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/20250217/202502171415.8ec87c87-lkp@xxxxxxxxx/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/20250217/202502171415.8ec87c87-lkp@xxxxxxxxx
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))
+ 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 <paulmck@xxxxxxxxxx>
> > > 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 <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>
> > >
> > > 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);
> > > }
> > >
> > >
>
>
Attachment:
dmesg.xz
Description: application/xz
