From: "Rafael J. Wysocki" <rjw@rjwysocki.net>
To: Lv Zheng <lv.zheng@intel.com>
Cc: "Rafael J . Wysocki" <rafael.j.wysocki@intel.com>,
Len Brown <len.brown@intel.com>, Lv Zheng <zetalog@gmail.com>,
linux-kernel@vger.kernel.org, linux-acpi@vger.kernel.org,
Dan Williams <dan.j.williams@intel.com>
Subject: Re: [PATCH v4 2/4] ACPICA: Tables: Add mechanism to allow to balance late stage acpi_get_table() independently
Date: Fri, 12 May 2017 23:03:52 +0200 [thread overview]
Message-ID: <1660120.KNfsmTX9Wg@aspire.rjw.lan> (raw)
In-Reply-To: <86628bf775497ed03931e30361bb6115d78876be.1494309338.git.lv.zheng@intel.com>
On Tuesday, May 09, 2017 01:57:41 PM Lv Zheng wrote:
> For all frequent late stage acpi_get_table() clone invocations, we should
> only change them altogether, otherwise, excessive acpi_put_table() could
> unexpectedly unmap the table used by the other users. Thus the current plan
> is to change all acpi_get_table() clones together or to change none of
> them. However in practical, this is not convenient as this can prevent
> kernel developers' efforts of improving the late stage code quality before
> waiting for the ACPICA upstream to improve first.
>
> This patch adds a validation count threashold, when it is reached, the
> validation count can no longer be incremented/decremented to invalidate the
> table descriptor (means preventing table unmappings) so that acpi_put_table()
> balance changes can be done independently to each others. Lv Zheng.
>
> Cc: Dan Williams <dan.j.williams@intel.com>
> Signed-off-by: Lv Zheng <lv.zheng@intel.com>
> ---
> drivers/acpi/acpica/tbutils.c | 24 +++++++++++++++---------
> include/acpi/actbl.h | 9 +++++++++
> 2 files changed, 24 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/acpi/acpica/tbutils.c b/drivers/acpi/acpica/tbutils.c
> index 7abe665..04beafc 100644
> --- a/drivers/acpi/acpica/tbutils.c
> +++ b/drivers/acpi/acpica/tbutils.c
> @@ -416,9 +416,13 @@ acpi_tb_get_table(struct acpi_table_desc *table_desc,
> }
> }
>
> - table_desc->validation_count++;
> - if (table_desc->validation_count == 0) {
> - table_desc->validation_count--;
> + if (table_desc->validation_count < ACPI_MAX_TABLE_VALIDATIONS) {
> + table_desc->validation_count++;
> + if (table_desc->validation_count >= ACPI_MAX_TABLE_VALIDATIONS) {
> + ACPI_WARNING((AE_INFO,
> + "Table %p, Validation count overflows\n",
> + table_desc));
> + }
> }
>
> *out_table = table_desc->pointer;
> @@ -445,13 +449,15 @@ void acpi_tb_put_table(struct acpi_table_desc *table_desc)
>
> ACPI_FUNCTION_TRACE(acpi_tb_put_table);
>
> - if (table_desc->validation_count == 0) {
> - ACPI_WARNING((AE_INFO,
> - "Table %p, Validation count is zero before decrement\n",
> - table_desc));
> - return_VOID;
> + if (table_desc->validation_count < ACPI_MAX_TABLE_VALIDATIONS) {
> + table_desc->validation_count--;
> + if (table_desc->validation_count >= ACPI_MAX_TABLE_VALIDATIONS) {
Is this going to ever trigger?
We've already verified that validation_count is not 0 and that it is less than
ACPI_MAX_TABLE_VALIDATIONS and we have decremented it, so how can it be
greater than or equal to ACPI_MAX_TABLE_VALIDATIONS here?
> + ACPI_WARNING((AE_INFO,
> + "Table %p, Validation count underflows\n",
> + table_desc));
> + return_VOID;
> + }
> }
> - table_desc->validation_count--;
>
> if (table_desc->validation_count == 0) {
>
Thanks,
Rafael
next prev parent reply other threads:[~2017-05-12 21:10 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-04-27 8:22 [PATCH v2 1/2] ACPICA: Tables: Fix regression introduced by a too early mechanism enabling Lv Zheng
2017-04-27 8:22 ` [PATCH v2 2/2] ACPI: Fix memory mapping leaks in current sysfs dumpable ACPI tables support Lv Zheng
2017-04-27 22:32 ` Rafael J. Wysocki
2017-04-27 22:30 ` [PATCH v2 1/2] ACPICA: Tables: Fix regression introduced by a too early mechanism enabling Rafael J. Wysocki
2017-04-28 1:24 ` Zheng, Lv
2017-04-28 3:57 ` Zheng, Lv
2017-04-28 5:27 ` [PATCH v2 1/4] " Lv Zheng
2017-04-28 5:28 ` [PATCH v3 " Lv Zheng
2017-04-28 5:30 ` [PATCH v3 2/4] ACPICA: Tables: Add mechanism to allow to balance late stage acpi_get_table() independently Lv Zheng
2017-04-28 20:56 ` Rafael J. Wysocki
2017-05-04 7:18 ` Zheng, Lv
2017-05-04 15:45 ` Dan Williams
2017-05-05 0:53 ` Zheng, Lv
2017-05-05 20:43 ` Rafael J. Wysocki
2017-05-09 1:58 ` Zheng, Lv
2017-04-28 5:30 ` [PATCH v3 3/4] ACPI: sysfs: Fix acpi_get_table() leak Lv Zheng
2017-04-28 5:30 ` [PATCH v3 4/4] ACPI: Fix memory mapping leaks in current sysfs dumpable ACPI tables support Lv Zheng
2017-05-09 5:57 ` [PATCH v4 1/4] ACPICA: Tables: Fix regression introduced by a too early mechanism enabling Lv Zheng
2017-05-09 5:57 ` [PATCH v4 2/4] ACPICA: Tables: Add mechanism to allow to balance late stage acpi_get_table() independently Lv Zheng
2017-05-12 21:03 ` Rafael J. Wysocki [this message]
2017-05-12 21:41 ` Rafael J. Wysocki
2017-05-15 6:32 ` Zheng, Lv
2017-05-09 5:57 ` [PATCH v4 3/4] ACPI: sysfs: Fix acpi_get_table() leak Lv Zheng
2017-05-09 5:57 ` [PATCH v4 4/4] ACPI: Fix memory mapping leaks in current sysfs dumpable ACPI tables support Lv Zheng
2017-06-12 13:12 ` Rafael J. Wysocki
2017-06-07 4:54 ` [PATCH v5] ACPICA: Tables: Add mechanism to allow to balance late stage acpi_get_table() independently Lv Zheng
2017-06-07 6:41 ` Dan Williams
2017-06-07 21:14 ` Rafael J. Wysocki
2017-06-07 21:24 ` Dan Williams
2017-06-08 2:24 ` Zheng, Lv
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