On 12 October 2026 11:41:34 BST, Zqiang <[email protected]> wrote: >When running the tasks-rude and srcu-atomic tests, the fwd_prog_tasks >kthread is created because the default value of fwd_progress is 1. >however, the two RCU flavors not support ->call(): > >1. tasks-rude: commit b428a9de9bba ("rcutorture: Stop testing RCU Tasks > Rude asynchronous APIs") removed .call and .cb_barrier from tasks-rude, > but left the .cbflood_max = 50000. > >2. srcu-atomic: srcu_torture_init_forbidden_apis() sets ->call to NULL > for SRCU_READ_FLAVOR_ATOMIC runs, but leaves ->cbflood_max untouched. > >In both cases, the non-zero ->cbflood_max fools the check above into >creating the fwd_prog_tasks kthreads, even though those kthreads cannot >possibly carry out any forward-progress test: > >1. The rcu_torture_fwd_prog_cr() returns immediately due to cur_ops->call > is NULL: > >[ 68.022674] rcu_torture_fwd_prog_cr: No ->call(), so no >forward-progress test 0 >[ 129.462046] rcu_torture_fwd_prog_cr: No ->call(), so no >forward-progress test 0 >[ 190.902123] rcu_torture_fwd_prog_cr: No ->call(), so no >forward-progress test 0 >[ 252.343809] rcu_torture_fwd_prog_cr: No ->call(), so no >forward-progress test 0 > >2. The rcu_torture_fwd_prog_nr() is never even invoked, because its caller > requires cur_ops->stall_dur, and neither tasks-rude nor srcu-atomic > provide ->stall_dur (only rcu_ops does). > >Therefore, creating fwd_prog_tasks kthreads is pointless, this commit >removes the .cbflood_max from tasks-rude and clears ->cbflood_max in the >srcu_torture_init_forbidden_apis(). > >simple verification output: > >[ 3.062959][ T1] srcu-torture: rcu_torture_fwd_prog_init: Disabled, >unsupported by RCU flavor under test >[ 2.922323][ T1] tasks-rude-torture: rcu_torture_fwd_prog_init: >Disabled, unsupported by RCU flavor under test
Fixes tag? This LGTM anyway so: Reviewed-by: Bradley Morgan <[email protected]> > >Signed-off-by: Zqiang <[email protected]> >--- > kernel/rcu/rcutorture.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > >diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c >index 968343be4e0d..00db87256e78 100644 >--- a/kernel/rcu/rcutorture.c >+++ b/kernel/rcu/rcutorture.c >@@ -723,6 +723,7 @@ static void srcu_torture_init_forbidden_apis(void) > cur_ops->deferred_free = NULL; > cur_ops->exp_current = NULL; > cur_ops->start_gp_poll = NULL; >+ cur_ops->cbflood_max = 0; > } > > static void srcu_torture_init(void) >@@ -1250,7 +1251,6 @@ static struct rcu_torture_ops tasks_rude_ops = { > .exp_sync = synchronize_rcu_tasks_rude, > .gp_kthread_dbg = show_rcu_tasks_rude_gp_kthread, > .get_gp_data = rcu_tasks_rude_get_gp_data, >- .cbflood_max = 50000, > .irq_capable = 1, > .name = "tasks-rude" > }; > --- Thanks! "I'm not a very positive person" - Linus torvalds
