From: "Roger Pau Monné" <roger.pau@citrix.com>
To: Jan Beulich <jbeulich@suse.com>
Cc: "xen-devel@lists.xenproject.org" <xen-devel@lists.xenproject.org>,
"Andrew Cooper" <andrew.cooper3@citrix.com>, Wei Liu <wl@xen.org>,
Julien Grall <julien@xen.org>,
Stefano Stabellini <sstabellini@kernel.org>,
George Dunlap <George.Dunlap@eu.citrix.com>
Subject: Re: [PATCH 1/9] build: use if_changed more consistently (and correctly) for prelink*.o
Date: Tue, 15 Sep 2020 15:46:30 +0200 [thread overview]
Message-ID: <20200915134630.GM753@Air-de-Roger> (raw)
In-Reply-To: <ae76b7d7-ea16-f668-3408-13c01a660e06@suse.com>
On Tue, Sep 15, 2020 at 02:26:34PM +0200, Jan Beulich wrote:
> On 15.09.2020 13:56, Roger Pau Monné wrote:
> > On Mon, Sep 14, 2020 at 12:15:39PM +0200, Jan Beulich wrote:
> >> Switch to $(call if_changed,ld) where possible; presumably not doing so
> >> in e321576f4047 ("xen/build: start using if_changed") right away was an
> >> oversight, as it did for Arm in (just) one case. It failed to add
> >> prelink.o to $(targets), though, causing - judging from the observed
> >> behavior on x86 - undue rebuilds of the final binary (because of
> >> prelink.o getting rebuild for $(cmd_prelink.o) being empty, in turn
> >> because of .prelink.o.cmd not getting read) during "make install-xen".
> >
> > I'm not sure I follow why prelink.o needs to be added to targets, does
> > this offer some kind of protection against rebuilds when doing make
> > install?
>
> In a way, but (as I view it) not really. It is the use of ...
>
> > The switch to if_changed LGTM.
>
> ... if_changed which requires this. .*.cmd files will only be loaded
> for anything explicitly or implicitly listed as a target. While .o
> coming from $(obj-y) get added there automatically, prelink.o is not
> something that could be recognized as needing adding, hence the
> "manual" insertion.
This seems very prone to mistakes, as you have to remember that
whatever object that uses if_changed should also be part of the
targets set, or else it will get rebuild unconditionally.
I think adding some of the above reasoning to the commit message would
be helpful IMO.
> Without .prelink.o.cmd loaded, $(if_changed ) will always arrange
> for it to get re-built, because it then will consider the command
> used to build the file to have changed (as the stored one appears to
> be empty).
Acked-by: Roger Pau Monné <roger.pau@citrix.com>
Thanks, Roger.
next prev parent reply other threads:[~2020-09-15 13:47 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-14 10:12 [PATCH 0/9] xen: beginnings of moving library-like code into an archive Jan Beulich
2020-09-14 10:15 ` [PATCH 1/9] build: use if_changed more consistently (and correctly) for prelink*.o Jan Beulich
2020-09-15 11:56 ` Roger Pau Monné
2020-09-15 12:26 ` Jan Beulich
2020-09-15 13:46 ` Roger Pau Monné [this message]
2020-09-15 15:14 ` Jan Beulich
2020-09-21 10:17 ` Ping: " Jan Beulich
2020-09-21 11:39 ` Julien Grall
2020-09-22 8:28 ` Jan Beulich
2020-09-22 9:24 ` Julien Grall
2020-09-22 10:55 ` Jan Beulich
2020-09-22 11:47 ` Julien Grall
2020-09-22 17:40 ` Stefano Stabellini
2020-09-14 10:16 ` [PATCH 2/9] lib: split _ctype[] into its own object, under lib/ Jan Beulich
2020-09-14 10:16 ` [PATCH 3/9] lib: collect library files in an archive Jan Beulich
2020-09-14 10:16 ` [PATCH 4/9] lib: move list sorting code Jan Beulich
2020-09-14 10:17 ` [PATCH 5/9] lib: move parse_size_and_unit() Jan Beulich
2020-09-22 19:41 ` Andrew Cooper
2020-09-24 7:04 ` Jan Beulich
2020-09-14 10:17 ` [PATCH 6/9] lib: move init_constructors() Jan Beulich
2020-09-14 10:18 ` [PATCH 7/9] lib: move rbtree code Jan Beulich
2020-09-14 10:18 ` [PATCH 8/9] lib: move bsearch code Jan Beulich
2020-09-22 19:34 ` Andrew Cooper
2020-09-24 7:09 ` Jan Beulich
2020-09-14 10:18 ` [PATCH 9/9] lib: move sort code Jan Beulich
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