From: Josh Triplett <josh@joshtriplett.org>
To: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Thomas Gleixner <tglx@linutronix.de>,
Paul Turner <pjt@google.com>, Andrew Hunter <ahh@google.com>,
Peter Zijlstra <peterz@infradead.org>,
linux-kernel@vger.kernel.org,
linux-api <linux-api@vger.kernel.org>,
Andy Lutomirski <luto@amacapital.net>,
Andi Kleen <andi@firstfloor.org>,
Dave Watson <davejwatson@fb.com>, Chris Lameter <cl@linux.com>,
Ingo Molnar <mingo@redhat.com>, Ben Maurer <bmaurer@fb.com>,
rostedt <rostedt@goodmis.org>,
"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
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>,
Will Deacon <will.deacon@arm.com>,
Michael Kerrisk <mtk.manpages@gmail.com>
Subject: Re: [RFC PATCH v2 1/3] getcpu_cache system call: cache CPU number of running thread
Date: Wed, 27 Jan 2016 14:11:42 -0800 [thread overview]
Message-ID: <20160127221142.GA8935@cloud> (raw)
In-Reply-To: <974364259.6329.1453930475174.JavaMail.zimbra@efficios.com>
On Wed, Jan 27, 2016 at 09:34:35PM +0000, Mathieu Desnoyers wrote:
> ----- On Jan 27, 2016, at 12:37 PM, Thomas Gleixner tglx@linutronix.de wrote:
>
> > On Wed, 27 Jan 2016, Thomas Gleixner wrote:
> >
> >> On Wed, 27 Jan 2016, Mathieu Desnoyers wrote:
> >> > ----- On Jan 27, 2016, at 12:22 PM, Thomas Gleixner tglx@linutronix.de wrote:
> >> > Sounds fair. What is the recommended typing for "ptr" then ?
> >> > uint32_t ** or uint32_t * ?
> >> >
> >> > It would be expected to pass a "uint32_t *" for the set
> >> > operation, but the "get" operation requires a "uint32_t **".
> >>
> >> Well, you can't change the types depending on the opcode, so you need to stick
> >> with **.
> >
> > Alternatively you make it:
> >
> > (opcode, *newptr, **oldptr, flags);
>
> I'm tempted to stick to (opcode, **ptr, flags), because
> other syscalls that have "*newptr", "**oldptr"
> typically have them because they save the current state
> into oldptr, and set the new state, which is really
> not the case here. To eliminate any risk of confusion,
> I am tempted to keep a single "**ptr".
>
> Unless someone has a better idea...
Either that or you could define it as "void *" and interpret it based on
flags, but that seems unfortunate; let's not imitate ioctl-style
typeless parameters. I'd stick with the double pointer and the current
behavior.
next prev parent reply other threads:[~2016-01-27 22:11 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-01-27 16:54 [RFC PATCH v2 0/3] getcpu_cache system call Mathieu Desnoyers
2016-01-27 16:54 ` [RFC PATCH v2 1/3] getcpu_cache system call: cache CPU number of running thread Mathieu Desnoyers
2016-01-27 17:20 ` Josh Triplett
2016-01-27 17:24 ` Thomas Gleixner
2016-01-27 17:36 ` Mathieu Desnoyers
2016-01-27 18:02 ` Andrew Hunter
2016-01-27 18:03 ` Josh Triplett
2016-01-27 18:43 ` Mathieu Desnoyers
2016-01-27 19:16 ` Josh Triplett
2016-01-27 21:02 ` Mathieu Desnoyers
2016-01-27 21:30 ` Josh Triplett
2016-01-27 17:22 ` Thomas Gleixner
2016-01-27 17:31 ` Mathieu Desnoyers
2016-01-27 17:34 ` Thomas Gleixner
2016-01-27 17:37 ` Thomas Gleixner
2016-01-27 21:34 ` Mathieu Desnoyers
2016-01-27 22:11 ` Josh Triplett [this message]
2016-01-27 22:47 ` Mathieu Desnoyers
2016-01-28 11:12 ` Heiko Carstens
2016-01-28 13:33 ` Mathieu Desnoyers
2016-01-28 3:12 ` Alexei Starovoitov
2016-01-28 17:41 ` Mathieu Desnoyers
2016-01-27 16:54 ` [RFC PATCH v2 2/3] getcpu_cache: wire up ARM system call Mathieu Desnoyers
2016-01-27 18:19 ` Russell King - ARM Linux
2016-01-27 18:46 ` Mathieu Desnoyers
2016-01-27 23:03 ` Mathieu Desnoyers
2016-01-27 16:54 ` [RFC PATCH v2 3/3] getcpu_cache: wire up x86 32/64 " Mathieu Desnoyers
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