From: Matthew Wilcox <willy@infradead.org>
To: Shuah Khan <skhan@linuxfoundation.org>
Cc: corbet@lwn.net, keescook@chromium.org,
gregkh@linuxfoundation.org, peterz@infradead.org,
linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 01/13] seqnum_ops: Introduce Sequence Number Ops
Date: Tue, 10 Nov 2020 21:03:16 +0000 [thread overview]
Message-ID: <20201110210316.GO17076@casper.infradead.org> (raw)
In-Reply-To: <d265685c901ea81c83c18e218a29710317ab7670.1605027593.git.skhan@linuxfoundation.org>
On Tue, Nov 10, 2020 at 12:53:27PM -0700, Shuah Khan wrote:
> Sequence Numbers wrap around to INT_MIN when it overflows and should not
Why would sequence numbers be signed? I know they're built on top of
atomic_t, which is signed, but conceptually a sequence number is unsigned.
> +++ b/Documentation/core-api/seqnum_ops.rst
> @@ -0,0 +1,117 @@
> +.. SPDX-License-Identifier: GPL-2.0
> +
> +.. include:: <isonum.txt>
> +
> +.. _seqnum_ops:
> +
> +==========================
> +Sequence Number Operations
> +==========================
> +
> +:Author: Shuah Khan
> +:Copyright: |copy| 2020, The Linux Foundation
> +:Copyright: |copy| 2020, Shuah Khan <skhan@linuxfoundation.org>
> +
> +There are a number of atomic_t usages in the kernel where atomic_t api
> +is used strictly for counting sequence numbers and other statistical
> +counters and not for managing object lifetime.
You start by describing why this was introduced. I think rather, you
should start by describing what this is. You can compare and contrast
it with atomic_t later. Also, I don't think it's necessary to describe
its implementation in this document. This document should explain to
someone why they want to use this.
> +Read interface
> +--------------
> +
> +Reads and returns the current value. ::
> +
> + seqnum32_read() --> atomic_read()
> + seqnum64_read() --> atomic64_read()
> +
> +Increment interface
> +-------------------
> +
> +Increments sequence number and doesn't return the new value. ::
> +
> + seqnum32_inc() --> atomic_inc()
> + seqnum64_inc() --> atomic64_inc()
That seems odd to me. For many things, I want to know what the
sequence number was incremented to. Obviously seqnum_inc(); followed
by seqnum_read(); is racy.
Do we really want to be explicit about seqnum32 being 32-bit?
I'd be inclined to have seqnum/seqnum64 instead of seqnum32/seqnum64.
> +static inline int seqnum32_read(const struct seqnum32 *seq)
> +{
> + return atomic_read(&seq->seqnum);
> +}
> +
> +/*
> + * seqnum32_set() - set seqnum value
> + * @seq: struct seqnum32 pointer
> + * @val: new value to set
> + *
> + */
> +static inline void
> +seqnum32_set(struct seqnum32 *seq, int val)
You have some odd formatting like the above line split.
> +static inline void seqnum64_dec(
> + struct seqnum64 *seq)
That one is particularly weird.
next prev parent reply other threads:[~2020-11-10 21:03 UTC|newest]
Thread overview: 43+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-10 19:53 [PATCH 00/13] Introduce seqnum_ops Shuah Khan
2020-11-10 19:53 ` [PATCH 01/13] seqnum_ops: Introduce Sequence Number Ops Shuah Khan
2020-11-10 20:41 ` Greg KH
2020-11-10 20:43 ` Greg KH
2020-11-11 0:18 ` Kees Cook
2020-11-11 19:23 ` Shuah Khan
2020-11-12 12:36 ` Matthew Wilcox
2020-11-12 16:17 ` Shuah Khan
2020-11-12 16:45 ` Greg KH
2020-11-12 16:59 ` Shuah Khan
2020-11-12 21:27 ` Shuah Khan
2020-11-17 12:27 ` Peter Zijlstra
2020-11-10 21:03 ` Matthew Wilcox [this message]
2020-11-10 22:58 ` Shuah Khan
2020-11-11 0:20 ` Kees Cook
2020-11-11 15:42 ` Shuah Khan
2020-11-11 8:23 ` Peter Zijlstra
2020-11-11 15:56 ` Shuah Khan
2020-11-11 16:04 ` Peter Zijlstra
2020-11-11 17:34 ` Shuah Khan
2020-11-11 17:50 ` Peter Zijlstra
2020-11-11 18:28 ` Shuah Khan
2020-11-11 20:15 ` Peter Zijlstra
2020-11-12 13:29 ` Greg KH
2020-11-10 19:53 ` [PATCH 02/13] selftests:lib:test_seqnum_ops: add new test for seqnum_ops Shuah Khan
2020-11-10 19:53 ` [PATCH 03/13] drivers/acpi: convert seqno seqnum_ops Shuah Khan
2020-11-10 19:53 ` [PATCH 04/13] drivers/acpi/apei: convert seqno to seqnum_ops Shuah Khan
2020-11-10 19:53 ` [PATCH 05/13] drivers/base/test/test_async_driver_probe: convert to use seqnum_ops Shuah Khan
2020-11-10 19:53 ` [PATCH 06/13] drivers/char/ipmi: convert stats " Shuah Khan
2020-11-10 19:53 ` [PATCH 07/13] drivers/edac: convert pci counters to seqnum_ops Shuah Khan
2020-11-10 19:53 ` [PATCH 08/13] drivers/oprofile: convert stats to use seqnum_ops Shuah Khan
2020-11-10 19:53 ` [PATCH 09/13] drivers/staging/rtl8723bs: " Shuah Khan
2020-11-10 19:53 ` [PATCH 10/13] usb: usbip/vhci: convert seqno to seqnum_ops Shuah Khan
2020-11-10 19:53 ` [PATCH 11/13] drivers/staging/rtl8188eu: convert stats to use seqnum_ops Shuah Khan
2020-11-10 19:53 ` [PATCH 12/13] drivers/staging/unisys/visorhba: " Shuah Khan
2020-11-10 20:42 ` Greg KH
2020-11-10 21:02 ` Shuah Khan
2020-11-10 19:53 ` [PATCH 13/13] security/integrity/ima: converts stats to seqnum_ops Shuah Khan
2020-11-10 20:44 ` [PATCH 00/13] Introduce seqnum_ops Alan Stern
2020-11-10 22:42 ` Shuah Khan
2020-11-11 4:33 ` Matthew Wilcox
2020-11-11 16:03 ` Shuah Khan
2020-11-11 16:41 ` Matthew Wilcox
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