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* [PATCH v2 00/13] Introduce seqnum_ops
@ 2020-11-13 17:46 Shuah Khan
  2020-11-13 17:46 ` [PATCH v2 01/13] seqnum_ops: Introduce Sequence Number Ops Shuah Khan
                   ` (12 more replies)
  0 siblings, 13 replies; 30+ messages in thread
From: Shuah Khan @ 2020-11-13 17:46 UTC (permalink / raw)
  To: corbet, keescook, gregkh, peterz, rafael, lenb, james.morse,
	tony.luck, bp, minyard, arnd, mchehab, rric, valentina.manea.m,
	shuah, zohar, dmitry.kasatkin, jmorris, serge
  Cc: Shuah Khan, linux-doc, linux-kernel, linux-kselftest, linux-acpi,
	openipmi-developer, linux-edac, linux-usb, linux-integrity,
	linux-security-module

Sequence Number api provides interfaces for unsigned atomic up counters
leveraging atomic_t and atomic64_t ops underneath.

There are a number of atomic_t usages in the kernel where atomic_t api
is used for counting sequence numbers and other statistical counters.
Several of these usages, convert atomic_read() and atomic_inc_return()
return values to unsigned. Introducing sequence number ops supports
these use-cases with a standard core-api.

The atomic_t api provides a wide range of atomic operations as a base
api to implement atomic counters, bitops, spinlock interfaces. The usages
also evolved into being used for resource lifetimes and state management.
The refcount_t api was introduced to address resource lifetime problems
related to atomic_t wrapping. There is a large overlap between the
atomic_t api used for resource lifetimes and just counters, stats, and
sequence numbers. It has become difficult to differentiate between the
atomic_t usages that should be converted to refcount_t and the ones that
can be left alone. Introducing seqnum_ops to wrap the usages that are
stats, counters, sequence numbers makes it easier for 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.

In addition, to supporting sequence number use-cases, Sequence Number Ops
helps differentiate atomic_t counter usages from atomic_t usages that guard
object lifetimes, hence prone to overflow and underflow errors from up
counting use-cases. It becomes easier for 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.

Changes since v1:
- Removed dec based on Greg KH's comments
- Removed read/set/inc based on the discussion with Peter Zijlstra
- Interfaces are restricted to init, increment and return new value,
  and fetch current value.
- Interfaces return u32 and u64 - a few reviewers suggested unsigned.
  After reviewing a few use-cases, I determined this is a good path
  forward. It adds unsigned atomic support that doesn't exist now,
  and simplifies code in drivers that currently convert atomic_t return
  values to unsigned. All the drivers changes included in this series
  used to convert atomic_t returns to unsigned.

Patch v1 thread:
https://lore.kernel.org/lkml/cover.1605027593.git.skhan@linuxfoundation.org/

Counters thread:
lore.kernel.org/lkml/cover.1602209970.git.skhan@linuxfoundation.org

Shuah Khan (13):
  seqnum_ops: Introduce Sequence Number Ops
  selftests: lib:test_seqnum_ops: add new test for seqnum_ops
  drivers/acpi: convert seqno seqnum_ops
  drivers/acpi/apei: convert seqno to seqnum_ops
  drivers/base/test/test_async_driver_probe: convert to use seqnum_ops
  drivers/char/ipmi: convert stats to use seqnum_ops
  drivers/edac: convert pci counters to seqnum_ops
  drivers/oprofile: convert stats to use seqnum_ops
  drivers/staging/rtl8723bs: convert stats to use seqnum_ops
  usb: usbip/vhci: convert seqno to seqnum_ops
  drivers/staging/rtl8188eu: convert stats to use seqnum_ops
  drivers/staging/unisys/visorhba: convert stats to use seqnum_ops
  security/integrity/ima: converts stats to seqnum_ops

 Documentation/core-api/atomic_ops.rst         |   4 +
 Documentation/core-api/index.rst              |   1 +
 Documentation/core-api/seqnum_ops.rst         |  89 +++++++++++++
 MAINTAINERS                                   |   8 ++
 drivers/acpi/acpi_extlog.c                    |   8 +-
 drivers/acpi/apei/ghes.c                      |   8 +-
 drivers/base/test/test_async_driver_probe.c   |  28 +++--
 drivers/char/ipmi/ipmi_msghandler.c           |   9 +-
 drivers/char/ipmi/ipmi_si_intf.c              |   9 +-
 drivers/char/ipmi/ipmi_ssif.c                 |   9 +-
 drivers/edac/edac_pci.h                       |   5 +-
 drivers/edac/edac_pci_sysfs.c                 |  30 ++---
 drivers/oprofile/buffer_sync.c                |   9 +-
 drivers/oprofile/event_buffer.c               |   3 +-
 drivers/oprofile/oprof.c                      |   3 +-
 drivers/oprofile/oprofile_stats.c             |  11 +-
 drivers/oprofile/oprofile_stats.h             |  11 +-
 drivers/oprofile/oprofilefs.c                 |   3 +-
 drivers/staging/rtl8188eu/core/rtw_mlme_ext.c |  23 +++-
 .../staging/rtl8188eu/include/rtw_mlme_ext.h  |   3 +-
 drivers/staging/rtl8723bs/core/rtw_cmd.c      |   3 +-
 drivers/staging/rtl8723bs/core/rtw_mlme_ext.c |  33 +++--
 drivers/staging/rtl8723bs/include/rtw_cmd.h   |   3 +-
 .../staging/rtl8723bs/include/rtw_mlme_ext.h  |   3 +-
 .../staging/unisys/visorhba/visorhba_main.c   |  21 ++--
 drivers/usb/usbip/vhci.h                      |   3 +-
 drivers/usb/usbip/vhci_hcd.c                  |   7 +-
 drivers/usb/usbip/vhci_rx.c                   |   5 +-
 include/linux/oprofile.h                      |   3 +-
 include/linux/seqnum_ops.h                    | 118 +++++++++++++++++
 lib/Kconfig                                   |   9 ++
 lib/Makefile                                  |   1 +
 lib/test_seqnum_ops.c                         | 119 ++++++++++++++++++
 security/integrity/ima/ima.h                  |   5 +-
 security/integrity/ima/ima_api.c              |   3 +-
 security/integrity/ima/ima_fs.c               |   5 +-
 security/integrity/ima/ima_queue.c            |   7 +-
 tools/testing/selftests/lib/Makefile          |   1 +
 tools/testing/selftests/lib/config            |   1 +
 .../testing/selftests/lib/test_seqnum_ops.sh  |  10 ++
 40 files changed, 524 insertions(+), 110 deletions(-)
 create mode 100644 Documentation/core-api/seqnum_ops.rst
 create mode 100644 include/linux/seqnum_ops.h
 create mode 100644 lib/test_seqnum_ops.c
 create mode 100755 tools/testing/selftests/lib/test_seqnum_ops.sh

-- 
2.27.0


^ permalink raw reply	[flat|nested] 30+ messages in thread

end of thread, other threads:[~2020-11-17 18:24 UTC | newest]

Thread overview: 30+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2020-11-13 17:46 [PATCH v2 00/13] Introduce seqnum_ops Shuah Khan
2020-11-13 17:46 ` [PATCH v2 01/13] seqnum_ops: Introduce Sequence Number Ops Shuah Khan
2020-11-13 21:03   ` Matthew Wilcox
2020-11-16 14:49     ` Peter Zijlstra
2020-11-16 14:58       ` Peter Zijlstra
2020-11-17 14:50         ` Shuah Khan
2020-11-17 15:21           ` Peter Zijlstra
2020-11-17 16:34     ` Shuah Khan
2020-11-17 17:38       ` Matthew Wilcox
2020-11-17 18:23         ` Shuah Khan
2020-11-17 18:24         ` Shuah Khan
2020-11-16 14:53   ` Peter Zijlstra
2020-11-17 16:15     ` Shuah Khan
2020-11-13 17:46 ` [PATCH v2 02/13] selftests: lib:test_seqnum_ops: add new test for seqnum_ops Shuah Khan
2020-11-13 17:46 ` [PATCH v2 03/13] drivers/acpi: convert seqno seqnum_ops Shuah Khan
2020-11-13 17:46 ` [PATCH v2 04/13] drivers/acpi/apei: convert seqno to seqnum_ops Shuah Khan
2020-11-13 17:46 ` [PATCH v2 05/13] drivers/base/test/test_async_driver_probe: convert to use seqnum_ops Shuah Khan
2020-11-13 17:46 ` [PATCH v2 06/13] drivers/char/ipmi: convert stats " Shuah Khan
2020-11-13 17:46 ` [PATCH v2 07/13] drivers/edac: convert pci counters to seqnum_ops Shuah Khan
2020-11-13 17:46 ` [PATCH v2 08/13] drivers/oprofile: convert stats to use seqnum_ops Shuah Khan
2020-11-13 17:46 ` [PATCH v2 09/13] drivers/staging/rtl8723bs: " Shuah Khan
2020-11-13 17:46   ` Shuah Khan
2020-11-13 17:46 ` [PATCH v2 10/13] usb: usbip/vhci: convert seqno to seqnum_ops Shuah Khan
2020-11-13 17:46 ` [PATCH v2 11/13] drivers/staging/rtl8188eu: convert stats to use seqnum_ops Shuah Khan
2020-11-13 17:46   ` Shuah Khan
2020-11-13 17:46 ` [PATCH v2 12/13] drivers/staging/unisys/visorhba: " Shuah Khan
2020-11-13 17:46   ` Shuah Khan
2020-11-13 17:46 ` [PATCH v2 13/13] security/integrity/ima: converts stats to seqnum_ops Shuah Khan
2020-11-14 16:11   ` kernel test robot
2020-11-14 16:11     ` kernel test robot

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