From: Peter Zijlstra <peterz@infradead.org>
To: "Reshetova, Elena" <elena.reshetova@intel.com>
Cc: David Windsor <dwindsor@gmail.com>,
Alexei Starovoitov <alexei.starovoitov@gmail.com>,
Kees Cook <keescook@chromium.org>,
Greg KH <gregkh@linuxfoundation.org>,
Will Deacon <will.deacon@arm.com>, Arnd Bergmann <arnd@arndb.de>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@kernel.org>, "H. Peter Anvin" <hpa@zytor.com>,
LKML <linux-kernel@vger.kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>
Subject: Re: [RFC][PATCH 2/7] kref: Add kref_read()
Date: Mon, 21 Nov 2016 16:49:15 +0100 [thread overview]
Message-ID: <20161121154915.GB3124@twins.programming.kicks-ass.net> (raw)
In-Reply-To: <2236FBA76BA1254E88B949DDB74E612B41C15583@IRSMSX102.ger.corp.intel.com>
On Mon, Nov 21, 2016 at 03:39:19PM +0000, Reshetova, Elena wrote:
> > By the way, there are several sites where the use of
> > atomic_t/atomic_wrap_t as a counter ventures beyond the standard (inc,
> > dec, add, sub, read, set) operations we're planning on implementing
> > for both refcount_t and stats_t.
>
> Speaking of non-fitting patterns. This one is quite common in
> networking code for refcounters:
>
> if (atomic_cmpxchg(&cur->refcnt, 1, 0) == 1) {} This is from
> net/netfilter/nfnetlink_acct.c, but there are similar ones in other
> places.
Cute, but weird it doesn't actually decrement if not 1.
> Also, simple atomic_dec() is used pretty much everywhere for counters,
> which we don’t have a straight match in refcount_t API.
WARN_ON(refcount_dec_and_test(refs));
And seeing how I've implememented refcount_inc() in similar terms:
WARN_ON(!refcount_inc_not_zero(refs));
It might make sense to actually provide that.
next prev parent reply other threads:[~2016-11-21 15:49 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-11-16 20:08 Alexei Starovoitov
2016-11-17 8:53 ` Peter Zijlstra
2016-11-17 16:19 ` Alexei Starovoitov
2016-11-17 16:34 ` Thomas Gleixner
2016-11-18 17:33 ` Reshetova, Elena
2016-11-19 3:47 ` Alexei Starovoitov
2016-11-21 8:18 ` Reshetova, Elena
2016-11-21 12:47 ` David Windsor
2016-11-21 15:39 ` Reshetova, Elena
2016-11-21 15:49 ` Peter Zijlstra [this message]
2016-11-21 16:00 ` Peter Zijlstra
2016-11-21 19:27 ` Reshetova, Elena
2016-11-21 20:12 ` David Windsor
2016-11-22 10:37 ` Peter Zijlstra
-- strict thread matches above, loose matches on Subject: below --
2016-11-14 17:39 [RFC][PATCH 0/7] kref improvements Peter Zijlstra
2016-11-14 17:39 ` [RFC][PATCH 2/7] kref: Add kref_read() Peter Zijlstra
2016-11-14 18:16 ` Christoph Hellwig
2016-11-15 7:28 ` Greg KH
2016-11-15 7:47 ` Peter Zijlstra
2016-11-15 7:33 ` Greg KH
2016-11-15 8:03 ` Peter Zijlstra
2016-11-15 20:53 ` Kees Cook
2016-11-16 8:21 ` Greg KH
2016-11-16 10:10 ` Peter Zijlstra
2016-11-16 10:18 ` Greg KH
2016-11-16 10:11 ` Daniel Borkmann
2016-11-16 10:19 ` Greg KH
2016-11-16 10:09 ` Peter Zijlstra
2016-11-16 18:58 ` Kees Cook
2016-11-17 8:34 ` Peter Zijlstra
2016-11-17 12:30 ` David Windsor
2016-11-17 12:43 ` Peter Zijlstra
2016-11-17 13:01 ` Reshetova, Elena
2016-11-17 13:22 ` Peter Zijlstra
2016-11-17 15:42 ` Reshetova, Elena
2016-11-17 18:02 ` Reshetova, Elena
2016-11-17 19:10 ` Peter Zijlstra
2016-11-17 19:29 ` Peter Zijlstra
2016-11-17 19:34 ` Kees Cook
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