Commit 1c3d5398 authored by Paul E. McKenney's avatar Paul E. McKenney
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rcutorture: More thoroughly test nested readers 



Currently, nested readers occur only when a timer handler interrupts a
reader.  This is rare, and is thus insufficient testing of the transition
between nesting levels.  This commit therefore causes rcutorture nested
readers to be the rule rather than the exception.

Signed-off-by: default avatarPaul E. McKenney <paulmck@kernel.org>
parent 902d82e6

kernel/rcu/rcutorture.c

+50 −23
Original line number Diff line number Diff line
@@ -53,15 +53,18 @@ MODULE_LICENSE("GPL"); 
MODULE_AUTHOR("Paul E. McKenney <paulmck@linux.ibm.com> and Josh Triplett <josh@joshtriplett.org>");



/* Bits for ->extendables field, extendables param, and related definitions. */

#define RCUTORTURE_RDR_SHIFT	 8	/* Put SRCU index in upper bits. */

#define RCUTORTURE_RDR_MASK	 (1 << RCUTORTURE_RDR_SHIFT)

#define RCUTORTURE_RDR_SHIFT_1	 8	/* Put SRCU index in upper bits. */

#define RCUTORTURE_RDR_MASK_1	 (1 << RCUTORTURE_RDR_SHIFT_1)

#define RCUTORTURE_RDR_SHIFT_2	 9	/* Put SRCU index in upper bits. */

#define RCUTORTURE_RDR_MASK_2	 (1 << RCUTORTURE_RDR_SHIFT_2)

#define RCUTORTURE_RDR_BH	 0x01	/* Extend readers by disabling bh. */

#define RCUTORTURE_RDR_IRQ	 0x02	/*  ... disabling interrupts. */

#define RCUTORTURE_RDR_PREEMPT	 0x04	/*  ... disabling preemption. */

#define RCUTORTURE_RDR_RBH	 0x08	/*  ... rcu_read_lock_bh(). */

#define RCUTORTURE_RDR_SCHED	 0x10	/*  ... rcu_read_lock_sched(). */

#define RCUTORTURE_RDR_RCU	 0x20	/*  ... entering another RCU reader. */

#define RCUTORTURE_RDR_NBITS	 6	/* Number of bits defined above. */

#define RCUTORTURE_RDR_RCU_1	 0x20	/*  ... entering another RCU reader. */

#define RCUTORTURE_RDR_RCU_2	 0x40	/*  ... entering another RCU reader. */

#define RCUTORTURE_RDR_NBITS	 7	/* Number of bits defined above. */

#define RCUTORTURE_MAX_EXTEND	 \

	(RCUTORTURE_RDR_BH | RCUTORTURE_RDR_IRQ | RCUTORTURE_RDR_PREEMPT | \

	 RCUTORTURE_RDR_RBH | RCUTORTURE_RDR_SCHED)
@@ -1420,13 +1423,15 @@ static void rcutorture_one_extend(int *readstate, int newstate, 
				  struct rt_read_seg *rtrsp)

{

	unsigned long flags;

	int idxnew = -1;

	int idxold = *readstate;

	int idxnew1 = -1;

	int idxnew2 = -1;

	int idxold1 = *readstate;

	int idxold2 = idxold1;

	int statesnew = ~*readstate & newstate;

	int statesold = *readstate & ~newstate;



	WARN_ON_ONCE(idxold < 0);

	WARN_ON_ONCE((idxold >> RCUTORTURE_RDR_SHIFT) > 1);

	WARN_ON_ONCE(idxold2 < 0);

	WARN_ON_ONCE((idxold2 >> RCUTORTURE_RDR_SHIFT_2) > 1);

	rtrsp->rt_readstate = newstate;



	/* First, put new protection in place to avoid critical-section gap. */
@@ -1440,8 +1445,10 @@ static void rcutorture_one_extend(int *readstate, int newstate, 
		preempt_disable();

	if (statesnew & RCUTORTURE_RDR_SCHED)

		rcu_read_lock_sched();

	if (statesnew & RCUTORTURE_RDR_RCU)

		idxnew = cur_ops->readlock() << RCUTORTURE_RDR_SHIFT;

	if (statesnew & RCUTORTURE_RDR_RCU_1)

		idxnew1 = (cur_ops->readlock() & 0x1) << RCUTORTURE_RDR_SHIFT_1;

	if (statesnew & RCUTORTURE_RDR_RCU_2)

		idxnew2 = (cur_ops->readlock() & 0x1) << RCUTORTURE_RDR_SHIFT_2;



	/*

	 * Next, remove old protection, in decreasing order of strength
@@ -1460,13 +1467,19 @@ static void rcutorture_one_extend(int *readstate, int newstate, 
		local_bh_enable();

	if (statesold & RCUTORTURE_RDR_RBH)

		rcu_read_unlock_bh();

	if (statesold & RCUTORTURE_RDR_RCU) {

	if (statesold & RCUTORTURE_RDR_RCU_2) {

		cur_ops->readunlock((idxold2 >> RCUTORTURE_RDR_SHIFT_2) & 0x1);

		WARN_ON_ONCE(idxnew2 != -1);

		idxold2 = 0;

	}

	if (statesold & RCUTORTURE_RDR_RCU_1) {

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



		if (lockit)

			raw_spin_lock_irqsave(&current->pi_lock, flags);

		cur_ops->readunlock(idxold >> RCUTORTURE_RDR_SHIFT);

		idxold = 0;

		cur_ops->readunlock((idxold1 >> RCUTORTURE_RDR_SHIFT_1) & 0x1);

		WARN_ON_ONCE(idxnew1 != -1);

		idxold1 = 0;

		if (lockit)

			raw_spin_unlock_irqrestore(&current->pi_lock, flags);

	}
@@ -1476,13 +1489,19 @@ static void rcutorture_one_extend(int *readstate, int newstate, 
		cur_ops->read_delay(trsp, rtrsp);



	/* Update the reader state. */

	if (idxnew == -1)

		idxnew = idxold & RCUTORTURE_RDR_MASK;

	WARN_ON_ONCE(idxnew < 0);

	WARN_ON_ONCE((idxnew >> RCUTORTURE_RDR_SHIFT) > 1);

	*readstate = idxnew | newstate;

	WARN_ON_ONCE((*readstate >> RCUTORTURE_RDR_SHIFT) < 0);

	WARN_ON_ONCE((*readstate >> RCUTORTURE_RDR_SHIFT) > 1);

	if (idxnew1 == -1)

		idxnew1 = idxold1 & RCUTORTURE_RDR_MASK_1;

	WARN_ON_ONCE(idxnew1 < 0);

	if (WARN_ON_ONCE((idxnew1 >> RCUTORTURE_RDR_SHIFT_1) > 1))

		pr_info("Unexpected idxnew1 value of %#x\n", idxnew1);

	if (idxnew2 == -1)

		idxnew2 = idxold2 & RCUTORTURE_RDR_MASK_2;

	WARN_ON_ONCE(idxnew2 < 0);

	WARN_ON_ONCE((idxnew2 >> RCUTORTURE_RDR_SHIFT_2) > 1);

	*readstate = idxnew1 | idxnew2 | newstate;

	WARN_ON_ONCE(*readstate < 0);

	if (WARN_ON_ONCE((*readstate >> RCUTORTURE_RDR_SHIFT_2) > 1))

		pr_info("Unexpected idxnew2 value of %#x\n", idxnew2);

}



/* Return the biggest extendables mask given current RCU and boot parameters. */
@@ -1492,7 +1511,7 @@ static int rcutorture_extend_mask_max(void) 


	WARN_ON_ONCE(extendables & ~RCUTORTURE_MAX_EXTEND);

	mask = extendables & RCUTORTURE_MAX_EXTEND & cur_ops->extendables;

	mask = mask | RCUTORTURE_RDR_RCU;

	mask = mask | RCUTORTURE_RDR_RCU_1 | RCUTORTURE_RDR_RCU_2;

	return mask;

}
@@ -1507,13 +1526,21 @@ rcutorture_extend_mask(int oldmask, struct torture_random_state *trsp) 
	unsigned long preempts_irq = preempts | RCUTORTURE_RDR_IRQ;

	unsigned long bhs = RCUTORTURE_RDR_BH | RCUTORTURE_RDR_RBH;



	WARN_ON_ONCE(mask >> RCUTORTURE_RDR_SHIFT);

	WARN_ON_ONCE(mask >> RCUTORTURE_RDR_SHIFT_1);

	/* Mostly only one bit (need preemption!), sometimes lots of bits. */

	if (!(randmask1 & 0x7))

		mask = mask & randmask2;

	else

		mask = mask & (1 << (randmask2 % RCUTORTURE_RDR_NBITS));



	// Can't have nested RCU reader without outer RCU reader.

	if (!(mask & RCUTORTURE_RDR_RCU_1) && (mask & RCUTORTURE_RDR_RCU_2)) {

		if (oldmask & RCUTORTURE_RDR_RCU_1)

			mask &= ~RCUTORTURE_RDR_RCU_2;

		else

			mask |= RCUTORTURE_RDR_RCU_1;

	}



	/*

	 * Can't enable bh w/irq disabled.

	 */
@@ -1533,7 +1560,7 @@ rcutorture_extend_mask(int oldmask, struct torture_random_state *trsp) 
			mask |= oldmask & bhs;

	}



	return mask ?: RCUTORTURE_RDR_RCU;

	return mask ?: RCUTORTURE_RDR_RCU_1;

}



/*