On Sun, Feb 23, 2025 at 08:43:09PM -0800, Boqun Feng wrote: > From: "Paul E. McKenney" <paulmck@xxxxxxxxxx> > > 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: kernel test robot <oliver.sang@xxxxxxxxx> > Closes: https://lore.kernel.org/oe-lkp/202502171415.8ec87c87-lkp@xxxxxxxxx > Co-developed-by: Boqun Feng <boqun.feng@xxxxxxxxx> > Signed-off-by: Boqun Feng <boqun.feng@xxxxxxxxx> > Co-developed-by: Joel Fernandes <joelagnelf@xxxxxxxxxx> > Signed-off-by: Joel Fernandes <joelagnelf@xxxxxxxxxx> > Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxx> > Signed-off-by: Boqun Feng <boqun.feng@xxxxxxxxx> > --- > kernel/rcu/rcutorture.c | 14 ++++++++++++-- > 1 file changed, 12 insertions(+), 2 deletions(-) > > diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c > index d26fb1d33ed9..280bff706017 100644 > --- a/kernel/rcu/rcutorture.c > +++ b/kernel/rcu/rcutorture.c > @@ -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)) Good catch, thank you, and it looks good to me! Oliver, you are right, I was looking at the wrong console output. One of those days, I guess... :-/ Thanx, Paul > + mask |= RCUTORTURE_RDR_PREEMPT | RCUTORTURE_RDR_SCHED; > + > + WARN_ONCE(cur_ops->readlock_nesting && !(curstate & mask) && > cur_ops->readlock_nesting() > 0, ROEC_ARGS); > } > > -- > 2.39.5 (Apple Git-154) >
