Commit 52b1fc3f authored by Paul E. McKenney's avatar Paul E. McKenney
Browse files

rcutorture: Add test of holding scheduler locks across rcu_read_unlock() 



Now that it should be safe to hold scheduler locks across
rcu_read_unlock(), even in cases where the corresponding RCU read-side
critical section might have been preempted and boosted, the commit adds
a test of this capability to rcutorture.  This has been tested on current
mainline (which can deadlock in this situation), and lockdep duly reported
the expected deadlock.  On -rcu, lockdep is silent, thus far, anyway.

Cc: Ingo Molnar <mingo@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: Vincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: default avatarPaul E. McKenney <paulmck@kernel.org>
parent 5f5fa7ea

kernel/rcu/rcutorture.c

+9 −1
Original line number Diff line number Diff line
@@ -1147,6 +1147,7 @@ static void rcutorture_one_extend(int *readstate, int newstate, 
				  struct torture_random_state *trsp,

				  struct rt_read_seg *rtrsp)

{

	unsigned long flags;

	int idxnew = -1;

	int idxold = *readstate;

	int statesnew = ~*readstate & newstate;
@@ -1181,8 +1182,15 @@ static void rcutorture_one_extend(int *readstate, int newstate, 
		rcu_read_unlock_bh();

	if (statesold & RCUTORTURE_RDR_SCHED)

		rcu_read_unlock_sched();

	if (statesold & RCUTORTURE_RDR_RCU)

	if (statesold & RCUTORTURE_RDR_RCU) {

		bool lockit = !statesnew && !(torture_random(trsp) & 0xffff);



		if (lockit)

			raw_spin_lock_irqsave(&current->pi_lock, flags);

		cur_ops->readunlock(idxold >> RCUTORTURE_RDR_SHIFT);

		if (lockit)

			raw_spin_unlock_irqrestore(&current->pi_lock, flags);

	}



	/* Delay if neither beginning nor end and there was a change. */

	if ((statesnew || statesold) && *readstate && newstate)