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McKenney" , Ankur Arora , oe-lkp@lists.linux.dev, lkp@intel.com, Peter Zijlstra , Frederic Weisbecker , rcu@vger.kernel.org Subject: Re: [linux-next:master] [rcu] c9b55f9da0: WARNING:at_kernel/rcu/rcutorture.c:#rcutorture_one_extend_check[rcutorture] Message-ID: References: <202502171415.8ec87c87-lkp@intel.com> <08e755d1-9f7d-4238-ac2d-1869d68a8ddc@paulmck-laptop> <64d58e80-3601-4f9b-ae46-756dd124345f@paulmck-laptop> Precedence: bulk X-Mailing-List: rcu@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Sun, Feb 23, 2025 at 07:21:25PM -0800, Boqun Feng wrote: > 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/20250217/202502171415.8ec87c87-lkp@intel.com/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@intel.com > > 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); And we need another fix for the WARN_ONCE() above because in non-preemptible RCU on a preemptible kernel, rcu_read_lock() is just preempt_disable(). Sending both really quick. Regards, Boqun > > - 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); > > } > > [...]