Commit 79ba7ff5 authored by Paul E. McKenney's avatar Paul E. McKenney
Browse files

rcutorture: Emulate dyntick aspect of userspace nohz_full sojourn 



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: default avatarPaul E. McKenney <paulmck@kernel.org>
parent 96926686

include/linux/rcutiny.h

+1 −0
Original line number Diff line number Diff line
@@ -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(); }

kernel/rcu/rcutorture.c

+11 −0
Original line number Diff line number Diff line
@@ -1761,6 +1761,11 @@ 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;

}
@@ -1835,6 +1840,7 @@ 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;
@@ -1894,6 +1900,11 @@ 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);

kernel/rcu/tree.c

+1 −0
Original line number Diff line number Diff line
@@ -375,6 +375,7 @@ void 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

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