Commit 0be4b19e authored by Paul E. McKenney's avatar Paul E. McKenney Committed by Boqun Feng
Browse files

rcutorture: Update rcutorture_one_extend_check() for lazy preemption 



The rcutorture_one_extend_check() function's last check assumes that
if cur_ops->readlock_nesting() returns greater than zero, either the
RCUTORTURE_RDR_RCU_1 or the RCUTORTURE_RDR_RCU_2 bit must be set, that
is, there must be at least one rcu_read_lock() in effect.

This works for preemptible RCU and for non-preemptible RCU running in
a non-preemptible kernel.  But it fails for non-preemptible RCU running
in a preemptible kernel because then RCU's cur_ops->readlock_nesting()
function, which is rcu_torture_readlock_nesting(), will return
the PREEMPT_MASK mask bits from preempt_count().  The result will
be greater than zero if preemption is disabled, including by the
RCUTORTURE_RDR_PREEMPT and RCUTORTURE_RDR_SCHED bits.

This commit therefore adjusts this check to take into account the case
fo non-preemptible RCU running in a preemptible kernel.

[boqun: Fix the if condition and add comment]

Reported-by: default avatarkernel test robot <oliver.sang@intel.com>
Closes: https://lore.kernel.org/oe-lkp/202502171415.8ec87c87-lkp@intel.com


Co-developed-by: default avatarBoqun Feng <boqun.feng@gmail.com>
Signed-off-by: default avatarBoqun Feng <boqun.feng@gmail.com>
Co-developed-by: default avatarJoel Fernandes <joelagnelf@nvidia.com>
Signed-off-by: default avatarJoel Fernandes <joelagnelf@nvidia.com>
Signed-off-by: default avatarPaul E. McKenney <paulmck@kernel.org>
Tested-by: default avatarkernel test robot <oliver.sang@intel.com>
Signed-off-by: default avatarBoqun Feng <boqun.feng@gmail.com>
parent 9fd858cc

kernel/rcu/rcutorture.c

+12 −2
Original line number Diff line number Diff line
@@ -1873,6 +1873,8 @@ static void rcu_torture_reader_do_mbchk(long myid, struct rcu_torture *rtp, 
#define ROEC_ARGS "%s %s: Current %#x  To add %#x  To remove %#x  preempt_count() %#x\n", __func__, s, curstate, new, old, preempt_count()

static void rcutorture_one_extend_check(char *s, int curstate, int new, int old, bool insoftirq)

{

	int mask;



	if (!IS_ENABLED(CONFIG_RCU_TORTURE_TEST_CHK_RDR_STATE))

		return;
@@ -1902,8 +1904,16 @@ static void rcutorture_one_extend_check(char *s, int curstate, int new, int old, 
	WARN_ONCE(cur_ops->extendables &&

		  !(curstate & (RCUTORTURE_RDR_PREEMPT | RCUTORTURE_RDR_SCHED)) &&

		  (preempt_count() & PREEMPT_MASK), ROEC_ARGS);

	WARN_ONCE(cur_ops->readlock_nesting &&

		  !(curstate & (RCUTORTURE_RDR_RCU_1 | RCUTORTURE_RDR_RCU_2)) &&



	/*

	 * non-preemptible RCU in a preemptible kernel uses "preempt_count() &

	 * PREEMPT_MASK" as ->readlock_nesting().

	 */

	mask = RCUTORTURE_RDR_RCU_1 | RCUTORTURE_RDR_RCU_2;

	if (!IS_ENABLED(CONFIG_PREEMPT_RCU))

		mask |= RCUTORTURE_RDR_PREEMPT | RCUTORTURE_RDR_SCHED;



	WARN_ONCE(cur_ops->readlock_nesting && !(curstate & mask) &&

		  cur_ops->readlock_nesting() > 0, ROEC_ARGS);

}