From: "Paul E. McKenney" <paulmck@xxxxxxxxxxxxx> During an actual call_rcu() flood, there would be frequent trips to userspace (in-kernel call_rcu() floods must be otherwise housebroken). Userspace execution on nohz_full CPUs implies an RCU dyntick idle/not-idle transition pair, so this commit adds emulation of that pair. Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxxxxx> --- include/linux/rcutiny.h | 1 + kernel/rcu/rcutorture.c | 11 +++++++++++ kernel/rcu/tree.c | 1 + 3 files changed, 13 insertions(+) diff --git a/include/linux/rcutiny.h b/include/linux/rcutiny.h index 9bf1dfe..37b6f0c 100644 --- a/include/linux/rcutiny.h +++ b/include/linux/rcutiny.h @@ -84,6 +84,7 @@ static inline void rcu_scheduler_starting(void) { } #endif /* #else #ifndef CONFIG_SRCU */ static inline void rcu_end_inkernel_boot(void) { } static inline bool rcu_is_watching(void) { return true; } +static inline void rcu_momentary_dyntick_idle(void) { } /* Avoid RCU read-side critical sections leaking across. */ static inline void rcu_all_qs(void) { barrier(); } diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c index 3c9feca..7dcb2b8 100644 --- a/kernel/rcu/rcutorture.c +++ b/kernel/rcu/rcutorture.c @@ -1759,6 +1759,11 @@ static unsigned long rcu_torture_fwd_prog_cbfree(void) kfree(rfcp); freed++; rcu_torture_fwd_prog_cond_resched(freed); + if (tick_nohz_full_enabled()) { + local_irq_save(flags); + rcu_momentary_dyntick_idle(); + local_irq_restore(flags); + } } return freed; } @@ -1833,6 +1838,7 @@ static void rcu_torture_fwd_prog_nr(int *tested, int *tested_tries) static void rcu_torture_fwd_prog_cr(void) { unsigned long cver; + unsigned long flags; unsigned long gps; int i; long n_launders; @@ -1891,6 +1897,11 @@ static void rcu_torture_fwd_prog_cr(void) } cur_ops->call(&rfcp->rh, rcu_torture_fwd_cb_cr); rcu_torture_fwd_prog_cond_resched(n_launders + n_max_cbs); + if (tick_nohz_full_enabled()) { + local_irq_save(flags); + rcu_momentary_dyntick_idle(); + local_irq_restore(flags); + } } stoppedat = jiffies; n_launders_cb_snap = READ_ONCE(n_launders_cb); diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index 8110514..5692db5 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -375,6 +375,7 @@ static void __maybe_unused rcu_momentary_dyntick_idle(void) WARN_ON_ONCE(!(special & RCU_DYNTICK_CTRL_CTR)); rcu_preempt_deferred_qs(current); } +EXPORT_SYMBOL_GPL(rcu_momentary_dyntick_idle); /** * rcu_is_cpu_rrupt_from_idle - see if interrupted from idle -- 2.9.5