From: Segher Boessenkool <segher@kernel.crashing.org>
To: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: linuxppc-dev@lists.ozlabs.org,
Michael Neuling <michael.neuling@au1.ibm.com>
Subject: Re: [PATCH] powerpc: Ensure gcc doesn't move around cache flushing in __patch_instruction
Date: Thu, 17 May 2018 14:23:31 -0500 [thread overview]
Message-ID: <20180517192331.GZ17342@gate.crashing.org> (raw)
In-Reply-To: <48284701fe497bb4f5bede5c55bbce9d70309562.camel@kernel.crashing.org>
Hi!
On Thu, May 17, 2018 at 01:06:10PM +1000, Benjamin Herrenschmidt wrote:
> The current asm statement in __patch_instruction() for the cache flushes
> doesn't have a "volatile" statement and no memory clobber. That means
> gcc can potentially move it around (or move the store done by put_user
> past the flush).
volatile is completely superfluous here, except maybe as documentation:
any asm without outputs is always volatile.
(And the memory clobber does not prevent the compiler from moving the
asm around, or duplicating it, etc., and neither does the volatile).
Segher
next prev parent reply other threads:[~2018-05-17 19:23 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-05-17 3:06 [PATCH] powerpc: Ensure gcc doesn't move around cache flushing in __patch_instruction Benjamin Herrenschmidt
2018-05-17 19:23 ` Segher Boessenkool [this message]
2018-05-17 22:30 ` Benjamin Herrenschmidt
2018-05-17 23:00 ` Segher Boessenkool
2019-01-31 13:20 ` Christophe Leroy
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20180517192331.GZ17342@gate.crashing.org \
--to=segher@kernel.crashing.org \
--cc=benh@kernel.crashing.org \
--cc=linuxppc-dev@lists.ozlabs.org \
--cc=michael.neuling@au1.ibm.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).