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rcutorture: Make rcu_fwd_cb_nodelay be a counter

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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@kernel.org>
This commit is contained in:
Paul E. McKenney 2021-12-17 12:33:53 -08:00
parent 05b724655b
commit e22ef8df41
1 changed files with 7 additions and 7 deletions
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14
kernel/rcu/rcutorture.c
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@ -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);
}