From: will.deacon@arm.com (Will Deacon)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH] arm64: Use a raw spinlock in __install_bp_hardening_cb()
Date: Tue, 27 Nov 2018 19:15:22 +0000 [thread overview]
Message-ID: <20181127191521.GA5641@arm.com> (raw)
In-Reply-To: <20181127153521.29182-1-james.morse@arm.com>
On Tue, Nov 27, 2018 at 03:35:21PM +0000, James Morse wrote:
> __install_bp_hardening_cb() is called via stop_machine() as part
> of the cpu_enable callback. To force each CPU to take its turn
> when allocating slots, they take a spinlock.
>
> With the RT patches applied, the spinlock becomes a mutex,
> and we get warnings about sleeping while in stop_machine():
> | [ 0.319176] CPU features: detected: RAS Extension Support
> | [ 0.319950] BUG: scheduling while atomic: migration/3/36/0x00000002
> | [ 0.319955] Modules linked in:
> | [ 0.319958] Preemption disabled at:
> | [ 0.319969] [<ffff000008181ae4>] cpu_stopper_thread+0x7c/0x108
> | [ 0.319973] CPU: 3 PID: 36 Comm: migration/3 Not tainted 4.19.1-rt3-00250-g330fc2c2a880 #2
> | [ 0.319975] Hardware name: linux,dummy-virt (DT)
> | [ 0.319976] Call trace:
> | [ 0.319981] dump_backtrace+0x0/0x148
> | [ 0.319983] show_stack+0x14/0x20
> | [ 0.319987] dump_stack+0x80/0xa4
> | [ 0.319989] __schedule_bug+0x94/0xb0
> | [ 0.319991] __schedule+0x510/0x560
> | [ 0.319992] schedule+0x38/0xe8
> | [ 0.319994] rt_spin_lock_slowlock_locked+0xf0/0x278
> | [ 0.319996] rt_spin_lock_slowlock+0x5c/0x90
> | [ 0.319998] rt_spin_lock+0x54/0x58
> | [ 0.320000] enable_smccc_arch_workaround_1+0xdc/0x260
> | [ 0.320001] __enable_cpu_capability+0x10/0x20
> | [ 0.320003] multi_cpu_stop+0x84/0x108
> | [ 0.320004] cpu_stopper_thread+0x84/0x108
> | [ 0.320008] smpboot_thread_fn+0x1e8/0x2b0
> | [ 0.320009] kthread+0x124/0x128
> | [ 0.320010] ret_from_fork+0x10/0x18
>
> Switch this to a raw spinlock, as we know this is only called with
> IRQs masked.
There might be a lock-free way to do this, but this isn't a fast-path
so I've queued up your patch for 4.21.
Thanks!
Will
next prev parent reply other threads:[~2018-11-27 19:15 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-11-27 15:35 [PATCH] arm64: Use a raw spinlock in __install_bp_hardening_cb() James Morse
2018-11-27 19:15 ` Will Deacon [this message]
2018-11-28 7:51 ` Marc Zyngier
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