From: Peter Zijlstra <peterz@infradead.org>
To: Shuah Khan <skhan@linuxfoundation.org>
Cc: corbet@lwn.net, keescook@chromium.org,
gregkh@linuxfoundation.org, linux-doc@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 01/13] seqnum_ops: Introduce Sequence Number Ops
Date: Mon, 16 Nov 2020 15:53:09 +0100 [thread overview]
Message-ID: <20201116145309.GF3121378@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <26cbcc431be5e3ab7d8e0e881d522605a27b1312.1605287778.git.skhan@linuxfoundation.org>
On Fri, Nov 13, 2020 at 10:46:03AM -0700, Shuah Khan wrote:
> +Increment interface
> +-------------------
> +
> +Increments sequence number and returns the new value. ::
> +
> + seqnum32_inc_return() --> (u32) atomic_inc_return(seqnum)
> + seqnum64_inc_return() --> (u64) atomic64_inc_return(seqnum)
Did you think about the ordering?
> +Fetch interface
> +---------------
> +
> +Fetched and returns current sequence number value. ::
> +
> + seqnum32_fetch() --> (u32) atomic_add_return(0, seqnum)
> + seqnum64_fetch() --> (u64) atomic64_add_return(0, seqnum)
That's horrible. Please explain how that is not broken garbage.
Per the fact that it is atomic, nothing prevents the counter being
incremented concurrently. There is no such thing as a 'current' sequence
number.
next prev parent reply other threads:[~2020-11-16 14:53 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
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 [this message]
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 ` [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 ` [PATCH v2 12/13] drivers/staging/unisys/visorhba: " Shuah Khan
2020-11-13 17:46 ` [PATCH v2 13/13] security/integrity/ima: converts stats to seqnum_ops Shuah Khan
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