From: Andi Kleen <andi@firstfloor.org>
To: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
Boqun Feng <boqun.feng@gmail.com>,
Peter Zijlstra <peterz@infradead.org>,
Paul Turner <pjt@google.com>, Andrew Hunter <ahh@google.com>,
Andy Lutomirski <luto@amacapital.net>,
Dave Watson <davejwatson@fb.com>,
Josh Triplett <josh@joshtriplett.org>,
Will Deacon <will.deacon@arm.com>,
linux-kernel@vger.kernel.org,
Thomas Gleixner <tglx@linutronix.de>,
Andi Kleen <andi@firstfloor.org>, Chris Lameter <cl@linux.com>,
Ingo Molnar <mingo@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>,
Ben Maurer <bmaurer@fb.com>, Steven Rostedt <rostedt@goodmis.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
Andrew Morton <akpm@linux-foundation.org>,
Russell King <linux@arm.linux.org.uk>,
Catalin Marinas <catalin.marinas@arm.com>,
Michael Kerrisk <mtk.manpages@gmail.com>,
linux-api@vger.kernel.org
Subject: Re: [RFC PATCH for 4.15 09/14] Provide cpu_opv system call
Date: Fri, 13 Oct 2017 19:50:30 -0700 [thread overview]
Message-ID: <20171014025029.GL2482@two.firstfloor.org> (raw)
In-Reply-To: <20171012230326.19984-10-mathieu.desnoyers@efficios.com>
> + pagefault_disable();
> + switch (len) {
> + case 1:
> + if (__get_user(tmp._u8, (uint8_t __user *)p))
> + goto end;
> + tmp._u8 += (uint8_t)count;
> + if (__put_user(tmp._u8, (uint8_t __user *)p))
> + goto end;
> + break;
It seems the code size could be dramatically shrunk by using a function
pointer callback for the actual operation, and then avoiding all the
copies. Since this is only a fallback this shouldn't be a problem
(and modern branch predictors are fairly good in such situations anyways)
If you really want to keep the code it would be better if you used
some macros -- i bet there's a typo in here somewhere in this
forest.
-Andi
next prev parent reply other threads:[~2017-10-14 2:50 UTC|newest]
Thread overview: 65+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-10-12 23:03 [RFC PATCH v9 for 4.15 00/14] Restartable sequences and CPU op vector system calls Mathieu Desnoyers
2017-10-12 23:03 ` [RFC PATCH v9 for 4.15 01/14] Restartable sequences system call Mathieu Desnoyers
2017-10-13 0:36 ` Linus Torvalds
2017-10-13 9:35 ` Ben Maurer
2017-10-13 18:30 ` Linus Torvalds
2017-10-13 20:54 ` Paul E. McKenney
2017-10-13 21:05 ` Linus Torvalds
2017-10-13 21:21 ` Paul E. McKenney
2017-10-13 21:36 ` Mathieu Desnoyers
2017-10-16 16:04 ` Carlos O'Donell
2017-10-16 16:46 ` Andi Kleen
2017-10-16 22:17 ` Mathieu Desnoyers
2017-10-17 16:19 ` Ben Maurer
2017-10-17 16:33 ` Mathieu Desnoyers
2017-10-17 16:41 ` Ben Maurer
2017-10-17 17:48 ` Mathieu Desnoyers
2017-10-18 6:22 ` Greg KH
2017-10-18 16:28 ` Mathieu Desnoyers
2017-10-14 3:01 ` Andi Kleen
2017-10-14 4:05 ` Linus Torvalds
2017-10-14 11:37 ` Mathieu Desnoyers
2017-10-13 12:50 ` Florian Weimer
2017-10-13 13:40 ` Mathieu Desnoyers
2017-10-13 13:56 ` Florian Weimer
2017-10-13 14:27 ` Mathieu Desnoyers
2017-10-13 17:24 ` Andy Lutomirski
2017-10-13 17:53 ` Florian Weimer
2017-10-13 18:17 ` Andy Lutomirski
2017-10-14 11:53 ` Mathieu Desnoyers
2017-10-18 16:41 ` Ben Maurer
2017-10-18 18:11 ` Mathieu Desnoyers
2017-10-19 11:35 ` Mathieu Desnoyers
2017-10-19 17:01 ` Florian Weimer
2017-10-23 17:30 ` Ben Maurer
2017-10-23 20:44 ` Mathieu Desnoyers
2017-10-12 23:03 ` [RFC PATCH for 4.15 02/14] tracing: instrument restartable sequences Mathieu Desnoyers
2017-10-12 23:03 ` [RFC PATCH for 4.15 03/14] Restartable sequences: ARM 32 architecture support Mathieu Desnoyers
2017-10-12 23:03 ` [RFC PATCH for 4.15 04/14] Restartable sequences: wire up ARM 32 system call Mathieu Desnoyers
2017-10-12 23:03 ` [RFC PATCH for 4.15 05/14] Restartable sequences: x86 32/64 architecture support Mathieu Desnoyers
2017-10-12 23:03 ` [RFC PATCH for 4.15 06/14] Restartable sequences: wire up x86 32/64 system call Mathieu Desnoyers
2017-10-12 23:03 ` [RFC PATCH for 4.15 07/14] Restartable sequences: powerpc architecture support Mathieu Desnoyers
2017-10-12 23:03 ` [RFC PATCH for 4.15 08/14] Restartable sequences: Wire up powerpc system call Mathieu Desnoyers
2017-10-12 23:03 ` [RFC PATCH for 4.15 09/14] Provide cpu_opv " Mathieu Desnoyers
2017-10-13 13:57 ` Alan Cox
2017-10-13 14:50 ` Mathieu Desnoyers
2017-10-14 14:22 ` Mathieu Desnoyers
2017-10-13 17:20 ` Andy Lutomirski
2017-10-14 2:50 ` Andi Kleen [this message]
2017-10-14 13:35 ` Mathieu Desnoyers
2017-10-12 23:03 ` [RFC PATCH for 4.15 10/14] cpu_opv: Wire up x86 32/64 " Mathieu Desnoyers
2017-10-12 23:03 ` [RFC PATCH for 4.15 11/14] cpu_opv: Wire up powerpc " Mathieu Desnoyers
2017-10-12 23:03 ` [RFC PATCH for 4.15 12/14] cpu_opv: Wire up ARM32 " Mathieu Desnoyers
2017-10-12 23:03 ` [RFC PATCH for 4.15 13/14] cpu_opv: Implement selftests Mathieu Desnoyers
2017-10-12 23:03 ` [RFC PATCH for 4.15 14/14] Restartable sequences: Provide self-tests Mathieu Desnoyers
2017-10-16 2:51 ` Michael Ellerman
2017-10-16 14:23 ` Mathieu Desnoyers
2017-10-17 10:38 ` Michael Ellerman
2017-10-17 13:50 ` Mathieu Desnoyers
2017-10-16 18:50 ` Mathieu Desnoyers
2017-10-17 10:36 ` Michael Ellerman
2017-10-17 13:50 ` Mathieu Desnoyers
2017-10-18 5:45 ` Michael Ellerman
2017-10-16 3:00 ` Michael Ellerman
2017-10-16 3:48 ` Boqun Feng
2017-10-16 11:48 ` Michael Ellerman
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