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References: <20230920074158.3605-1-mirsad.todorovac@alu.unizg.hr>
In-Reply-To: <20230920074158.3605-1-mirsad.todorovac@alu.unizg.hr>
From:   "Rafael J. Wysocki" <rafael@kernel.org>
Date:   Wed, 20 Sep 2023 11:53:28 +0200
Message-ID: <CAJZ5v0j5d-jc8LRODvcjcu63URZV+EVgekQXDzN9xsWnabTaLQ@mail.gmail.com>
Subject: Re: [PATCH v2 1/1] acpica: use spinlocks to fix the data-races
 reported by the KCSAN
To:     Mirsad Goran Todorovac <mirsad.todorovac@alu.unizg.hr>
Cc:     linux-acpi@vger.kernel.org, acpica-devel@lists.linuxfoundation.org,
        linux-kernel@vger.kernel.org,
        Robert Moore <robert.moore@intel.com>,
        "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>,
        Len Brown <lenb@kernel.org>, Jung-uk Kim <jkim@freebsd.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Erik Kaneda <erik.kaneda@intel.com>,
        kernel test robot <lkp@intel.com>
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On Wed, Sep 20, 2023 at 9:44 AM Mirsad Goran Todorovac
<mirsad.todorovac@alu.unizg.hr> wrote:
>
> KCSAN reported hundreds of instances of data-races in ACPICA like this one:

If you want to make changes in the ACPICA code, the way to do that is
to submit a pull request for the upstream ACPICA project on GitHub.

Then you can resend the Linux patch with a Link: tag pointing to the
upstream pull request.

> [    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@alu.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@FreeBSD.org>
> Cc: Linus Torvalds <torvalds@linux-foundation.org>
> Cc: Erik Kaneda <erik.kaneda@intel.com>
> Cc: Bob Moore <robert.moore@intel.com>
> Cc: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>
> Cc: Len Brown <lenb@kernel.org>
> Cc: linux-acpi@vger.kernel.org
> Cc: acpica-devel@lists.linuxfoundation.org
> Signed-off-by: Mirsad Goran Todorovac <mirsad.todorovac@alu.unizg.hr>
> Reported-by: kernel test robot <lkp@intel.com>
> Closes: https://lore.kernel.org/oe-kbuild-all/202309201331.S2c1JL2h-lkp@intel.com/
> ---
> 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 | 40 ++++++++++++++++++++++++++++++-----
>  1 file changed, 35 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/acpi/acpica/utdebug.c b/drivers/acpi/acpica/utdebug.c
> index c5f6c85a3a09..1faf7dc144f0 100644
> --- a/drivers/acpi/acpica/utdebug.c
> +++ b/drivers/acpi/acpica/utdebug.c
> @@ -16,6 +16,8 @@
>  #define _COMPONENT          ACPI_UTILITIES
>  ACPI_MODULE_NAME("utdebug")
>
> +static DEFINE_SPINLOCK(acpi_utdebug_lock);
> +
>  #ifdef ACPI_DEBUG_OUTPUT
>  static acpi_thread_id acpi_gbl_previous_thread_id = (acpi_thread_id) 0xFFFFFFFF;
>  static const char *acpi_gbl_function_entry_prefix = "----Entry";
> @@ -60,13 +62,16 @@ void acpi_ut_init_stack_ptr_trace(void)
>  void acpi_ut_track_stack_ptr(void)
>  {
>         acpi_size current_sp;
> +       u32 nesting_level;
>
>         if (&current_sp < acpi_gbl_lowest_stack_pointer) {
>                 acpi_gbl_lowest_stack_pointer = &current_sp;
>         }
>
> -       if (acpi_gbl_nesting_level > acpi_gbl_deepest_nesting) {
> -               acpi_gbl_deepest_nesting = acpi_gbl_nesting_level;
> +       nesting_level = READ_ONCE(acpi_gbl_nesting_level);
> +
> +       if (nesting_level > acpi_gbl_deepest_nesting) {
> +               acpi_gbl_deepest_nesting = nesting_level;
>         }
>  }
>
> @@ -136,6 +141,7 @@ acpi_debug_print(u32 requested_debug_level,
>         va_list args;
>  #ifdef ACPI_APPLICATION
>         int fill_count;
> +       u32 nesting_level;
>  #endif
>
>         /* Check if debug output enabled */
> @@ -156,7 +162,7 @@ acpi_debug_print(u32 requested_debug_level,
>                 }
>
>                 acpi_gbl_previous_thread_id = thread_id;
> -               acpi_gbl_nesting_level = 0;
> +               WRITE_ONCE(acpi_gbl_nesting_level, 0);
>         }
>
>         /*
> @@ -176,14 +182,16 @@ acpi_debug_print(u32 requested_debug_level,
>                 acpi_os_printf("[%u] ", (u32)thread_id);
>         }
>
> -       fill_count = 48 - acpi_gbl_nesting_level -
> +       fill_count = 48 - READ_ONCE(acpi_gbl_nesting_level) -
>             strlen(acpi_ut_trim_function_name(function_name));
>         if (fill_count < 0) {
>                 fill_count = 0;
>         }
>
> +       nesting_level = READ_ONCE(acpi_gbl_nesting_level);
> +
>         acpi_os_printf("[%02d] %*s",
> -                      acpi_gbl_nesting_level, acpi_gbl_nesting_level + 1, " ");
> +                      nesting_level, nesting_level + 1, " ");
>         acpi_os_printf("%s%*s: ",
>                        acpi_ut_trim_function_name(function_name), fill_count,
>                        " ");
> @@ -260,7 +268,10 @@ acpi_ut_trace(u32 line_number,
>               const char *module_name, u32 component_id)
>  {
>
> +       spin_lock(&acpi_utdebug_lock);
>         acpi_gbl_nesting_level++;
> +       spin_unlock(&acpi_utdebug_lock);
> +
>         acpi_ut_track_stack_ptr();
>
>         /* Check if enabled up-front for performance */
> @@ -298,7 +309,10 @@ acpi_ut_trace_ptr(u32 line_number,
>                   u32 component_id, const void *pointer)
>  {
>
> +       spin_lock(&acpi_utdebug_lock);
>         acpi_gbl_nesting_level++;
> +       spin_unlock(&acpi_utdebug_lock);
> +
>         acpi_ut_track_stack_ptr();
>
>         /* Check if enabled up-front for performance */
> @@ -334,7 +348,10 @@ acpi_ut_trace_str(u32 line_number,
>                   const char *module_name, u32 component_id, const char *string)
>  {
>
> +       spin_lock(&acpi_utdebug_lock);
>         acpi_gbl_nesting_level++;
> +       spin_unlock(&acpi_utdebug_lock);
> +
>         acpi_ut_track_stack_ptr();
>
>         /* Check if enabled up-front for performance */
> @@ -370,7 +387,10 @@ acpi_ut_trace_u32(u32 line_number,
>                   const char *module_name, u32 component_id, u32 integer)
>  {
>
> +       spin_lock(&acpi_utdebug_lock);
>         acpi_gbl_nesting_level++;
> +       spin_unlock(&acpi_utdebug_lock);
> +
>         acpi_ut_track_stack_ptr();
>
>         /* Check if enabled up-front for performance */
> @@ -414,9 +434,11 @@ acpi_ut_exit(u32 line_number,
>                                  acpi_gbl_function_exit_prefix);
>         }
>
> +       spin_lock(&acpi_utdebug_lock);
>         if (acpi_gbl_nesting_level) {
>                 acpi_gbl_nesting_level--;
>         }
> +       spin_unlock(&acpi_utdebug_lock);
>  }
>
>  ACPI_EXPORT_SYMBOL(acpi_ut_exit)
> @@ -463,9 +485,11 @@ acpi_ut_status_exit(u32 line_number,
>                 }
>         }
>
> +       spin_lock(&acpi_utdebug_lock);
>         if (acpi_gbl_nesting_level) {
>                 acpi_gbl_nesting_level--;
>         }
> +       spin_unlock(&acpi_utdebug_lock);
>  }
>
>  ACPI_EXPORT_SYMBOL(acpi_ut_status_exit)
> @@ -502,9 +526,11 @@ acpi_ut_value_exit(u32 line_number,
>                                  ACPI_FORMAT_UINT64(value));
>         }
>
> +       spin_lock(&acpi_utdebug_lock);
>         if (acpi_gbl_nesting_level) {
>                 acpi_gbl_nesting_level--;
>         }
> +       spin_unlock(&acpi_utdebug_lock);
>  }
>
>  ACPI_EXPORT_SYMBOL(acpi_ut_value_exit)
> @@ -540,9 +566,11 @@ acpi_ut_ptr_exit(u32 line_number,
>                                  acpi_gbl_function_exit_prefix, ptr);
>         }
>
> +       spin_lock(&acpi_utdebug_lock);
>         if (acpi_gbl_nesting_level) {
>                 acpi_gbl_nesting_level--;
>         }
> +       spin_unlock(&acpi_utdebug_lock);
>  }
>
>  /*******************************************************************************
> @@ -577,9 +605,11 @@ acpi_ut_str_exit(u32 line_number,
>                                  acpi_gbl_function_exit_prefix, string);
>         }
>
> +       spin_lock(&acpi_utdebug_lock);
>         if (acpi_gbl_nesting_level) {
>                 acpi_gbl_nesting_level--;
>         }
> +       spin_unlock(&acpi_utdebug_lock);
>  }
>
>  /*******************************************************************************
> --
> 2.34.1
>