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From: Qais Yousef <qais.yousef@arm.com>
To: "Paul E. McKenney" <paulmck@kernel.org>
Cc: rcu@vger.kernel.org, linux-kernel@vger.kernel.org,
	kernel-team@fb.com, mingo@kernel.org, jiangshanlai@gmail.com,
	akpm@linux-foundation.org, mathieu.desnoyers@efficios.com,
	josh@joshtriplett.org, tglx@linutronix.de, peterz@infradead.org,
	rostedt@goodmis.org, dhowells@redhat.com, edumazet@google.com,
	fweisbec@gmail.com, oleg@redhat.com, joel@joelfernandes.org,
	Yanfei Xu <yanfei.xu@windriver.com>
Subject: Re: [PATCH rcu 02/18] rcu: Fix stall-warning deadlock due to non-release of rcu_node ->lock
Date: Tue, 3 Aug 2021 15:24:58 +0100	[thread overview]
Message-ID: <20210803142458.teveyn6t2gwifdcp@e107158-lin.cambridge.arm.com> (raw)
In-Reply-To: <20210721202127.2129660-2-paulmck@kernel.org>

Hi

On 07/21/21 13:21, Paul E. McKenney wrote:
> From: Yanfei Xu <yanfei.xu@windriver.com>
> 
> If rcu_print_task_stall() is invoked on an rcu_node structure that does
> not contain any tasks blocking the current grace period, it takes an
> early exit that fails to release that rcu_node structure's lock.  This
> results in a self-deadlock, which is detected by lockdep.
> 
> To reproduce this bug:
> 
> tools/testing/selftests/rcutorture/bin/kvm.sh --allcpus --duration 3 --trust-make --configs "TREE03" --kconfig "CONFIG_PROVE_LOCKING=y" --bootargs "rcutorture.stall_cpu=30 rcutorture.stall_cpu_block=1 rcutorture.fwd_progress=0 rcutorture.test_boost=0"
> 
> This will also result in other complaints, including RCU's scheduler
> hook complaining about blocking rather than preemption and an rcutorture
> writer stall.
> 
> Only a partial RCU CPU stall warning message will be printed because of
> the self-deadlock.
> 
> This commit therefore releases the lock on the rcu_print_task_stall()
> function's early exit path.
> 
> Fixes: c583bcb8f5ed ("rcu: Don't invoke try_invoke_on_locked_down_task() with irqs disabled")
> Signed-off-by: Yanfei Xu <yanfei.xu@windriver.com>
> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
> ---

We are seeing similar stall/deadlock issue on android 5.10 kernel, is the fix
relevant here? Trying to apply the patches and test, but the problem is tricky
to reproduce so thought worth asking first.


	[ 1010.244334] rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:"}
	[ 1010.250538] rcu: \t2-...!: (42 GPs behind) idle=884/0/0x0 softirq=1646/1647 fqs=0  (false positive?)"}
	[ 1010.259746] rcu: \t3-...!: (1 ticks this GP) idle=134/0/0x0 softirq=3205/3205 fqs=0  (false positive?)"}
	[ 1010.269013] \t(detected by 4, t=6502 jiffies, g=9121, q=110)"}
	[ 1010.274621] "}
	[ 1010.276115] ============================================"}
	[ 1010.281438] WARNING: possible recursive locking detected"}
	[ 1010.286763] 5.10.43-g92fdbb553f50-ab979 #1 Not tainted"}
	[ 1010.291912] --------------------------------------------"}
	[ 1010.297235] swapper/4/0 is trying to acquire lock:"}
	[ 1010.302037] ffff8000121fe618 (rcu_node_0){-.-.}-{2:2}, at: rcu_dump_cpu_stacks+0x60/0xf8"}
	[ 1010.310183] "}
	[ 1010.310183] but task is already holding lock:"}
	[ 1010.316028] ffff8000121fe618 (rcu_node_0){-.-.}-{2:2}, at: rcu_sched_clock_irq+0x658/0xca0"}
	[ 1010.324341] "}
	[ 1010.324341] other info that might help us debug this:"}
	[ 1010.330882]  Possible unsafe locking scenario:"}
	[ 1010.330882] "}
	[ 1010.336813]        CPU0"}
	[ 1010.339263]        ----"}
	[ 1010.341713]   lock(rcu_node_0);"}
	[ 1010.344872]   lock(rcu_node_0);"}
	[ 1010.348029] "}
	[ 1010.348029]  *** DEADLOCK ***"}
	[ 1010.348029] "}
	[ 1010.353961]  May be due to missing lock nesting notation"}
	[ 1010.353961] "}
	[ 1010.360764] 1 lock held by swapper/4/0:"}
	[ 1010.364607]  #0: ffff8000121fe618 (rcu_node_0){-.-.}-{2:2}, at: rcu_sched_clock_irq+0x658/0xca0"}
	[ 1010.373359] "}
	[ 1010.373359] stack backtrace:"}
	[ 1010.377729] CPU: 4 PID: 0 Comm: swapper/4 Not tainted 5.10.43-g92fdbb553f50-ab979 #1"}
	[ 1010.385489] Hardware name: ARM Juno development board (r0) (DT)"}
	[ 1010.391421] Call trace:"}
	[ 1010.393877]  dump_backtrace+0x0/0x1c0"}
	[ 1010.397551]  show_stack+0x24/0x30"}
	[ 1010.400877]  dump_stack_lvl+0xf4/0x130"}
	[ 1010.404636]  dump_stack+0x18/0x58"}
	[ 1010.407962]  __lock_acquire+0xa18/0x1ffc"}
	[ 1010.411895]  lock_acquire.part.0+0xc8/0x30c"}
	[ 1010.416089]  lock_acquire+0x68/0x84"}
	[ 1010.419589]  _raw_spin_lock_irqsave+0x84/0x158"}
	[ 1010.424045]  rcu_dump_cpu_stacks+0x60/0xf8"}
	[ 1010.428154]  rcu_sched_clock_irq+0x8d8/0xca0"}
	[ 1010.432435]  update_process_times+0x6c/0xb0"}
	[ 1010.436632]  tick_sched_handle+0x3c/0x60"}
	[ 1010.440566]  tick_sched_timer+0x58/0xb0"}
	[ 1010.444412]  __hrtimer_run_queues+0x1a4/0x5b0"}
	[ 1010.448781]  hrtimer_interrupt+0xf4/0x2cc"}
	[ 1010.452803]  arch_timer_handler_phys+0x40/0x50"}
	[ 1010.457260]  handle_percpu_devid_irq+0x98/0x180"}
	[ 1010.461803]  __handle_domain_irq+0x80/0xec"}
	[ 1010.465911]  gic_handle_irq+0x5c/0xf0"}
	[ 1010.469583]  el1_irq+0xcc/0x180"}
	[ 1010.472735]  cpuidle_enter_state+0xe8/0x350"}
	[ 1010.476929]  cpuidle_enter+0x44/0x60"}
	[ 1010.480515]  do_idle+0x25c/0x2f0"}
	[ 1010.483751]  cpu_startup_entry+0x34/0x8c"}
	[ 1010.487687]  secondary_start_kernel+0x154/0x190"}


Thanks

--
Qais Yousef

  reply	other threads:[~2021-08-03 14:25 UTC|newest]

Thread overview: 66+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-21 20:20 [PATCH rcu 0/18] Miscellaneous fixes for v5.15 Paul E. McKenney
2021-07-21 20:21 ` [PATCH rcu 01/18] rcu: Fix to include first blocked task in stall warning Paul E. McKenney
2021-07-21 20:21 ` [PATCH rcu 02/18] rcu: Fix stall-warning deadlock due to non-release of rcu_node ->lock Paul E. McKenney
2021-08-03 14:24   ` Qais Yousef [this message]
2021-08-03 15:52     ` Paul E. McKenney
2021-08-03 16:12       ` Qais Yousef
2021-08-03 16:28         ` Paul E. McKenney
2021-08-03 16:33           ` Qais Yousef
2021-08-04 13:50           ` Qais Yousef
2021-08-04 22:33             ` Paul E. McKenney
2021-08-06  9:56               ` Qais Yousef
2021-08-06  9:57   ` Qais Yousef
2021-08-06 11:43     ` Paul E. McKenney
2021-08-06 12:33       ` Qais Yousef
2021-07-21 20:21 ` [PATCH rcu 03/18] rcu: Remove special bit at the bottom of the ->dynticks counter Paul E. McKenney
2021-07-21 20:21 ` [PATCH rcu 04/18] rcu: Weaken ->dynticks accesses and updates Paul E. McKenney
2021-07-21 20:41   ` Linus Torvalds
2021-07-21 21:25     ` Paul E. McKenney
2021-07-28 17:37   ` [PATCH v2 " Paul E. McKenney
2021-07-28 17:58     ` Linus Torvalds
2021-07-28 18:12       ` Mathieu Desnoyers
2021-07-28 18:32         ` Linus Torvalds
2021-07-28 18:39           ` Mathieu Desnoyers
2021-07-28 18:46         ` Paul E. McKenney
2021-07-28 18:46       ` Paul E. McKenney
2021-07-28 18:57         ` Linus Torvalds
2021-07-28 18:23     ` Mathieu Desnoyers
2021-07-28 18:58       ` Paul E. McKenney
2021-07-28 19:45         ` Paul E. McKenney
2021-07-28 20:03           ` Mathieu Desnoyers
2021-07-28 20:28             ` Paul E. McKenney
2021-07-29 14:41               ` Mathieu Desnoyers
2021-07-29 15:57                 ` Paul E. McKenney
2021-07-29 17:41                   ` Mathieu Desnoyers
2021-07-29 18:05                     ` Paul E. McKenney
2021-07-29 18:42                       ` Mathieu Desnoyers
2021-07-28 20:37     ` Josh Triplett
2021-07-28 20:47       ` Paul E. McKenney
2021-07-28 22:23         ` Frederic Weisbecker
2021-07-29  1:07           ` Paul E. McKenney
2021-07-29  7:58   ` [PATCH " Boqun Feng
2021-07-29 10:53     ` Frederic Weisbecker
2021-07-30  5:56       ` Boqun Feng
2021-07-30 17:18         ` Paul E. McKenney
2021-07-21 20:21 ` [PATCH rcu 05/18] rcu: Mark accesses to ->rcu_read_lock_nesting Paul E. McKenney
2021-07-21 20:21 ` [PATCH rcu 06/18] rculist: Unify documentation about missing list_empty_rcu() Paul E. McKenney
2021-07-21 20:21 ` [PATCH rcu 07/18] rcu/tree: Handle VM stoppage in stall detection Paul E. McKenney
2021-07-21 20:21 ` [PATCH rcu 08/18] rcu: Do not disable GP stall detection in rcu_cpu_stall_reset() Paul E. McKenney
2021-07-21 20:21 ` [PATCH rcu 09/18] rcu: Start timing stall repetitions after warning complete Paul E. McKenney
2021-07-21 20:21 ` [PATCH rcu 10/18] srcutiny: Mark read-side data races Paul E. McKenney
2021-07-29  8:23   ` Boqun Feng
2021-07-29 13:36     ` Paul E. McKenney
2021-07-21 20:21 ` [PATCH rcu 11/18] rcu: Mark lockless ->qsmask read in rcu_check_boost_fail() Paul E. McKenney
2021-07-29  8:54   ` Boqun Feng
2021-07-29 14:03     ` Paul E. McKenney
2021-07-30  2:28       ` Boqun Feng
2021-07-30  3:26         ` Paul E. McKenney
2021-07-21 20:21 ` [PATCH rcu 12/18] rcu: Make rcu_gp_init() and rcu_gp_fqs_loop noinline to conserve stack Paul E. McKenney
2021-07-21 20:21 ` [PATCH rcu 13/18] rcu: Remove trailing spaces and tabs Paul E. McKenney
2021-07-21 20:21 ` [PATCH rcu 14/18] rcu: Mark accesses in tree_stall.h Paul E. McKenney
2021-07-21 20:21 ` [PATCH rcu 15/18] rcu: Remove useless "ret" update in rcu_gp_fqs_loop() Paul E. McKenney
2021-08-03 16:48   ` Joe Perches
2021-08-03 17:10     ` Paul E. McKenney
2021-07-21 20:21 ` [PATCH rcu 16/18] rcu: Use per_cpu_ptr to get the pointer of per_cpu variable Paul E. McKenney
2021-07-21 20:21 ` [PATCH rcu 17/18] rcu: Explain why rcu_all_qs() is a stub in preemptible TREE RCU Paul E. McKenney
2021-07-21 20:21 ` [PATCH rcu 18/18] rcu: Print human-readable message for schedule() in RCU reader Paul E. McKenney

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