(rfp->rcu_fwd_startat, jiffies);
stopat = rfp->rcu_fwd_startat + MAX_FWD_CB_JIFFIES;
@@ -2435,7 +2435,7 @@ static void rcu_torture_fwd_prog_cr(struct rcu_fwd *rfp)
}
schedule_timeout_uninterruptible(HZ); /* Let CBs drain. */
tick_dep_clear_task(current, TICK_DEP_BIT_RCU);
- WRITE_ONCE(rcu_fwd_cb_nodelay, false);
+ atomic_dec(&rcu_fwd_cb_nodelay);
}
--
2.31.1.189.g2e36527f23
