From: Igor Stoppa <igor.stoppa@gmail.com>
To: Arnd Bergmann <arnd@arndb.de>
Cc: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
igor.stoppa@huawei.com, Aaro Koskinen <aaro.koskinen@iki.fi>,
Alasdair Kergon <agk@redhat.com>,
Al Viro <viro@zeniv.linux.org.uk>,
Andrew Jeffery <andrew@aj.id.au>,
Archit Taneja <architt@codeaurora.org>,
asolokha@kb.kras.ru, bvanassche@acm.org,
Benjamin Herrenschmidt <benh@kernel.crashing.org>,
chien.tin.tung@intel.com, chunkeey@googlemail.com,
Christoph Lameter <cl@linux.com>, David Airlie <airlied@linux.ie>,
David Daney <ddaney@caviumnetworks.com>,
Dennis Zhou <dennisszhou@gmail.com>,
dima@arista.com, Doug Ledford <dledford@redhat.com>,
"Latif, Faisal" <faisal.latif@intel.com>,
gregkh <gregkh@linuxfoundation.org>,
Daode Huang <huangdaode@hisilicon.com>,
Inaky Perez-Gonzalez <inaky.perez-gonzalez@intel.com>,
"James E.J. Bottomley" <jejb@linux.vnet.ibm.com>,
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ejt@redhat.com, Kalle Valo <kvalo@codeaurora.org>,
Kees Cook <keescook@chromium.org>,
Larry Finger <Larry.Finger@lwfinger.net>,
Linus Walleij <linus.walleij@linaro.org>,
Madalin-Cristian Bucur <madalin.bucur@nxp.com>,
"Martin K. Petersen" <martin.petersen@oracle.com>,
Michael Ellerman <mpe@ellerman.id.au>,
"Michael S. Tsirkin" <mst@redhat.com>,
michal.kazior@tieto.com, Mike Snitzer <snitzer@redhat.com>,
Paul Burton <paul.burton@mips.com>,
Paul Mackerras <paulus@samba.org>,
"Rafael J. Wysocki" <rjw@rjwysocki.net>,
Ralf Baechle <ralf@linux-mips.org>,
Rob Clark <robdclark@gmail.com>,
rolandd@cisco.com, Salil Mehta <salil.mehta@huawei.com>,
Shuah Khan <shuah@kernel.org>,
srivatsa.bhat@linux.vnet.ibm.com, sviau@codeaurora.org,
Tejun Heo <tj@kernel.org>,
yisen.zhuang@huawei.com, zijun_hu@htc.com
Subject: Re: [PATCH 00/23] Make use of unlikely() more consistently.
Date: Fri, 31 Aug 2018 23:35:08 +0300 [thread overview]
Message-ID: <46369585-4d67-5235-d57d-a5162cc85e56@gmail.com> (raw)
In-Reply-To: <CAK8P3a2JasKXtXYoV7KsSZt4TwkffsBjrf=LK1HZJx0KFKCcow@mail.gmail.com>
On 31/08/18 17:09, Arnd Bergmann wrote:
[...]
>> #define assert(condition)
>> ...
>> if (unlikely(!(condition)))
>> error_action()
>> ...
>
> There is a potential that this introduces false-postive -Wmaybe-uninitialized
> warnings when CONFIG_PROFILE_ANNOTATED_BRANCHES is
> set, since that turns unlikely() into a complex operation that in turn
> confuses the compiler so it no longer keeps track of which variables
> are initialized or not.
>
> It's possible that none of your patches do that, but one needs to be aware
> of the problem, and possibly revert some of your patches if it does cause
> warning regressions in drivers that don't actually benefit from the
> micro-optimization.
I see.
But if such case might arise, it might be possible, instead of reverting
these patches, to locally - and conditionally - turn unlikely() into an
identity macro.
For example:
#ifdef CONFIG_PROFILE_ANNOTATOED_BRANCHES
#define unlikely(x) (x)
#endif
Without giving up the hint for the case of normal compilation.
--
igor
prev parent reply other threads:[~2018-08-31 20:35 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20180830223429.30051-1-igor.stoppa@huawei.com>
2018-08-30 22:34 ` [PATCH 01/23] infiniband: nes: add unlikely() to assert() Igor Stoppa
2018-08-31 14:06 ` Doug Ledford
2018-08-30 22:34 ` [PATCH 02/23] ethernet: hnae: " Igor Stoppa
2018-08-30 22:34 ` [PATCH 03/23] asm-generic: bug: add unlikely() to BUG_ON() Igor Stoppa
2018-08-30 22:34 ` [PATCH 04/23] mips: " Igor Stoppa
2018-08-30 22:34 ` [PATCH 05/23] selftest: vm: " Igor Stoppa
2018-08-30 22:57 ` Dmitry Safonov
2018-08-30 23:04 ` Dmitry Safonov
2018-08-31 21:25 ` Igor Stoppa
2018-08-30 22:34 ` [PATCH 06/23] virtio: add unlikely() to WARN_ON_ONCE() Igor Stoppa
2018-08-30 22:34 ` [PATCH 07/23] seccomp: remove unnecessary unlikely() Igor Stoppa
2018-09-02 21:26 ` Kees Cook
2018-08-30 22:34 ` [PATCH 08/23] drm: " Igor Stoppa
2018-08-30 22:34 ` [PATCH 09/23] cpufreq: " Igor Stoppa
2018-08-30 22:34 ` [PATCH 10/23] wireless: " Igor Stoppa
2018-08-31 9:52 ` Kalle Valo
2018-08-31 13:44 ` Igor Stoppa
2018-08-30 22:34 ` [PATCH 11/23] " Igor Stoppa
2018-08-30 22:34 ` [PATCH 12/23] " Igor Stoppa
2018-08-30 22:34 ` [PATCH 13/23] freescale: ethernet: " Igor Stoppa
2018-08-30 22:34 ` [PATCH 14/23] wimax: i2400m: " Igor Stoppa
2018-08-30 22:34 ` [PATCH 15/23] lvm: device mapper: " Igor Stoppa
2018-08-30 22:34 ` [PATCH 16/23] " Igor Stoppa
2018-08-30 22:34 ` [PATCH 17/23] usb: octeon-hcd: " Igor Stoppa
2018-08-30 22:34 ` [PATCH 18/23] infiniband: scsi: " Igor Stoppa
2018-08-30 22:53 ` Bart Van Assche
2018-08-30 22:34 ` [PATCH 19/23] pinctrl: " Igor Stoppa
2018-08-31 9:29 ` Linus Walleij
2018-08-30 22:34 ` [PATCH 20/23] mm: percpu: " Igor Stoppa
2018-08-31 1:58 ` Dennis Zhou
2018-08-30 22:34 ` [PATCH 21/23] filesystems: " Igor Stoppa
2018-08-30 22:34 ` [PATCH 22/23] powerpc: " Igor Stoppa
2018-08-30 22:34 ` [PATCH 23/23] scsi: " Igor Stoppa
2018-08-31 14:09 ` [PATCH 00/23] Make use of unlikely() more consistently Arnd Bergmann
2018-08-31 20:35 ` Igor Stoppa [this message]
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