From: Andrew Cooper <andrew.cooper3@citrix.com>
To: Jan Beulich <jbeulich@suse.com>
Cc: Juergen Gross <jgross@suse.com>,
Stefano Stabellini <sstabellini@kernel.org>,
Julien Grall <julien@xen.org>, WeiLiu <wl@xen.org>,
Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
George Dunlap <George.Dunlap@eu.citrix.com>,
Tim Deegan <tim@xen.org>, Ian Jackson <ian.jackson@citrix.com>,
Xen-devel <xen-devel@lists.xenproject.org>
Subject: Re: [Xen-devel] [PATCH] xen/typesafe: Force helpers to be always_inline
Date: Tue, 1 Oct 2019 21:59:39 +0100 [thread overview]
Message-ID: <41d5ccea-b58c-ed3b-5cc8-8966d2850125@citrix.com> (raw)
In-Reply-To: <f8eb4fdc-bec8-a6cd-2657-f163169eeee5@suse.com>
On 01/10/2019 09:38, Jan Beulich wrote:
> On 30.09.2019 21:16, Andrew Cooper wrote:
>> Clang in particular has a habit of out-of-lining these and creating multiple
>> local copies of _mfn() and mfn_x(), etc. Override this behaviour.
> Is special casing the typesafe helpers then the right approach? The
> fundamental idea after all is to let the compiler decide. I certainly
> agree that not inlining such trivial functions despite the inline
> keyword looks far from optimal, but if there's such a general issue
> with clang, shouldn't we make "inline" expand to "always_inline"
> uniformly?
Inline handing is a mess.
We currently define inline to __inline__. Undoing this results in build
failures.
Linux currently defines inline to always_inline and they are desperately
trying to undo this (mis)behaviour.
There are a few uses of always_inline for safety purposes (the
speculative helpers). Most uses of always_inline look to be workarounds
for the size-of-asm bug/(mis)feature.
In an ideal world, we wouldn't need it at all, but I definitely don't
think that taking the Linux approach is a clever move. We definitely
have some static inlines which would better not being inline.
~Andrew
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next prev parent reply other threads:[~2019-10-01 21:00 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-09-30 19:16 [Xen-devel] [PATCH] xen/typesafe: Force helpers to be always_inline Andrew Cooper
2019-10-01 6:34 ` Jürgen Groß
2019-10-01 8:38 ` Jan Beulich
2019-10-01 20:59 ` Andrew Cooper [this message]
2019-10-02 8:11 ` Jan Beulich
2019-10-04 17:02 ` George Dunlap
2019-10-07 9:25 ` Jan Beulich
2019-10-21 11:10 ` George Dunlap
2019-10-23 7:27 ` Jan Beulich
2019-10-23 9:37 ` George Dunlap
2019-10-23 10:43 ` Jan Beulich
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