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rcutorture: Comment invocations of tick_dep_set_task()

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The rcu_torture_reader() and rcu_torture_fwd_prog_cr() functions
run CPU-bound for extended periods of time (tens or even
hundreds of milliseconds), so they invoke tick_dep_set_task() and
tick_dep_clear_task() to ensure that the scheduling-clock tick helps
move grace periods forward.

So why doesn't rcu_torture_fwd_prog_nr() also invoke tick_dep_set_task()
and tick_dep_clear_task()?  Because the point of this function is to test
RCU's ability to (eventually) force grace periods forward even when the
tick has been disabled during long CPU-bound kernel execution.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Joel Fernandes <joelagnelf@nvidia.com>
This commit is contained in:
Paul E. McKenney 2025-02-09 05:09:26 -08:00 committed by Joel Fernandes
parent a3204f778c
commit ed0d0db095
1 changed files with 2 additions and 2 deletions
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4
kernel/rcu/rcutorture.c
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@ -2345,7 +2345,7 @@ rcu_torture_reader(void *arg)
set_user_nice(current, MAX_NICE);
if (irqreader && cur_ops->irq_capable)
timer_setup_on_stack(&t, rcu_torture_timer, 0);
tick_dep_set_task(current, TICK_DEP_BIT_RCU);
tick_dep_set_task(current, TICK_DEP_BIT_RCU); // CPU bound, so need tick.
do {
if (irqreader && cur_ops->irq_capable) {
if (!timer_pending(&t))
@ -3074,7 +3074,7 @@ static void rcu_torture_fwd_prog_cr(struct rcu_fwd *rfp)
cver = READ_ONCE(rcu_torture_current_version);
gps = cur_ops->get_gp_seq();
rfp->rcu_launder_gp_seq_start = gps;
tick_dep_set_task(current, TICK_DEP_BIT_RCU);
tick_dep_set_task(current, TICK_DEP_BIT_RCU); // CPU bound, so need tick.
while (time_before(jiffies, stopat) &&
!shutdown_time_arrived() &&
!READ_ONCE(rcu_fwd_emergency_stop) && !torture_must_stop()) {