From: Shuah Khan <skhan@linuxfoundation.org>
To: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Cc: corbet@lwn.net, keescook@chromium.org,
gregkh@linuxfoundation.org, linux-doc@vger.kernel.org,
linux-kernel@vger.kernel.org,
Shuah Khan <skhan@linuxfoundation.org>
Subject: Re: [PATCH v3 01/11] counters: Introduce counter_atomic* counters
Date: Wed, 14 Oct 2020 19:11:40 -0600 [thread overview]
Message-ID: <09bd23cc-56fe-3d88-4e73-31151bf76cc5@linuxfoundation.org> (raw)
In-Reply-To: <20201013132709.5740cd35@coco.lan>
On 10/13/20 5:27 AM, Mauro Carvalho Chehab wrote:
> Em Fri, 9 Oct 2020 09:55:56 -0600
> Shuah Khan <skhan@linuxfoundation.org> escreveu:
>
>> Introduce Simple atomic counters.
>>
>> There are a number of atomic_t usages in the kernel where atomic_t api
>> is used strictly for counting and not for managing object lifetime. In
>> some cases, atomic_t might not even be needed.
>>
>> The purpose of these counters is to clearly differentiate atomic_t
>> counters from atomic_t usages that guard object lifetimes, hence prone
>> to overflow and underflow errors. It allows tools that scan for underflow
>> and overflow on atomic_t usages to detect overflow and underflows to scan
>> just the cases that are prone to errors.
>>
>> Simple atomic counters api provides interfaces for simple atomic counters
>> that just count, and don't guard resource lifetimes. The interfaces are
>> built on top of atomic_t api, providing a smaller subset of atomic_t
>> interfaces necessary to support simple counters.
>>
>> Counter wraps around to INT_MIN when it overflows and should not be used
>> to guard resource lifetimes, device usage and open counts that control
>> state changes, and pm states. Overflowing to INT_MIN is consistent with
>> the atomic_t api, which it is built on top of.
>>
>> Using counter_atomic* to guard lifetimes could lead to use-after free
>> when it overflows and undefined behavior when used to manage state
>> changes and device usage/open states.
>>
>> Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
>> Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>
>
> Did you try building this with htmldocs? It produces 3 new warnings
> due to wrong usage of the "ref" tag:
>
> .../Documentation/core-api/counters.rst:46: WARNING: undefined label: test counters module (if the link has no caption the label must precede a section header)
> .../Documentation/core-api/counters.rst:49: WARNING: undefined label: selftest for counters (if the link has no caption the label must precede a section header)
> .../Documentation/core-api/counters.rst:62: WARNING: undefined label: atomic_ops (if the link has no caption the label must precede a section header)
>
I added the document to patch 1/11 and the referenced file gets added
in 2/11. Poor planning on my part.
I will fix it.
> (plus another one that I'll be sending a fixup patch anytime soon)
>
Thanks for the fix.
> Are those referring to some documents that don't exist yet uptream?
> Or are you trying to force Sphinx to generate a cross-reference for
> a C file at the tree? If it is the latter, then this won't work,
> as it will only generate cross-references for files that are placed
> inside the documentation output dir (Documentation/output, by default).
>
Th first two aren't in upstream. atomic_ops exists - I will double check
the link.
thanks,
-- Shuah
next prev parent reply other threads:[~2020-10-15 1:20 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-09 15:55 [PATCH v3 00/11] Introduce Simple atomic counters Shuah Khan
2020-10-09 15:55 ` [PATCH v3 01/11] counters: Introduce counter_atomic* counters Shuah Khan
2020-10-09 18:00 ` Kees Cook
2020-10-09 19:49 ` Peter Zijlstra
2020-10-13 11:27 ` Mauro Carvalho Chehab
2020-10-15 1:11 ` Shuah Khan [this message]
2020-10-09 15:55 ` [PATCH v3 02/11] selftests:lib:test_counters: add new test for counters Shuah Khan
2020-10-09 18:02 ` Kees Cook
2020-10-09 15:55 ` [PATCH v3 03/11] drivers/base: convert deferred_trigger_count and probe_count to counter_atomic32 Shuah Khan
2020-10-09 15:55 ` [PATCH v3 04/11] drivers/base/devcoredump: convert devcd_count " Shuah Khan
2020-10-09 18:02 ` Kees Cook
2020-10-09 19:51 ` Peter Zijlstra
2020-10-09 15:56 ` [PATCH v3 05/11] drivers/acpi: convert seqno counter_atomic32 Shuah Khan
2020-10-09 15:56 ` [PATCH v3 06/11] drivers/acpi/apei: " Shuah Khan
2020-10-09 15:56 ` [PATCH v3 07/11] drivers/android/binder: convert stats, transaction_log to counter_atomic32 Shuah Khan
2020-10-09 15:56 ` [PATCH v3 08/11] drivers/base/test/test_async_driver_probe: convert to use counter_atomic32 Shuah Khan
2020-10-09 15:56 ` [PATCH v3 09/11] drivers/char/ipmi: convert stats " Shuah Khan
2020-10-09 15:56 ` [PATCH v3 10/11] drivers/misc/vmw_vmci: convert num guest devices counter to counter_atomic32 Shuah Khan
2020-10-09 15:56 ` [PATCH v3 11/11] drivers/edac: convert pci counters " Shuah Khan
2020-10-09 18:03 ` [PATCH v3 00/11] Introduce Simple atomic counters Kees Cook
2020-10-09 19:02 ` Shuah Khan
2020-10-09 19:37 ` Peter Zijlstra
2020-10-09 20:45 ` Kees Cook
2020-10-10 11:09 ` Peter Zijlstra
2020-10-14 2:12 ` Shuah Khan
2020-10-14 9:17 ` Peter Zijlstra
2020-10-14 23:31 ` Kees Cook
2020-10-16 10:53 ` Peter Zijlstra
2020-10-16 22:51 ` Kees Cook
2020-11-10 18:49 ` Dan Carpenter
2020-10-16 21:56 ` Shuah Khan
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