On Tue, Feb 25, 2025 at 10:43:45AM +0800, Oliver Sang wrote: > hi, Paul, hi, Boqun Feng, > > On Sun, Feb 23, 2025 at 08:58:16PM -0800, Paul E. McKenney wrote: > > On Sun, Feb 23, 2025 at 08:43:09PM -0800, Boqun Feng wrote: > > > From: "Paul E. McKenney" <[email protected]> > > > > > > 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 <[email protected]> > > > Closes: https://lore.kernel.org/oe-lkp/[email protected] > > > Co-developed-by: Boqun Feng <[email protected]> > > > Signed-off-by: Boqun Feng <[email protected]> > > > Co-developed-by: Joel Fernandes <[email protected]> > > > Signed-off-by: Joel Fernandes <[email protected]> > > > Signed-off-by: Paul E. McKenney <[email protected]> > > > Signed-off-by: Boqun Feng <[email protected]> > > > --- > > > 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... :-/ > > > we tested this new patch-set, and confirmed the WARN we reported is fixed by > whole patch-set. thanks > > Tested-by: kernel test robot <[email protected]> >
Thanks! > > just want to confirm one thing, we applied the patch-set as below: > > * b9aa59295f037 rcutorture: Update ->extendables check for lazy preemption > * 5ffd825e807bd rcutorture: Update rcutorture_one_extend_check() for lazy > preemption > * c9b55f9da0d2c rcu: limit PREEMPT_RCU configurations > > we also made the test upon 5ffd825e807bd, which still shows the similar WARN. > is this expected? > Yes, that's expected, and that's why commit b9aa59295f037 is needed, thank you for the double confirmation. Regards, Boqun > > > > 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) > > >
