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Message-ID: <56a4231d-75ab-403d-9765-064fd7d6e2d9@alu.unizg.hr>
Date: Thu, 21 Sep 2023 21:11:52 +0200
From: Mirsad Todorovac <mirsad.todorovac@....unizg.hr>
To: "Rafael J. Wysocki" <rafael@...nel.org>
Cc: linux-acpi@...r.kernel.org, acpica-devel@...ts.linuxfoundation.org,
linux-kernel@...r.kernel.org,
Robert Moore <robert.moore@...el.com>,
"Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
Len Brown <lenb@...nel.org>, Jung-uk Kim <jkim@...ebsd.org>,
Linus Torvalds <torvalds@...ux-foundation.org>,
Erik Kaneda <erik.kaneda@...el.com>,
kernel test robot <lkp@...el.com>
Subject: Re: [PATCH v3 1/1] ACPICA: utdebug: use spinlocks to fix the
data-races reported by the KCSAN
On 9/20/23 19:03, Rafael J. Wysocki wrote:
> On Wed, Sep 20, 2023 at 6:30 PM Mirsad Goran Todorovac
> <mirsad.todorovac@....unizg.hr> wrote:
>>
>> KCSAN reported hundreds of instances of data-races in ACPICA like this one:
>>
>> [ 6.994149] ==================================================================
>> [ 6.994443] BUG: KCSAN: data-race in acpi_ut_status_exit / acpi_ut_trace
>>
>> [ 6.994795] write to 0xffffffffbae5a884 of 4 bytes by task 0 on cpu 2:
>> [ 6.994944] acpi_ut_status_exit (/home/marvin/linux/kernel/torvalds2/drivers/acpi/acpica/utdebug.c:467)
>> [ 6.994957] acpi_hw_register_read (/home/marvin/linux/kernel/torvalds2/drivers/acpi/acpica/hwregs.c:563)
>> [ 6.994968] acpi_read_bit_register (/home/marvin/linux/kernel/torvalds2/drivers/acpi/acpica/hwxface.c:171)
>> [ 6.994980] acpi_idle_bm_check (/home/marvin/linux/kernel/torvalds2/drivers/acpi/processor_idle.c:511)
>> [ 6.994990] acpi_idle_enter_bm (/home/marvin/linux/kernel/torvalds2/drivers/acpi/processor_idle.c:644 (discriminator 1))
>> [ 6.995000] acpi_idle_enter (/home/marvin/linux/kernel/torvalds2/drivers/acpi/processor_idle.c:695)
>> [ 6.995010] cpuidle_enter_state (/home/marvin/linux/kernel/torvalds2/drivers/cpuidle/cpuidle.c:267)
>> [ 6.995019] cpuidle_enter (/home/marvin/linux/kernel/torvalds2/drivers/cpuidle/cpuidle.c:390)
>> [ 6.995027] call_cpuidle (/home/marvin/linux/kernel/torvalds2/kernel/sched/idle.c:135)
>> [ 6.995038] do_idle (/home/marvin/linux/kernel/torvalds2/kernel/sched/idle.c:219 /home/marvin/linux/kernel/torvalds2/kernel/sched/idle.c:282)
>> [ 6.995046] cpu_startup_entry (/home/marvin/linux/kernel/torvalds2/kernel/sched/idle.c:378 (discriminator 1))
>> [ 6.995055] start_secondary (/home/marvin/linux/kernel/torvalds2/arch/x86/kernel/smpboot.c:210 /home/marvin/linux/kernel/torvalds2/arch/x86/kernel/smpboot.c:294)
>> [ 6.995066] secondary_startup_64_no_verify (/home/marvin/linux/kernel/torvalds2/arch/x86/kernel/head_64.S:433)
>>
>> [ 6.995121] read to 0xffffffffbae5a884 of 4 bytes by task 0 on cpu 9:
>> [ 6.995267] acpi_ut_trace (/home/marvin/linux/kernel/torvalds2/drivers/acpi/acpica/utdebug.c:263)
>> [ 6.995279] acpi_hw_validate_io_request (/home/marvin/linux/kernel/torvalds2/drivers/acpi/acpica/hwvalid.c:101)
>> [ 6.995291] acpi_hw_read_port (/home/marvin/linux/kernel/torvalds2/drivers/acpi/acpica/hwvalid.c:202)
>> [ 6.995303] acpi_hw_read (/home/marvin/linux/kernel/torvalds2/drivers/acpi/acpica/hwregs.c:251)
>> [ 6.995313] acpi_hw_register_read (/home/marvin/linux/kernel/torvalds2/drivers/acpi/acpica/hwregs.c:725 /home/marvin/linux/kernel/torvalds2/drivers/acpi/acpica/hwregs.c:499)
>> [ 6.995325] acpi_read_bit_register (/home/marvin/linux/kernel/torvalds2/drivers/acpi/acpica/hwxface.c:171)
>> [ 6.995336] acpi_idle_bm_check (/home/marvin/linux/kernel/torvalds2/drivers/acpi/processor_idle.c:511)
>> [ 6.995346] acpi_idle_enter_bm (/home/marvin/linux/kernel/torvalds2/drivers/acpi/processor_idle.c:644 (discriminator 1))
>> [ 6.995356] acpi_idle_enter (/home/marvin/linux/kernel/torvalds2/drivers/acpi/processor_idle.c:695)
>> [ 6.995366] cpuidle_enter_state (/home/marvin/linux/kernel/torvalds2/drivers/cpuidle/cpuidle.c:267)
>> [ 6.995375] cpuidle_enter (/home/marvin/linux/kernel/torvalds2/drivers/cpuidle/cpuidle.c:390)
>> [ 6.995383] call_cpuidle (/home/marvin/linux/kernel/torvalds2/kernel/sched/idle.c:135)
>> [ 6.995394] do_idle (/home/marvin/linux/kernel/torvalds2/kernel/sched/idle.c:219 /home/marvin/linux/kernel/torvalds2/kernel/sched/idle.c:282)
>> [ 6.995402] cpu_startup_entry (/home/marvin/linux/kernel/torvalds2/kernel/sched/idle.c:378 (discriminator 1))
>> [ 6.995411] start_secondary (/home/marvin/linux/kernel/torvalds2/arch/x86/kernel/smpboot.c:210 /home/marvin/linux/kernel/torvalds2/arch/x86/kernel/smpboot.c:294)
>> [ 6.995422] secondary_startup_64_no_verify (/home/marvin/linux/kernel/torvalds2/arch/x86/kernel/head_64.S:433)
>>
>> [ 6.995476] value changed: 0x00000004 -> 0x00000002
>>
>> [ 6.995629] Reported by Kernel Concurrency Sanitizer on:
>> [ 6.995748] CPU: 9 PID: 0 Comm: swapper/9 Not tainted 6.6.0-rc2-kcsan-00003-g16819584c239-dirty #21
>> [ 6.995758] Hardware name: ASRock X670E PG Lightning/X670E PG Lightning, BIOS 1.21 04/26/2023
>> [ 6.995765] ==================================================================
>>
>> Please find the complete list at: https://domac.alu.unizg.hr/~mtodorov/linux/patches/acpica_utdebug/acpi_ut_status_exit.log.xz
>>
>> A number of unprotected increments:
>>
>> acpi_gbl_nesting_level++;
>>
>> and conditional statements:
>>
>> if (acpi_gbl_nesting_level) {
>> acpi_gbl_nesting_level--;
>> }
>>
>> no longer work in SMP environment.
>>
>> Proper locking like
>>
>> spin_lock(&acpi_utdebug_lock);
>> acpi_gbl_nesting_level++;
>> spin_unlock(&acpi_utdebug_lock);
>>
>> and
>>
>> spin_lock(&acpi_utdebug_lock);
>> if (acpi_gbl_nesting_level) {
>> acpi_gbl_nesting_level--;
>> }
>> spin_unlock(&acpi_utdebug_lock);
>>
>> makes these data-races go away.
>>
>> Additionally, READ_ONCE() or WRITE_ONCE() is required with the global variable
>> acpi_gbl_nesting_level to prevent unwanted read or write reordering or other funny
>> stuff the optmisers do.
>>
>> The patch eliminates KCSAN BUG warnings.
>>
>> Reported-by: Mirsad Goran Todorovac <mirsad.todorovac@....unizg.hr>
>> Fixes: 6be2d72b18649 ("ACPICA: Update for a few debug output statements")
>> Fixes: bf9b448ef8430 ("ACPICA: Debug output: Do not emit function nesting level for kernel build.")
>> Fixes: 6e875fa0480c1 ("ACPICA: Debugger: fix slight indentation issue")
>> Fixes: ^1da177e4c3f4 ("Initial git repository build.")
>> Cc: Jung-uk Kim <jkim@...eBSD.org>
>> Cc: Linus Torvalds <torvalds@...ux-foundation.org>
>> Cc: Erik Kaneda <erik.kaneda@...el.com>
>> Cc: Bob Moore <robert.moore@...el.com>
>> Cc: "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>
>> Cc: Len Brown <lenb@...nel.org>
>> Cc: linux-acpi@...r.kernel.org
>> Cc: acpica-devel@...ts.linuxfoundation.org
>> Reported-by: kernel test robot <lkp@...el.com>
>> Closes: https://lore.kernel.org/oe-kbuild-all/202309201331.S2c1JL2h-lkp@intel.com/
>> Closes: https://lore.kernel.org/oe-kbuild-all/202309201308.5ZBJFbjh-lkp@intel.com/
>> Link: https://github.com/acpica/acpica/pull/893
>> Signed-off-by: Mirsad Goran Todorovac <mirsad.todorovac@....unizg.hr>
>> ---
>> v2 -> v3:
>> Made the pull request at the ACPICA github.
>> Fixed DEFINE_SPINLOCK() undefined warning by putting it inside #ifdef ACPI_DEBUG_OUTPUT
>> ... #endif
>> Capitalised ACPICA according to the convention.
>>
>> v1 -> v2:
>> Moved the declaration of 'u32 nesting_level' inside #ifdef ACPI_APPLICATION ... #endif
>> according to the unused variable warning of the kernel test robot.
>>
>> v1:
>> Preliminary RFC version of the patch.
>>
>> drivers/acpi/acpica/utdebug.c | 49 +++++++++++++++++++++++++----------
>> 1 file changed, 35 insertions(+), 14 deletions(-)
>>
>> diff --git a/drivers/acpi/acpica/utdebug.c b/drivers/acpi/acpica/utdebug.c
>> index c5f6c85a3a09..594eee294f0f 100644
>> --- a/drivers/acpi/acpica/utdebug.c
>> +++ b/drivers/acpi/acpica/utdebug.c
>> @@ -15,8 +15,9 @@
>>
>> #define _COMPONENT ACPI_UTILITIES
>> ACPI_MODULE_NAME("utdebug")
>> -
>> #ifdef ACPI_DEBUG_OUTPUT
>> +static DEFINE_SPINLOCK(acpi_utdebug_lock);
>
> No, you can't do that in the ACPICA code. Likewise for other
> Linux-specific pieces of code in the patch below.
>
> I'd very much prefer you to send a proper problem report instead of
> sending patches like this.
I was so enthusiastic about the patch that cleared all the KCSAN data-race bug warnings,
that I must have forgot about sending one.
Patching of hundreds of annoying KCSAN acpi warnings seemed so good that I forgot about the
procedure, sorry.
I am aware that the maintainers have to carefully evaluate any contribution in order for the
kernel not becoming bloated and unstable ...
> As it stands, I'm not even sure what problem exactly this is
> attempting to address.
I hope the attached excerpt from the dmesg log will help.
> Thanks!
Anytime.
Best regards,
Mirsad Todorovac
Download attachment "acpi-kcsan-20230921-01.log.xz" of type "application/x-xz" (64264 bytes)
Download attachment "config-6.6.0-rc2-kcsan-00143-gb5cbe7c00aa0.xz" of type "application/x-xz" (58472 bytes)
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