Commit bd1bfc51 authored by Paul E. McKenney's avatar Paul E. McKenney
Browse files

rcutorture: Emulate userspace sojourn during call_rcu() floods 



During an actual call_rcu() flood, there would be frequent trips to
userspace (in-kernel call_rcu() floods must be otherwise housebroken).
Userspace execution allows a great many things to interrupt execution,
and rcutorture needs to also allow such interruptions.  This commit
therefore causes call_rcu() floods to occasionally invoke schedule(),
thus preventing spurious rcutorture failures due to other parts of the
kernel becoming irate at the call_rcu() flood events.

Signed-off-by: default avatarPaul E. McKenney <paulmck@linux.ibm.com>
parent f4e83529

kernel/rcu/rcutorture.c

+7 −5
Original line number Diff line number Diff line
@@ -1713,12 +1713,14 @@ static void rcu_torture_fwd_cb_cr(struct rcu_head *rhp) 
}



// Give the scheduler a chance, even on nohz_full CPUs.

static void rcu_torture_fwd_prog_cond_resched(void)

static void rcu_torture_fwd_prog_cond_resched(unsigned long iter)

{

	if (IS_ENABLED(CONFIG_PREEMPT) && IS_ENABLED(CONFIG_NO_HZ_FULL)) {

		if (need_resched())

		// Real call_rcu() floods hit userspace, so emulate that.

		if (need_resched() || (iter & 0xfff))

			schedule();

	} else {

		// No userspace emulation: CB invocation throttles call_rcu()

		cond_resched();

	}

}
@@ -1746,7 +1748,7 @@ static unsigned long rcu_torture_fwd_prog_cbfree(void) 
		spin_unlock_irqrestore(&rcu_fwd_lock, flags);

		kfree(rfcp);

		freed++;

		rcu_torture_fwd_prog_cond_resched();

		rcu_torture_fwd_prog_cond_resched(freed);

	}

	return freed;

}
@@ -1790,7 +1792,7 @@ static void rcu_torture_fwd_prog_nr(int *tested, int *tested_tries) 
		udelay(10);

		cur_ops->readunlock(idx);

		if (!fwd_progress_need_resched || need_resched())

			rcu_torture_fwd_prog_cond_resched();

			rcu_torture_fwd_prog_cond_resched(1);

	}

	(*tested_tries)++;

	if (!time_before(jiffies, stopat) &&
@@ -1875,7 +1877,7 @@ static void rcu_torture_fwd_prog_cr(void) 
			rfcp->rfc_gps = 0;

		}

		cur_ops->call(&rfcp->rh, rcu_torture_fwd_cb_cr);

		rcu_torture_fwd_prog_cond_resched();

		rcu_torture_fwd_prog_cond_resched(n_launders + n_max_cbs);

	}

	stoppedat = jiffies;

	n_launders_cb_snap = READ_ONCE(n_launders_cb);