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From: "Luck, Tony" <tony.luck@intel.com>
To: "Lobakin, Alexandr" <alexandr.lobakin@intel.com>,
	Marco Elver <elver@google.com>
Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
	Arnd Bergmann <arnd@arndb.de>, Yury Norov <yury.norov@gmail.com>,
	Mark Rutland <mark.rutland@arm.com>,
	Matt Turner <mattst88@gmail.com>, Brian Cain <bcain@quicinc.com>,
	Geert Uytterhoeven <geert@linux-m68k.org>,
	"Yoshinori Sato" <ysato@users.sourceforge.jp>,
	Rich Felker <dalias@libc.org>,
	"David S. Miller" <davem@davemloft.net>,
	Kees Cook <keescook@chromium.org>,
	"Peter Zijlstra (Intel)" <peterz@infradead.org>,
	Borislav Petkov <bp@suse.de>,
	"Greg Kroah-Hartman" <gregkh@linuxfoundation.org>,
	"linux-alpha@vger.kernel.org" <linux-alpha@vger.kernel.org>,
	"linux-hexagon@vger.kernel.org" <linux-hexagon@vger.kernel.org>,
	"linux-ia64@vger.kernel.org" <linux-ia64@vger.kernel.org>,
	"linux-m68k@lists.linux-m68k.org"
	<linux-m68k@lists.linux-m68k.org>,
	"linux-sh@vger.kernel.org" <linux-sh@vger.kernel.org>,
	"sparclinux@vger.kernel.org" <sparclinux@vger.kernel.org>,
	"linux-arch@vger.kernel.org" <linux-arch@vger.kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: RE: [PATCH v2 2/6] bitops: always define asm-generic non-atomic bitops
Date: Mon, 13 Jun 2022 16:26:49 +0000	[thread overview]
Message-ID: <c82877aa7cc244f2bf0f65dfb2b617e7@intel.com> (raw)
In-Reply-To: <20220613141947.1176100-1-alexandr.lobakin@intel.com>

>> It's listed in Documentation/atomic_bitops.txt.
>
> Oh, so my memory was actually correct that I saw it in the docs
> somewhere.
> WDYT, should I mention this here in the code (block comment) as well
> that it's atomic and must not lose `volatile` as Andy suggested or
> it's sufficient to have it in the docs (+ it's not underscored)?

I think a comment that the "volatile" is required to prevent re-ordering
is enough.

But maybe others are sufficiently clear on the meaning? I once wasted
time looking for the non-atomic __test_bit() version (to use in some code
that was already protected by a spin lock, so didn't need the overhead
of an "atomic" version) before realizing there wasn't a non-atomic one.

-Tony

WARNING: multiple messages have this Message-ID (diff)
From: "Luck, Tony" <tony.luck@intel.com>
To: "Lobakin, Alexandr" <alexandr.lobakin@intel.com>,
	Marco Elver <elver@google.com>
Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
	Arnd Bergmann <arnd@arndb.de>, Yury Norov <yury.norov@gmail.com>,
	Mark Rutland <mark.rutland@arm.com>,
	Matt Turner <mattst88@gmail.com>, Brian Cain <bcain@quicinc.com>,
	Geert Uytterhoeven <geert@linux-m68k.org>,
	Yoshinori Sato <ysato@users.sourceforge.jp>,
	Rich Felker <dalias@libc.org>,
	"David S. Miller" <davem@davemloft.net>,
	Kees Cook <keescook@chromium.org>,
	"Peter Zijlstra (Intel)" <peterz@infradead.org>,
	Borislav Petkov <bp@suse.de>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	"linux-alpha@vger.kernel.org" <linux-alpha@vger.kernel.org>,
	"linux-hexagon@vger.kernel.org" <linux-hexagon@vger.kernel.org>,
	"linux-ia64@vger.kernel.org" <linux-ia64@vger.kernel.org>,
	linux-m68k@lists.linux-m6
Subject: RE: [PATCH v2 2/6] bitops: always define asm-generic non-atomic bitops
Date: Mon, 13 Jun 2022 16:26:49 +0000	[thread overview]
Message-ID: <c82877aa7cc244f2bf0f65dfb2b617e7@intel.com> (raw)
In-Reply-To: <20220613141947.1176100-1-alexandr.lobakin@intel.com>

>> It's listed in Documentation/atomic_bitops.txt.
>
> Oh, so my memory was actually correct that I saw it in the docs
> somewhere.
> WDYT, should I mention this here in the code (block comment) as well
> that it's atomic and must not lose `volatile` as Andy suggested or
> it's sufficient to have it in the docs (+ it's not underscored)?

I think a comment that the "volatile" is required to prevent re-ordering
is enough.

But maybe others are sufficiently clear on the meaning? I once wasted
time looking for the non-atomic __test_bit() version (to use in some code
that was already protected by a spin lock, so didn't need the overhead
of an "atomic" version) before realizing there wasn't a non-atomic one.

-Tony

  parent reply	other threads:[~2022-06-13 19:01 UTC|newest]

Thread overview: 85+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-06-10 11:34 [PATCH v2 0/6] bitops: let optimize out non-atomic bitops on compile-time constants Alexander Lobakin
2022-06-10 11:34 ` Alexander Lobakin
2022-06-10 11:34 ` Alexander Lobakin
2022-06-10 11:34 ` [PATCH v2 1/6] ia64, processor: fix -Wincompatible-pointer-types in ia64_get_irr() Alexander Lobakin
2022-06-10 11:34   ` Alexander Lobakin
2022-06-10 11:34   ` Alexander Lobakin
2022-06-10 12:18   ` David Laight
2022-06-10 12:18     ` David Laight
2022-06-10 13:46   ` Andy Shevchenko
2022-06-10 13:46     ` Andy Shevchenko
2022-06-10 13:46     ` Andy Shevchenko
2022-06-15  2:59   ` Yury Norov
2022-06-15  2:59     ` Yury Norov
2022-06-15  2:59     ` Yury Norov
2022-06-10 11:34 ` [PATCH v2 2/6] bitops: always define asm-generic non-atomic bitops Alexander Lobakin
2022-06-10 11:34   ` Alexander Lobakin
2022-06-10 11:34   ` Alexander Lobakin
2022-06-10 13:50   ` Andy Shevchenko
2022-06-10 13:50     ` Andy Shevchenko
2022-06-10 13:50     ` Andy Shevchenko
2022-06-10 16:02     ` Luck, Tony
2022-06-10 16:02       ` Luck, Tony
2022-06-10 16:32       ` Marco Elver
2022-06-10 16:32         ` Marco Elver
2022-06-10 16:32         ` Marco Elver
2022-06-13 14:19         ` Alexander Lobakin
2022-06-13 14:19           ` Alexander Lobakin
2022-06-13 14:19           ` Alexander Lobakin
2022-06-13 14:33           ` Marco Elver
2022-06-13 14:33             ` Marco Elver
2022-06-13 14:33             ` Marco Elver
2022-06-15  2:47             ` Yury Norov
2022-06-15  2:47               ` Yury Norov
2022-06-15  2:47               ` Yury Norov
2022-06-15  7:46               ` Marco Elver
2022-06-15  7:46                 ` Marco Elver
2022-06-15  7:46                 ` Marco Elver
2022-06-13 16:26           ` Luck, Tony [this message]
2022-06-13 16:26             ` Luck, Tony
2022-06-13 21:29             ` David Laight
2022-06-13 21:29               ` David Laight
2022-06-10 11:34 ` [PATCH v2 3/6] bitops: unify non-atomic bitops prototypes across architectures Alexander Lobakin
2022-06-10 11:34   ` Alexander Lobakin
2022-06-10 11:34   ` Alexander Lobakin
2022-06-10 11:34 ` [PATCH v2 4/6] bitops: define const_*() versions of the non-atomics Alexander Lobakin
2022-06-10 11:34   ` Alexander Lobakin
2022-06-10 11:34   ` Alexander Lobakin
2022-06-10 13:56   ` Andy Shevchenko
2022-06-10 13:56     ` Andy Shevchenko
2022-06-10 13:56     ` Andy Shevchenko
2022-06-13 14:30     ` Alexander Lobakin
2022-06-13 14:30       ` Alexander Lobakin
2022-06-13 14:30       ` Alexander Lobakin
2022-06-15  2:57   ` Yury Norov
2022-06-15  2:57     ` Yury Norov
2022-06-15  2:57     ` Yury Norov
2022-06-15 13:55     ` Alexander Lobakin
2022-06-15 13:55       ` Alexander Lobakin
2022-06-15 13:55       ` Alexander Lobakin
2022-06-15 15:52       ` David Laight
2022-06-15 15:52         ` David Laight
2022-06-10 11:34 ` [PATCH v2 5/6] bitops: wrap non-atomic bitops with a transparent macro Alexander Lobakin
2022-06-10 11:34   ` Alexander Lobakin
2022-06-10 11:34   ` Alexander Lobakin
2022-06-10 11:34 ` [PATCH v2 6/6] bitops: let optimize out non-atomic bitops on compile-time constants Alexander Lobakin
2022-06-10 11:34   ` Alexander Lobakin
2022-06-10 11:34   ` Alexander Lobakin
2022-06-15  3:26   ` Yury Norov
2022-06-15  3:26     ` Yury Norov
2022-06-15  3:26     ` Yury Norov
2022-06-15 14:00     ` Alexander Lobakin
2022-06-15 14:00       ` Alexander Lobakin
2022-06-15 14:00       ` Alexander Lobakin
2022-06-13  7:35 ` [PATCH v2 0/6] " Geert Uytterhoeven
2022-06-13  7:35   ` Geert Uytterhoeven
2022-06-13  7:35   ` Geert Uytterhoeven
2022-06-13 14:26   ` Alexander Lobakin
2022-06-13 14:26     ` Alexander Lobakin
2022-06-13 14:26     ` Alexander Lobakin
2022-06-13 15:22     ` Geert Uytterhoeven
2022-06-13 15:22       ` Geert Uytterhoeven
2022-06-13 15:22       ` Geert Uytterhoeven
2022-06-15 14:17       ` Alexander Lobakin
2022-06-15 14:17         ` Alexander Lobakin
2022-06-15 14:17         ` Alexander Lobakin

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