From: Will Deacon <will@kernel.org>
To: Qian Cai <cai@redhat.com>
Cc: "Paul E. McKenney" <paulmck@kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
Catalin Marinas <catalin.marinas@arm.com>,
linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] arm64/smp: Move rcu_cpu_starting() earlier
Date: Thu, 29 Oct 2020 09:10:45 +0000 [thread overview]
Message-ID: <20201029091045.GA29890@willie-the-truck> (raw)
In-Reply-To: <20201028182614.13655-1-cai@redhat.com>
On Wed, Oct 28, 2020 at 02:26:14PM -0400, Qian Cai wrote:
> The call to rcu_cpu_starting() in secondary_start_kernel() is not early
> enough in the CPU-hotplug onlining process, which results in lockdep
> splats as follows:
>
> WARNING: suspicious RCU usage
> -----------------------------
> kernel/locking/lockdep.c:3497 RCU-list traversed in non-reader section!!
>
> other info that might help us debug this:
>
> RCU used illegally from offline CPU!
> rcu_scheduler_active = 1, debug_locks = 1
> no locks held by swapper/1/0.
>
> Call trace:
> dump_backtrace+0x0/0x3c8
> show_stack+0x14/0x60
> dump_stack+0x14c/0x1c4
> lockdep_rcu_suspicious+0x134/0x14c
> __lock_acquire+0x1c30/0x2600
> lock_acquire+0x274/0xc48
> _raw_spin_lock+0xc8/0x140
> vprintk_emit+0x90/0x3d0
> vprintk_default+0x34/0x40
> vprintk_func+0x378/0x590
> printk+0xa8/0xd4
> __cpuinfo_store_cpu+0x71c/0x868
> cpuinfo_store_cpu+0x2c/0xc8
> secondary_start_kernel+0x244/0x318
>
> This is avoided by moving the call to rcu_cpu_starting up near the
> beginning of the secondary_start_kernel() function.
Hmm, it's not really a move though -- we'll end up calling this thing twice
afaict. It would be better to make sure we've called notify_cpu_starting()
early enough. Can we do that instead?
Will
WARNING: multiple messages have this Message-ID (diff)
From: Will Deacon <will@kernel.org>
To: Qian Cai <cai@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>,
Catalin Marinas <catalin.marinas@arm.com>,
linux-arm-kernel@lists.infradead.org,
"Paul E. McKenney" <paulmck@kernel.org>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] arm64/smp: Move rcu_cpu_starting() earlier
Date: Thu, 29 Oct 2020 09:10:45 +0000 [thread overview]
Message-ID: <20201029091045.GA29890@willie-the-truck> (raw)
In-Reply-To: <20201028182614.13655-1-cai@redhat.com>
On Wed, Oct 28, 2020 at 02:26:14PM -0400, Qian Cai wrote:
> The call to rcu_cpu_starting() in secondary_start_kernel() is not early
> enough in the CPU-hotplug onlining process, which results in lockdep
> splats as follows:
>
> WARNING: suspicious RCU usage
> -----------------------------
> kernel/locking/lockdep.c:3497 RCU-list traversed in non-reader section!!
>
> other info that might help us debug this:
>
> RCU used illegally from offline CPU!
> rcu_scheduler_active = 1, debug_locks = 1
> no locks held by swapper/1/0.
>
> Call trace:
> dump_backtrace+0x0/0x3c8
> show_stack+0x14/0x60
> dump_stack+0x14c/0x1c4
> lockdep_rcu_suspicious+0x134/0x14c
> __lock_acquire+0x1c30/0x2600
> lock_acquire+0x274/0xc48
> _raw_spin_lock+0xc8/0x140
> vprintk_emit+0x90/0x3d0
> vprintk_default+0x34/0x40
> vprintk_func+0x378/0x590
> printk+0xa8/0xd4
> __cpuinfo_store_cpu+0x71c/0x868
> cpuinfo_store_cpu+0x2c/0xc8
> secondary_start_kernel+0x244/0x318
>
> This is avoided by moving the call to rcu_cpu_starting up near the
> beginning of the secondary_start_kernel() function.
Hmm, it's not really a move though -- we'll end up calling this thing twice
afaict. It would be better to make sure we've called notify_cpu_starting()
early enough. Can we do that instead?
Will
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next prev parent reply other threads:[~2020-10-29 9:10 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-28 18:26 [PATCH] arm64/smp: Move rcu_cpu_starting() earlier Qian Cai
2020-10-28 18:26 ` Qian Cai
2020-10-28 21:00 ` Paul E. McKenney
2020-10-28 21:00 ` Paul E. McKenney
2020-10-29 9:10 ` Will Deacon [this message]
2020-10-29 9:10 ` Will Deacon
2020-10-29 13:17 ` Qian Cai
2020-10-29 13:17 ` Qian Cai
2020-10-30 8:15 ` Will Deacon
2020-10-30 8:15 ` Will Deacon
2020-10-29 14:09 ` Paul E. McKenney
2020-10-29 14:09 ` Paul E. McKenney
2020-10-30 16:33 ` Will Deacon
2020-10-30 16:33 ` Will Deacon
2020-11-05 22:22 ` Will Deacon
2020-11-05 22:22 ` Will Deacon
2020-11-05 23:02 ` Qian Cai
2020-11-05 23:02 ` Qian Cai
2020-11-05 23:28 ` Paul E. McKenney
2020-11-05 23:28 ` Paul E. McKenney
2020-11-06 2:15 ` Qian Cai
2020-11-06 2:15 ` Qian Cai
2020-11-06 4:07 ` Paul E. McKenney
2020-11-06 4:07 ` Paul E. McKenney
2020-11-06 10:37 ` Will Deacon
2020-11-06 10:37 ` Will Deacon
2020-11-06 12:48 ` Qian Cai
2020-11-06 12:48 ` Qian Cai
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