From: Rich Felker <dalias@libc.org>
To: Jiri Slaby <jslaby@suse.cz>
Cc: akpm@linux-foundation.org, linux-kernel@vger.kernel.org,
Richard Henderson <rth@twiddle.net>,
Ivan Kokshaysky <ink@jurassic.park.msu.ru>,
Matt Turner <mattst88@gmail.com>,
Vineet Gupta <vgupta@synopsys.com>,
Russell King <linux@armlinux.org.uk>,
Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will.deacon@arm.com>,
Richard Kuo <rkuo@codeaurora.org>,
Tony Luck <tony.luck@intel.com>,
Fenghua Yu <fenghua.yu@intel.com>,
Michal Simek <monstr@monstr.eu>,
Ralf Baechle <ralf@linux-mips.org>,
Jonas Bonn <jonas@southpole.se>,
Stefan Kristiansson <stefan.kristiansson@saunalahti.fi>,
Stafford Horne <shorne@gmail.com>,
"James E.J. Bottomley" <jejb@parisc-linux.org>,
Helge Deller <deller@gmx.de>,
Benjamin Herrenschmidt <benh@kernel.crashing.org>
Subject: Re: [PATCH 1/3] futex: remove duplicated code
Date: Mon, 06 Mar 2017 01:52:07 +0000 [thread overview]
Message-ID: <20170306015207.GN1520@brightrain.aerifal.cx> (raw)
In-Reply-To: <20170303122712.13353-1-jslaby@suse.cz>
On Fri, Mar 03, 2017 at 01:27:10PM +0100, Jiri Slaby wrote:
> There is code duplicated over all architecture's headers for
> futex_atomic_op_inuser. Namely op decoding, access_ok check for uaddr,
> and comparison of the result.
>
> Remove this duplication and leave up to the arches only the needed
> assembly which is now in arch_futex_atomic_op_inuser.
>
> Note that s390 removed access_ok check in d12a29703 ("s390/uaccess:
> remove pointless access_ok() checks") as access_ok there returns true.
> We introduce it back to the helper for the sake of simplicity (it gets
> optimized away anyway).
Overall I'm in favor of this patch, and it's close to what I had in
mind in the commit message for
00b73d8d1b7131da03aec73011a7286f566fe87f. But I'd actually like to see
it go further. These ops are mainly (only?) used for the (almost never
used) FUTEX_WAKE_OP operation, and there's very little sense in trying
to optimize them with dedicated arch-specific forms like "lock xadd".
Instead the entire logic should be in an arch-generic file, and all
the arch should need to provide is a cmpxchg-on-user-memory primitive
for it to use. On most archs, the same cmpxchg used in kernelspace
should also work for user addresses, meaning a huge amount of
unmaintained, largely untested, junk code can be removed.
Rich
WARNING: multiple messages have this Message-ID (diff)
From: Rich Felker <dalias@libc.org>
To: Jiri Slaby <jslaby@suse.cz>
Cc: akpm@linux-foundation.org, linux-kernel@vger.kernel.org,
Richard Henderson <rth@twiddle.net>,
Ivan Kokshaysky <ink@jurassic.park.msu.ru>,
Matt Turner <mattst88@gmail.com>,
Vineet Gupta <vgupta@synopsys.com>,
Russell King <linux@armlinux.org.uk>,
Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will.deacon@arm.com>,
Richard Kuo <rkuo@codeaurora.org>,
Tony Luck <tony.luck@intel.com>,
Fenghua Yu <fenghua.yu@intel.com>,
Michal Simek <monstr@monstr.eu>,
Ralf Baechle <ralf@linux-mips.org>,
Jonas Bonn <jonas@southpole.se>,
Stefan Kristiansson <stefan.kristiansson@saunalahti.fi>,
Stafford Horne <shorne@gmail.com>,
"James E.J. Bottomley" <jejb@parisc-linux.org>,
Helge Deller <deller@gmx.de>,
Benjamin Herrenschmidt <benh@kernel.crashing.org>,
Subject: Re: [PATCH 1/3] futex: remove duplicated code
Date: Sun, 5 Mar 2017 20:52:07 -0500 [thread overview]
Message-ID: <20170306015207.GN1520@brightrain.aerifal.cx> (raw)
In-Reply-To: <20170303122712.13353-1-jslaby@suse.cz>
On Fri, Mar 03, 2017 at 01:27:10PM +0100, Jiri Slaby wrote:
> There is code duplicated over all architecture's headers for
> futex_atomic_op_inuser. Namely op decoding, access_ok check for uaddr,
> and comparison of the result.
>
> Remove this duplication and leave up to the arches only the needed
> assembly which is now in arch_futex_atomic_op_inuser.
>
> Note that s390 removed access_ok check in d12a29703 ("s390/uaccess:
> remove pointless access_ok() checks") as access_ok there returns true.
> We introduce it back to the helper for the sake of simplicity (it gets
> optimized away anyway).
Overall I'm in favor of this patch, and it's close to what I had in
mind in the commit message for
00b73d8d1b7131da03aec73011a7286f566fe87f. But I'd actually like to see
it go further. These ops are mainly (only?) used for the (almost never
used) FUTEX_WAKE_OP operation, and there's very little sense in trying
to optimize them with dedicated arch-specific forms like "lock xadd".
Instead the entire logic should be in an arch-generic file, and all
the arch should need to provide is a cmpxchg-on-user-memory primitive
for it to use. On most archs, the same cmpxchg used in kernelspace
should also work for user addresses, meaning a huge amount of
unmaintained, largely untested, junk code can be removed.
Rich
WARNING: multiple messages have this Message-ID (diff)
From: Rich Felker <dalias@libc.org>
To: Jiri Slaby <jslaby@suse.cz>
Cc: akpm@linux-foundation.org, linux-kernel@vger.kernel.org,
Richard Henderson <rth@twiddle.net>,
Ivan Kokshaysky <ink@jurassic.park.msu.ru>,
Matt Turner <mattst88@gmail.com>,
Vineet Gupta <vgupta@synopsys.com>,
Russell King <linux@armlinux.org.uk>,
Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will.deacon@arm.com>,
Richard Kuo <rkuo@codeaurora.org>,
Tony Luck <tony.luck@intel.com>,
Fenghua Yu <fenghua.yu@intel.com>,
Michal Simek <monstr@monstr.eu>,
Ralf Baechle <ralf@linux-mips.org>,
Jonas Bonn <jonas@southpole.se>,
Stefan Kristiansson <stefan.kristiansson@saunalahti.fi>,
Stafford Horne <shorne@gmail.com>,
"James E.J. Bottomley" <jejb@parisc-linux.org>,
Helge Deller <deller@gmx.de>,
Benjamin Herrenschmidt <benh@kernel.crashing.org>,
Paul Mackerras <paulus@samba.org>,
Michael Ellerman <mpe@ellerman.id.au>,
Martin Schwidefsky <schwidefsky@de.ibm.com>,
Heiko Carstens <heiko.carstens@de.ibm.com>,
Yoshinori Sato <ysato@users.sourceforge.jp>,
"David S. Miller" <davem@davemloft.net>,
Chris Metcalf <cmetcalf@mellanox.com>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>,
Chris Zankel <chris@zankel.net>,
Max Filippov <jcmvbkbc@gmail.com>, Arnd Bergmann <arnd@arndb.de>,
x86@kernel.org, linux-alpha@vger.kernel.org,
linux-snps-arc@lists.infradead.org,
linux-arm-kernel@lists.infradead.org,
linux-hexagon@vger.kernel.org, linux-ia64@vger.kernel.org,
linux-mips@linux-mips.org, openrisc@lists.librecores.org,
linux-parisc@vger.kernel.org, linuxppc-dev@lists.ozlabs.org,
linux-s390@vger.kernel.org, linux-sh@vger.kernel.org,
sparclinux@vger.kernel.org, linux-xtensa@linux-xtensa.org,
linux-arch@vger.kernel.org
Subject: Re: [PATCH 1/3] futex: remove duplicated code
Date: Sun, 5 Mar 2017 20:52:07 -0500 [thread overview]
Message-ID: <20170306015207.GN1520@brightrain.aerifal.cx> (raw)
In-Reply-To: <20170303122712.13353-1-jslaby@suse.cz>
On Fri, Mar 03, 2017 at 01:27:10PM +0100, Jiri Slaby wrote:
> There is code duplicated over all architecture's headers for
> futex_atomic_op_inuser. Namely op decoding, access_ok check for uaddr,
> and comparison of the result.
>
> Remove this duplication and leave up to the arches only the needed
> assembly which is now in arch_futex_atomic_op_inuser.
>
> Note that s390 removed access_ok check in d12a29703 ("s390/uaccess:
> remove pointless access_ok() checks") as access_ok there returns true.
> We introduce it back to the helper for the sake of simplicity (it gets
> optimized away anyway).
Overall I'm in favor of this patch, and it's close to what I had in
mind in the commit message for
00b73d8d1b7131da03aec73011a7286f566fe87f. But I'd actually like to see
it go further. These ops are mainly (only?) used for the (almost never
used) FUTEX_WAKE_OP operation, and there's very little sense in trying
to optimize them with dedicated arch-specific forms like "lock xadd".
Instead the entire logic should be in an arch-generic file, and all
the arch should need to provide is a cmpxchg-on-user-memory primitive
for it to use. On most archs, the same cmpxchg used in kernelspace
should also work for user addresses, meaning a huge amount of
unmaintained, largely untested, junk code can be removed.
Rich
WARNING: multiple messages have this Message-ID (diff)
From: Rich Felker <dalias@libc.org>
To: Jiri Slaby <jslaby@suse.cz>
Cc: akpm@linux-foundation.org, linux-kernel@vger.kernel.org,
Richard Henderson <rth@twiddle.net>,
Ivan Kokshaysky <ink@jurassic.park.msu.ru>,
Matt Turner <mattst88@gmail.com>,
Vineet Gupta <vgupta@synopsys.com>,
Russell King <linux@armlinux.org.uk>,
Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will.deacon@arm.com>,
Richard Kuo <rkuo@codeaurora.org>,
Tony Luck <tony.luck@intel.com>,
Fenghua Yu <fenghua.yu@intel.com>,
Michal Simek <monstr@monstr.eu>,
Ralf Baechle <ralf@linux-mips.org>,
Jonas Bonn <jonas@southpole.se>,
Stefan Kristiansson <stefan.kristiansson@saunalahti.fi>,
Stafford Horne <shorne@gmail.com>,
"James E.J. Bottomley" <jejb@parisc-linux.org>,
Helge Deller <deller@gmx.de>,
Benjamin Herrenschmidt <benh@kernel.crashing.org>
Subject: Re: [PATCH 1/3] futex: remove duplicated code
Date: Sun, 5 Mar 2017 20:52:07 -0500 [thread overview]
Message-ID: <20170306015207.GN1520@brightrain.aerifal.cx> (raw)
In-Reply-To: <20170303122712.13353-1-jslaby@suse.cz>
On Fri, Mar 03, 2017 at 01:27:10PM +0100, Jiri Slaby wrote:
> There is code duplicated over all architecture's headers for
> futex_atomic_op_inuser. Namely op decoding, access_ok check for uaddr,
> and comparison of the result.
>
> Remove this duplication and leave up to the arches only the needed
> assembly which is now in arch_futex_atomic_op_inuser.
>
> Note that s390 removed access_ok check in d12a29703 ("s390/uaccess:
> remove pointless access_ok() checks") as access_ok there returns true.
> We introduce it back to the helper for the sake of simplicity (it gets
> optimized away anyway).
Overall I'm in favor of this patch, and it's close to what I had in
mind in the commit message for
00b73d8d1b7131da03aec73011a7286f566fe87f. But I'd actually like to see
it go further. These ops are mainly (only?) used for the (almost never
used) FUTEX_WAKE_OP operation, and there's very little sense in trying
to optimize them with dedicated arch-specific forms like "lock xadd".
Instead the entire logic should be in an arch-generic file, and all
the arch should need to provide is a cmpxchg-on-user-memory primitive
for it to use. On most archs, the same cmpxchg used in kernelspace
should also work for user addresses, meaning a huge amount of
unmaintained, largely untested, junk code can be removed.
Rich
WARNING: multiple messages have this Message-ID (diff)
From: dalias@libc.org (Rich Felker)
To: linux-snps-arc@lists.infradead.org
Subject: [PATCH 1/3] futex: remove duplicated code
Date: Sun, 5 Mar 2017 20:52:07 -0500 [thread overview]
Message-ID: <20170306015207.GN1520@brightrain.aerifal.cx> (raw)
In-Reply-To: <20170303122712.13353-1-jslaby@suse.cz>
On Fri, Mar 03, 2017@01:27:10PM +0100, Jiri Slaby wrote:
> There is code duplicated over all architecture's headers for
> futex_atomic_op_inuser. Namely op decoding, access_ok check for uaddr,
> and comparison of the result.
>
> Remove this duplication and leave up to the arches only the needed
> assembly which is now in arch_futex_atomic_op_inuser.
>
> Note that s390 removed access_ok check in d12a29703 ("s390/uaccess:
> remove pointless access_ok() checks") as access_ok there returns true.
> We introduce it back to the helper for the sake of simplicity (it gets
> optimized away anyway).
Overall I'm in favor of this patch, and it's close to what I had in
mind in the commit message for
00b73d8d1b7131da03aec73011a7286f566fe87f. But I'd actually like to see
it go further. These ops are mainly (only?) used for the (almost never
used) FUTEX_WAKE_OP operation, and there's very little sense in trying
to optimize them with dedicated arch-specific forms like "lock xadd".
Instead the entire logic should be in an arch-generic file, and all
the arch should need to provide is a cmpxchg-on-user-memory primitive
for it to use. On most archs, the same cmpxchg used in kernelspace
should also work for user addresses, meaning a huge amount of
unmaintained, largely untested, junk code can be removed.
Rich
WARNING: multiple messages have this Message-ID (diff)
From: dalias@libc.org (Rich Felker)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH 1/3] futex: remove duplicated code
Date: Sun, 5 Mar 2017 20:52:07 -0500 [thread overview]
Message-ID: <20170306015207.GN1520@brightrain.aerifal.cx> (raw)
In-Reply-To: <20170303122712.13353-1-jslaby@suse.cz>
On Fri, Mar 03, 2017 at 01:27:10PM +0100, Jiri Slaby wrote:
> There is code duplicated over all architecture's headers for
> futex_atomic_op_inuser. Namely op decoding, access_ok check for uaddr,
> and comparison of the result.
>
> Remove this duplication and leave up to the arches only the needed
> assembly which is now in arch_futex_atomic_op_inuser.
>
> Note that s390 removed access_ok check in d12a29703 ("s390/uaccess:
> remove pointless access_ok() checks") as access_ok there returns true.
> We introduce it back to the helper for the sake of simplicity (it gets
> optimized away anyway).
Overall I'm in favor of this patch, and it's close to what I had in
mind in the commit message for
00b73d8d1b7131da03aec73011a7286f566fe87f. But I'd actually like to see
it go further. These ops are mainly (only?) used for the (almost never
used) FUTEX_WAKE_OP operation, and there's very little sense in trying
to optimize them with dedicated arch-specific forms like "lock xadd".
Instead the entire logic should be in an arch-generic file, and all
the arch should need to provide is a cmpxchg-on-user-memory primitive
for it to use. On most archs, the same cmpxchg used in kernelspace
should also work for user addresses, meaning a huge amount of
unmaintained, largely untested, junk code can be removed.
Rich
next prev parent reply other threads:[~2017-03-06 1:52 UTC|newest]
Thread overview: 89+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-03-03 12:27 [PATCH 1/3] futex: remove duplicated code Jiri Slaby
2017-03-03 12:27 ` [OpenRISC] " Jiri Slaby
2017-03-03 12:27 ` Jiri Slaby
2017-03-03 12:27 ` Jiri Slaby
2017-03-03 12:27 ` Jiri Slaby
2017-03-03 12:27 ` Jiri Slaby
2017-03-03 12:27 ` [PATCH 2/3] futex: fix decoding of operation Jiri Slaby
2017-03-03 12:27 ` [PATCH 3/3] futex: make the encoded_op decoding readable Jiri Slaby
2017-03-05 7:55 ` Jiri Slaby
2017-03-03 14:08 ` [PATCH 1/3] futex: remove duplicated code Heiko Carstens
2017-03-03 14:08 ` Heiko Carstens
2017-03-03 14:08 ` Heiko Carstens
2017-03-03 14:08 ` Heiko Carstens
2017-03-03 14:08 ` Heiko Carstens
2017-03-03 14:08 ` Heiko Carstens
2017-03-03 14:48 ` Chris Metcalf
2017-03-03 14:48 ` Chris Metcalf
2017-03-03 14:48 ` Chris Metcalf
2017-03-03 14:48 ` Chris Metcalf
2017-03-03 14:48 ` Chris Metcalf
2017-03-03 14:48 ` Chris Metcalf
2017-03-03 14:48 ` Chris Metcalf
2017-03-04 12:49 ` Michael Ellerman
2017-03-04 12:49 ` Michael Ellerman
2017-03-04 12:49 ` Michael Ellerman
2017-03-04 12:49 ` Michael Ellerman
2017-03-04 12:49 ` Michael Ellerman
2017-03-04 12:49 ` Michael Ellerman
2017-03-04 12:49 ` Michael Ellerman
2017-03-04 13:05 ` Russell King - ARM Linux
2017-03-04 13:05 ` Russell King - ARM Linux
2017-03-04 13:05 ` Russell King - ARM Linux
2017-03-04 13:05 ` Russell King - ARM Linux
2017-03-04 13:05 ` Russell King - ARM Linux
2017-03-04 13:05 ` Russell King - ARM Linux
2017-03-04 19:15 ` H. Peter Anvin
2017-03-04 19:15 ` H. Peter Anvin
2017-03-04 19:15 ` H. Peter Anvin
2017-03-04 19:15 ` H. Peter Anvin
2017-03-04 19:15 ` H. Peter Anvin
2017-03-04 19:15 ` H. Peter Anvin
2017-03-04 21:38 ` Stafford Horne
2017-03-04 21:38 ` [OpenRISC] " Stafford Horne
2017-03-04 21:38 ` Stafford Horne
2017-03-04 21:38 ` Stafford Horne
2017-03-04 21:38 ` Stafford Horne
2017-03-04 21:38 ` Stafford Horne
2017-03-04 21:38 ` Stafford Horne
2017-03-04 23:03 ` H. Peter Anvin
2017-03-04 23:03 ` H. Peter Anvin
2017-03-04 23:03 ` H. Peter Anvin
2017-03-04 23:03 ` H. Peter Anvin
2017-03-04 23:03 ` H. Peter Anvin
2017-03-04 23:03 ` H. Peter Anvin
2017-03-04 23:03 ` H. Peter Anvin
2017-03-04 23:03 ` H. Peter Anvin
2017-03-04 23:08 ` H. Peter Anvin
2017-03-04 23:08 ` H. Peter Anvin
2017-03-04 23:08 ` H. Peter Anvin
2017-03-04 23:08 ` H. Peter Anvin
2017-03-04 23:08 ` H. Peter Anvin
2017-03-04 23:08 ` H. Peter Anvin
2017-03-04 23:08 ` H. Peter Anvin
2017-03-04 23:39 ` Stafford Horne
2017-03-06 8:46 ` Jiri Slaby
2017-03-06 9:13 ` H. Peter Anvin
2017-03-06 14:14 ` Geert Uytterhoeven
2017-03-04 23:08 ` H. Peter Anvin
2017-03-09 4:16 ` Rob Landley
2017-03-09 4:16 ` Rob Landley
2017-03-09 4:16 ` Rob Landley
2017-03-09 4:16 ` Rob Landley
2017-03-09 4:16 ` Rob Landley
2017-03-09 4:36 ` H. Peter Anvin
2017-03-09 4:36 ` H. Peter Anvin
2017-03-09 4:36 ` H. Peter Anvin
2017-03-09 4:36 ` H. Peter Anvin
2017-03-09 4:36 ` H. Peter Anvin
2017-03-09 4:36 ` H. Peter Anvin
2017-03-09 4:36 ` H. Peter Anvin
2017-03-09 4:36 ` H. Peter Anvin
2017-03-09 22:37 ` Rich Felker
2017-03-06 1:52 ` Rich Felker [this message]
2017-03-06 1:52 ` Rich Felker
2017-03-06 1:52 ` Rich Felker
2017-03-06 1:52 ` Rich Felker
2017-03-06 1:52 ` Rich Felker
2017-03-06 1:52 ` Rich Felker
2017-03-09 22:43 ` Vineet Gupta
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