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From: David Howells <dhowells@redhat.com>
To: peterz@infradead.org
Cc: dhowells@redhat.com, Kees Cook <keescook@chromium.org>,
	Xiaoming Ni <nixiaoming@huawei.com>,
	David Windsor <dwindsor@gmail.com>,
	Hans Liljestrand <ishkamiel@gmail.com>,
	Elena Reshetova <elena.reshetova@intel.com>,
	Paul Moore <paul@paul-moore.com>,
	edumazet@google.com, paulmck@kernel.org, shakeelb@google.com,
	James Morris <jamorris@linux.microsoft.com>,
	alex.huangjianhui@huawei.com, dylix.dailei@huawei.com,
	chenzefeng2@huawei.com, linux-kernel@vger.kernel.org,
	Will Deacon <will@kernel.org>
Subject: Re: [RFC][PATCH] locking/refcount: Provide __refcount API to obtain the old value
Date: Wed, 29 Jul 2020 21:41:37 +0100	[thread overview]
Message-ID: <4041520.1596055297@warthog.procyon.org.uk> (raw)
In-Reply-To: <20200729111120.GA2638@hirez.programming.kicks-ass.net>

peterz@infradead.org wrote:

> I'm not entirely sure what you mean with interpret, provided you don't
> trigger a refcount fail, the number will be just what you expect and
> would get from refcount_read(). If you do trigger a fail, you'll get a
> negative value.

That's fine.  I seem to remember talk about the possibility that the number
wouldn't necessarily bottom out at zero - for instance if it was arranged such
that the overflow flag was set on an overflow or underflow so that it could be
trapped on (using INTO or TRAPV, for example).

David


  parent reply	other threads:[~2020-07-29 20:41 UTC|newest]

Thread overview: 26+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-06-12 18:34 [PATCH 0/3] Convert nsproxy, groups, and creds to refcount_t Kees Cook
2020-06-12 18:34 ` [PATCH 1/3] nsproxy: convert nsproxy.count " Kees Cook
2020-06-12 18:34 ` [PATCH 2/3] groups: convert group_info.usage " Kees Cook
2020-06-15  0:57   ` [groups] 67467ae141: will-it-scale.per_process_ops 4.3% improvement kernel test robot
2020-06-12 18:34 ` [PATCH 3/3] creds: convert cred.usage to refcount_t Kees Cook
2020-06-15  2:02   ` Xiaoming Ni
2020-06-15  2:10 ` [PATCH 0/3] Convert nsproxy, groups, and creds " Xiaoming Ni
2020-06-15  3:55   ` Kees Cook
2020-06-15  5:35     ` Reshetova, Elena
2020-06-15 18:08       ` Kees Cook
2020-06-18  7:39         ` Reshetova, Elena
2020-07-21 11:02         ` David Howells
2020-07-21 10:51   ` David Howells
2020-07-21 18:44     ` Kees Cook
2020-07-21 19:51       ` Peter Zijlstra
2020-07-28 10:56       ` David Howells
2020-07-29 11:11         ` [RFC][PATCH] locking/refcount: Provide __refcount API to obtain the old value peterz
2020-07-29 11:37           ` peterz
2020-07-29 19:29             ` Kees Cook
2020-07-29 19:30           ` Kees Cook
2020-08-27  7:54           ` [tip: locking/core] " tip-bot2 for Peter Zijlstra
2020-09-21 11:22           ` [RFC][PATCH] " Will Deacon
2021-01-26 11:25           ` David Howells
2020-07-29 20:41         ` David Howells [this message]
2020-07-29 20:52           ` Kees Cook
2020-07-28 11:01     ` [PATCH 0/3] Convert nsproxy, groups, and creds to refcount_t David Howells

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