On Wed, Dec 29, 2021 at 10:01:21PM +0800, Oliver Sang wrote:
> hi Paul,
>
> On Tue, Dec 28, 2021 at 04:06:09PM -0800, Paul E. McKenney wrote:
> > On Tue, Dec 28, 2021 at 11:11:35PM +0800, kernel test robot wrote:
> > >
> > >
> > > Greeting,
> > >
> > > FYI, we noticed the following commit (built with gcc-9):
> > >
> > > commit: 82e310033d7c21a7a88427f14e0dad78d731a5cd ("rcutorture: Enable multiple concurrent callback-flood kthreads")
> > > https://git.kernel.org/cgit/linux/kernel/git/next/linux-next.git master
> > >
> > > in testcase: rcutorture
> > > version:
> > > with following parameters:
> > >
> > > runtime: 300s
> > > test: default
> > > torture_type: rcu
> > >
> > > test-description: rcutorture is rcutorture kernel module load/unload test.
> > > test-url: https://www.kernel.org/doc/Documentation/RCU/torture.txt
> > >
> > >
> > > on test machine: qemu-system-i386 -enable-kvm -cpu SandyBridge -smp 2 -m 4G
> > >
> > > caused below changes (please refer to attached dmesg/kmsg for entire log/backtrace):
> > >
> > >
> > > +-------------------------------------------------------------------------------+------------+------------+
> > > | | 12e885433d | 82e310033d |
> > > +-------------------------------------------------------------------------------+------------+------------+
> > > | boot_successes | 95 | 47 |
> > > | boot_failures | 31 | 25 |
> > > | invoked_oom-killer:gfp_mask=0x | 5 | 4 |
> > > | Mem-Info | 10 | 16 |
> > > | WARNING:at_kernel/rcu/rcutorture.c:#rcutorture_oom_notify[rcutorture] | 24 | 15 |
> > > | EIP:rcutorture_oom_notify | 24 | 15 |
> > > | page_allocation_failure:order:#,mode:#(GFP_NOWAIT|__GFP_COMP),nodemask=(null) | 5 | 12 |
> > > | WARNING:possible_recursive_locking_detected | 0 | 15 |
> > > | WARNING:at_kernel/rcu/rcutorture.c:#rcu_torture_fwd_prog.cold[rcutorture] | 0 | 6 |
> > > | EIP:rcu_torture_fwd_prog.cold | 0 | 6 |
> > > +-------------------------------------------------------------------------------+------------+------------+
> > >
> > >
> > > If you fix the issue, kindly add following tag
> > > Reported-by: kernel test robot <oliver.sang@xxxxxxxxx>
> >
> > Good catch! Does this following patch address it?
>
> we applied below patch upon next-20211224,
> confirmed no "WARNING:possible_recursive_locking_detected" after patch.
>
> =========================================================================================
> compiler/kconfig/rootfs/runtime/tbox_group/test/testcase/torture_type:
> gcc-9/i386-randconfig-a002-20211003/debian-i386-20191205.cgz/300s/vm-snb-i386/default/rcutorture/rcu
>
> commit:
> next-20211224
> 917801238dcca ("rcutorture: Fix rcu_fwd_mutex deadlock")
>
> next-20211224 917801238dccaf61a63ffe77890
> ---------------- ---------------------------
> fail:runs %reproduction fail:runs
> | | |
> 3:100 -1% 2:100 dmesg.BUG:sleeping_function_called_from_invalid_context_at_kernel/locking/mutex.c
> 2:100 -2% :100 dmesg.BUG:workqueue_lockup-pool
> 1:100 -1% :100 dmesg.EIP:clear_user
> 2:100 2% 4:100 dmesg.EIP:rcu_torture_fwd_prog_cr
> 15:100 -3% 12:100 dmesg.EIP:rcutorture_oom_notify
> 2:100 -2% :100 dmesg.Kernel_panic-not_syncing:System_is_deadlocked_on_memory
> 9:100 -5% 4:100 dmesg.Mem-Info
> 2:100 -2% :100 dmesg.Out_of_memory_and_no_killable_processes
> 2:100 2% 4:100 dmesg.WARNING:at_kernel/rcu/rcutorture.c:#rcu_torture_fwd_prog_cr[rcutorture]
> 15:100 -3% 12:100 dmesg.WARNING:at_kernel/rcu/rcutorture.c:#rcutorture_oom_notify[rcutorture]
> 15:100 -15% :100 dmesg.WARNING:possible_recursive_locking_detected <--------
> 3:100 -1% 2:100 dmesg.invoked_oom-killer:gfp_mask=0x
> 6:100 -4% 2:100 dmesg.page_allocation_failure:order:#,mode:#(GFP_NOWAIT|__GFP_COMP),nodemask=(null)
> 100:100 0% 100:100 dmesg.sysctl_table_check_failed
Good to hear! May I add your Tested-by?
Many of the remainder appear to be due to memory exhaustion, FWIW.
Thanx, Paul
> > ------------------------------------------------------------------------
> >
> > commit dd47cbdcc2f72ba3df1248fb7fe210acca18d09c
> > Author: Paul E. McKenney <paulmck@xxxxxxxxxx>
> > Date: Tue Dec 28 15:59:38 2021 -0800
> >
> > rcutorture: Fix rcu_fwd_mutex deadlock
> >
> > The rcu_torture_fwd_cb_hist() function acquires rcu_fwd_mutex, but is
> > invoked from rcutorture_oom_notify() function, which hold this same
> > mutex across this call. This commit fixes the resulting deadlock.
> >
> > Reported-by: kernel test robot <oliver.sang@xxxxxxxxx>
> > Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxx>
> >
> > diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
> > index 918a2ea34ba13..9190dce686208 100644
> > --- a/kernel/rcu/rcutorture.c
> > +++ b/kernel/rcu/rcutorture.c
> > @@ -2184,7 +2184,6 @@ static void rcu_torture_fwd_cb_hist(struct rcu_fwd *rfp)
> > for (i = ARRAY_SIZE(rfp->n_launders_hist) - 1; i > 0; i--)
> > if (rfp->n_launders_hist[i].n_launders > 0)
> > break;
> > - mutex_lock(&rcu_fwd_mutex); // Serialize histograms.
> > pr_alert("%s: Callback-invocation histogram %d (duration %lu jiffies):",
> > __func__, rfp->rcu_fwd_id, jiffies - rfp->rcu_fwd_startat);
> > gps_old = rfp->rcu_launder_gp_seq_start;
> > @@ -2197,7 +2196,6 @@ static void rcu_torture_fwd_cb_hist(struct rcu_fwd *rfp)
> > gps_old = gps;
> > }
> > pr_cont("\n");
> > - mutex_unlock(&rcu_fwd_mutex);
> > }
> >
> > /* Callback function for continuous-flood RCU callbacks. */
> > @@ -2435,7 +2433,9 @@ static void rcu_torture_fwd_prog_cr(struct rcu_fwd *rfp)
> > n_launders, n_launders_sa,
> > n_max_gps, n_max_cbs, cver, gps);
> > atomic_long_add(n_max_cbs, &rcu_fwd_max_cbs);
> > + mutex_lock(&rcu_fwd_mutex); // Serialize histograms.
> > rcu_torture_fwd_cb_hist(rfp);
> > + mutex_unlock(&rcu_fwd_mutex);
> > }
> > schedule_timeout_uninterruptible(HZ); /* Let CBs drain. */
> > tick_dep_clear_task(current, TICK_DEP_BIT_RCU);
