From: Vincenzo Frascino <vincenzo.frascino@arm.com>
To: Catalin Marinas <catalin.marinas@arm.com>
Cc: linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org, kasan-dev@googlegroups.com,
Andrew Morton <akpm@linux-foundation.org>,
Will Deacon <will@kernel.org>, Dmitry Vyukov <dvyukov@google.com>,
Andrey Ryabinin <aryabinin@virtuozzo.com>,
Alexander Potapenko <glider@google.com>,
Marco Elver <elver@google.com>,
Evgenii Stepanov <eugenis@google.com>,
Branislav Rankov <Branislav.Rankov@arm.com>,
Andrey Konovalov <andreyknvl@google.com>,
Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Subject: Re: [PATCH v13 4/7] arm64: mte: Enable TCO in functions that can read beyond buffer limits
Date: Mon, 22 Feb 2021 12:08:07 +0000 [thread overview]
Message-ID: <c3d565da-c446-dea2-266e-ef35edabca9c@arm.com> (raw)
In-Reply-To: <20210212172128.GE7718@arm.com>
On 2/12/21 5:21 PM, Catalin Marinas wrote:
>> +
>> + /*
>> + * This function is called on each active smp core at boot
>> + * time, hence we do not need to take cpu_hotplug_lock again.
>> + */
>> + static_branch_enable_cpuslocked(&mte_async_mode);
>> }
> Sorry, I missed the cpuslocked aspect before. Is there any reason you
> need to use this API here? I suggested to add it to the
> mte_enable_kernel_sync() because kasan may at some point do this
> dynamically at run-time, so the boot-time argument doesn't hold. But
> it's also incorrect as this function will be called for hot-plugged
> CPUs as well after boot.
>
> The only reason for static_branch_*_cpuslocked() is if it's called from
> a region that already invoked cpus_read_lock() which I don't think is
> the case here.
I agree with your analysis on why static_branch_*_cpuslocked() is needed, in
fact cpus_read_lock() takes cpu_hotplug_lock as per comment on top of the line
of code.
If I try to take that lock when enabling the secondary cores I end up in the
situation below:
[ 0.283402] smp: Bringing up secondary CPUs ...
....
[ 5.890963] Call trace:
[ 5.891050] dump_backtrace+0x0/0x19c
[ 5.891212] show_stack+0x18/0x70
[ 5.891373] dump_stack+0xd0/0x12c
[ 5.891531] dequeue_task_idle+0x28/0x40
[ 5.891686] __schedule+0x45c/0x6c0
[ 5.891851] schedule+0x70/0x104
[ 5.892010] percpu_rwsem_wait+0xe8/0x104
[ 5.892174] __percpu_down_read+0x5c/0x90
[ 5.892332] percpu_down_read.constprop.0+0xbc/0xd4
[ 5.892497] cpus_read_lock+0x10/0x1c
[ 5.892660] static_key_enable+0x18/0x3c
[ 5.892823] mte_enable_kernel_async+0x40/0x70
[ 5.892988] kasan_init_hw_tags_cpu+0x50/0x60
[ 5.893144] cpu_enable_mte+0x24/0x70
[ 5.893304] verify_local_cpu_caps+0x58/0x120
[ 5.893465] check_local_cpu_capabilities+0x18/0x1f0
[ 5.893626] secondary_start_kernel+0xe0/0x190
[ 5.893790] 0x0
[ 5.893975] bad: scheduling from the idle thread!
[ 5.894065] CPU: 1 PID: 0 Comm: swapper/1 Tainted: G W
5.11.0-rc7-10587-g22cd50bcfcf-dirty #6
and the kernel panics.
Note: there is a look of msg drop in between enabling the secondary and the
first clean stack trace.
--
Regards,
Vincenzo
next prev parent reply other threads:[~2021-02-22 12:05 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-11 15:33 [PATCH v13 0/7] arm64: ARMv8.5-A: MTE: Add async mode support Vincenzo Frascino
2021-02-11 15:33 ` [PATCH v13 1/7] arm64: mte: Add asynchronous " Vincenzo Frascino
2021-02-12 21:21 ` Andrey Konovalov
2021-02-22 11:14 ` Vincenzo Frascino
2021-02-11 15:33 ` [PATCH v13 2/7] kasan: Add KASAN mode kernel parameter Vincenzo Frascino
2021-02-11 17:50 ` Andrey Konovalov
2021-02-12 11:26 ` Vincenzo Frascino
2021-02-11 15:33 ` [PATCH v13 3/7] kasan: Add report for async mode Vincenzo Frascino
2021-02-11 20:03 ` kernel test robot
2021-02-11 20:13 ` Andrey Konovalov
2021-02-12 11:25 ` Vincenzo Frascino
2021-02-12 14:47 ` Andrey Konovalov
2021-02-11 23:03 ` kernel test robot
2021-02-11 15:33 ` [PATCH v13 4/7] arm64: mte: Enable TCO in functions that can read beyond buffer limits Vincenzo Frascino
2021-02-12 17:21 ` Catalin Marinas
2021-02-22 12:08 ` Vincenzo Frascino [this message]
2021-02-22 17:58 ` Catalin Marinas
2021-02-23 10:56 ` Vincenzo Frascino
2021-02-23 12:05 ` Catalin Marinas
2021-02-23 12:22 ` Vincenzo Frascino
2021-02-23 12:49 ` Will Deacon
2021-02-23 13:14 ` Catalin Marinas
2021-02-23 14:25 ` Vincenzo Frascino
2021-02-11 15:33 ` [PATCH v13 5/7] arm64: mte: Enable async tag check fault Vincenzo Frascino
2021-02-11 15:33 ` [PATCH v13 6/7] arm64: mte: Report async tag faults before suspend Vincenzo Frascino
2021-02-12 12:00 ` Lorenzo Pieralisi
2021-02-12 12:30 ` Lorenzo Pieralisi
2021-02-12 13:05 ` Vincenzo Frascino
2021-02-12 13:19 ` Catalin Marinas
2021-02-12 17:24 ` Catalin Marinas
2021-02-11 15:33 ` [PATCH v13 7/7] kasan: don't run tests in async mode Vincenzo Frascino
2021-02-12 0:49 ` kernel test robot
2021-02-12 17:22 ` Catalin Marinas
2021-02-12 21:44 ` Andrey Konovalov
2021-02-22 11:17 ` Vincenzo Frascino
2021-02-22 13:35 ` Andrey Konovalov
2021-02-11 15:45 ` [PATCH v13 0/7] arm64: ARMv8.5-A: MTE: Add async mode support Vincenzo Frascino
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