I finally find why I cannot reproduce this, I accidentally used
next.2025.02.10a to build the kernel first, which has commit
("rcutorture: Move RCU_TORTURE_TEST_{CHK_RDR_STATE,LOG_CPU} to bool"),
which changes Kconfig RCU_TORTURE_TEST_CHK_DRD_STATE into a bool and
that disabled the test... (because config from you has it as =m).
On Mon, Feb 24, 2025 at 10:22:02AM +0800, Oliver Sang wrote:
> hi, Paul,
>
> On Fri, Feb 21, 2025 at 05:02:51PM -0800, Paul E. McKenney wrote:
>
> [...]
>
> > > >
> > > > And rcutorture's WARN_ON() has a bug that is exposed by that change
> > > > in Kconfig option. Does the patch shown below help?
> > >
> > > the patch does not fix the WARNING in our tests. attached one dmesg FYI.
> >
> > Just to make sure that I understand, this patch was applied against this
> > commit, correct?
> >
> > c9b55f9da0d2 ("rcu: limit PREEMPT_RCU configurations")
> >
> > I am guessing this based on this dmesg line:
> >
> > [ 109.553307][ T781] CPU: 1 UID: 0 PID: 781 Comm: rcu_torture_rea
> > Tainted: G T 6.14.0-rc1-00007-gc9b55f9da0d2 #1
>
> above line is not from the dmesg I attached in last mail. it's from
> https://download.01.org/0day-ci/archive/20250217/[email protected]/dmesg.xz
> which is for our original report.
>
> >
> > Is this really the case, or am I confused?
>
> we applied your patch as:
>
> 89519085afdf2 fix for c9b55f9da0 from Paul
> c9b55f9da0d2c rcu: limit PREEMPT_RCU configurations
> f001b7165def8 osnoise: provide quiescent states
>
> so in the dmesg I attached in last mail (I attached it again in this mail):
>
> [ 0.000000][ T0] Linux version 6.14.0-rc1-00008-g89519085afdf
> (kbuild@9871be4fdbcc) (gcc-12 (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils
> for Debian) 2.40) #1 SMP PREEMPT Fri Feb 21 00:34:02 CST 2025
> ...
> [ 117.463907][ T812] CPU: 1 UID: 0 PID: 812 Comm: rcu_torture_rea Tainted:
> G T 6.14.0-rc1-00008-g89519085afdf #1
>
> the change of this 89519085afdf2 is as [1]
>
> I'm not sure if it's better to upload dmesg for fix patch to
> https://download.01.org/0day-ci/archive/20250217/[email protected]
> again, so I did not do that. sorry if this causes confusion.
>
> not sure if this is the correct applyment? thanks
>
> [1]
> diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
> index d26fb1d33ed9a..de85a88810cf6 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 +1904,10 @@ 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))
> &&
> + mask = RCUTORTURE_RDR_RCU_1 | RCUTORTURE_RDR_RCU_2;
> + if (IS_ENABLED(CONFIG_PREEMPT_RCU))
Now look into this, I think this should be:
if (!IS_ENABLED(CONFIG_PREEMPT_RCU))
because:
* For preemptible RCU, ->readlock_nesting() will return
rcu_preempt_depth()
* For non-preemptible RCU, ->readlock_nesting() will return
preempt count.
, which means if RCUTORTURE_RDR_PREEMPT or RCUTORTURE_RDR_SCHED is in
the curstate for *non-preemption RCU*, ->readlock_nesting() will be >0.
That is, the "mask" needs to consider _PREEMPT and _SCHED for
*non-preemption RCU*, not preemptible RCU.
Paul? Did I get it right?
Regards,
Boqun
> + mask |= RCUTORTURE_RDR_PREEMPT | RCUTORTURE_RDR_SCHED;
> + WARN_ONCE(cur_ops->readlock_nesting && !(curstate & mask) &&
> cur_ops->readlock_nesting() > 0, ROEC_ARGS);
> }
>
>
>
> >
> > Thanx, Paul
> >
> > > > Either way, thank you for your testing efforts!
> > > >
> > > > Thanx, Paul
> > > >
> > > > ------------------------------------------------------------------------
> > > >
> > > > commit bb638fe1a683316397d5517cb7d1797d70d21c86
> > > > Author: Paul E. McKenney <[email protected]>
> > > > Date: Wed Feb 19 08:41:11 2025 -0800
> > > >
> > > > 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.
> > > >
> > > > 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]>
> > > >
> > > > diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
> > > > index 895a27545ae1e..0f446ff04eda1 100644
> > > > --- a/kernel/rcu/rcutorture.c
> > > > +++ b/kernel/rcu/rcutorture.c
> > > > @@ -1981,6 +1981,8 @@ 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;
> > > >
> > > > @@ -2010,8 +2012,10 @@ 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)) &&
> > > > + 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);
> > > > }
> > > >
> > > >
> >
> >
