From: Chris Metcalf <cmetcalf@mellanox.com>
To: Arnd Bergmann <arnd@arndb.de>
Cc: Martin Jambor <mjambor@suse.cz>,
"Martin K. Petersen" <martin.petersen@oracle.com>,
James Bottomley <James.Bottomley@hansenpartnership.com>,
Josh Poimboeuf <jpoimboe@redhat.com>,
<linux-scsi@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
Denys Vlasenko <dvlasenk@redhat.com>, Thomas Graf <tgraf@suug.ch>,
Peter Zijlstra <peterz@infradead.org>,
David Rientjes <rientjes@google.com>,
Andrew Morton <akpm@linux-foundation.org>,
Ingo Molnar <mingo@kernel.org>,
Himanshu Madhani <himanshu.madhani@qlogic.com>,
<qla2xxx-upstream@qlogic.com>, Jan Hubicka <hubicka@ucw.cz>
Subject: Re: [PATCH] scsi: fc: force inlining of wwn conversion functions
Date: Thu, 28 Apr 2016 11:48:57 -0400 [thread overview]
Message-ID: <744a7126-47f7-c325-b208-cab8c30bcc0d@mellanox.com> (raw)
In-Reply-To: <2544325.pieyAoijz1@wuerfel>
On 4/28/2016 11:23 AM, Arnd Bergmann wrote:
> On Thursday 28 April 2016 10:58:43 Chris Metcalf wrote:
>> (Resending as text/plain)
>>
>> On 4/27/2016 5:34 PM, Arnd Bergmann wrote:
>>> This won't help on TILE, which is the one architecture that sets
>>> ARCH_SUPPORTS_OPTIMIZED_INLINING but does not set ARCH_USE_BUILTIN_BSWAP.
>>> Chris Metcalf should be able to figure out whether we can just
>>> set ARCH_USE_BUILTIN_BSWAP for tile as well.
>> We certainly could enable ARCH_USE_BUILTIN_BSWAP. The only problem is
>> that we never added explicit support for bswap16() in gcc, which is
>> efficiently done on tilegx via the "revbytes" instruction and a 48-bit
>> right-shift. So gcc instead does a generic thing with four
>> instructions in three bundles, so really not as good as our asm/swab.h.
>>
>> I'm not sure how to weigh the implications of converting to
>> builtin_bswap16 (and possibly upstreaming a better implementation to
>> gcc), vs. disabling ARCH_SUPPORTS_OPTIMIZED_INLINING (which no one
>> else but x86 uses anyway), vs. just ignoring the compiler bug and
>> hoping it's not an issue in practice
> How about figuring out whether you hit the gcc bug on tile as a
> first step?
I don't have an affected build of gcc handy (just 4.8 and 4.4). I will pass
this to our compiler folks and see what they know.
> Another idea would be to adapt this section in include/linux/compiler-gcc.h:
>
> #if !defined(CONFIG_ARCH_SUPPORTS_OPTIMIZED_INLINING) || \
> !defined(CONFIG_OPTIMIZE_INLINING) || (__GNUC__ < 4)
> #define inline inline __attribute__((always_inline)) notrace
> #define __inline__ __inline__ __attribute__((always_inline)) notrace
> #define __inline __inline __attribute__((always_inline)) notrace
> #else
> /* A lot of inline functions can cause havoc with function tracing */
> #define inline inline notrace
> #define __inline__ __inline__ notrace
> #define __inline __inline notrace
> #endif
>
> to work around the issue. We already check for gcc before 4.0, and
> we could also check for the affected releases (4.9, 5.x, 6.1) in the
> same place, possibly conditional on ARCH_USE_BUILTIN_BSWAP with
> a comment pointing to the gcc bug tracker.
This does seem like a more robust solution anyway, since more instances of the
bad inline pattern might get introduced in the future in other places.
I wouldn't make it conditional on ARCH_USE_BUILTIN_BSWAP for the same reason.
--
Chris Metcalf, Mellanox Technologies
http://www.mellanox.com
next prev parent reply other threads:[~2016-04-28 15:49 UTC|newest]
Thread overview: 45+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-02-04 19:45 [PATCH] asm-generic: force inlining of some atomic_long operations Denys Vlasenko
2016-02-04 19:45 ` [PATCH] force inlining of some byteswap operations Denys Vlasenko
2016-02-05 7:28 ` Ingo Molnar
2016-04-13 3:36 ` This patch triggers a bad gcc bug (was Re: [PATCH] force inlining of some byteswap operations) Josh Poimboeuf
2016-04-13 12:12 ` Denys Vlasenko
2016-04-13 12:36 ` Josh Poimboeuf
2016-04-13 15:15 ` Josh Poimboeuf
2016-04-13 16:55 ` James Bottomley
2016-04-13 17:10 ` Josh Poimboeuf
2016-04-14 15:29 ` Denys Vlasenko
2016-04-14 15:57 ` Josh Poimboeuf
2016-04-14 17:09 ` Denys Vlasenko
2016-04-15 5:45 ` Ingo Molnar
2016-04-15 13:47 ` Josh Poimboeuf
2016-04-15 22:20 ` Josh Poimboeuf
2016-04-16 9:03 ` Ingo Molnar
2016-04-18 13:39 ` Josh Poimboeuf
2016-04-18 14:07 ` Arnd Bergmann
2016-04-18 14:12 ` Josh Poimboeuf
2016-04-18 14:21 ` Arnd Bergmann
2016-04-19 8:52 ` Ingo Molnar
2016-04-19 13:56 ` [PATCH] scsi: fc: force inlining of wwn conversion functions Josh Poimboeuf
2016-04-22 23:17 ` Quinn Tran
2016-04-25 16:07 ` Josh Poimboeuf
2016-04-26 2:40 ` Martin K. Petersen
2016-04-26 3:37 ` James Bottomley
2016-04-26 7:22 ` Arnd Bergmann
2016-04-26 8:35 ` Christoph Hellwig
2016-04-26 10:05 ` Arnd Bergmann
2016-04-26 13:06 ` Martin K. Petersen
2016-04-26 15:58 ` Arnd Bergmann
2016-04-26 22:36 ` James Bottomley
2016-04-27 0:44 ` Martin K. Petersen
2016-04-27 11:05 ` Martin Jambor
2016-04-27 21:34 ` Arnd Bergmann
2016-04-28 14:58 ` Chris Metcalf
2016-04-28 15:23 ` Arnd Bergmann
2016-04-28 15:48 ` Chris Metcalf [this message]
2016-04-27 22:00 ` [PATCH, RFT] byteswap: try to avoid __builtin_constant_p gcc bug Arnd Bergmann
2016-04-27 22:11 ` Josh Poimboeuf
2016-04-28 16:27 ` Quinn Tran
2016-04-16 7:42 ` This patch triggers a bad gcc bug (was Re: [PATCH] force inlining of some byteswap operations) Arnd Bergmann
2016-04-18 13:22 ` Josh Poimboeuf
2016-02-04 19:45 ` [PATCH] force inlining of unaligned byteswap operations Denys Vlasenko
2016-02-05 7:28 ` Ingo Molnar
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=744a7126-47f7-c325-b208-cab8c30bcc0d@mellanox.com \
--to=cmetcalf@mellanox.com \
--cc=James.Bottomley@hansenpartnership.com \
--cc=akpm@linux-foundation.org \
--cc=arnd@arndb.de \
--cc=dvlasenk@redhat.com \
--cc=himanshu.madhani@qlogic.com \
--cc=hubicka@ucw.cz \
--cc=jpoimboe@redhat.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-scsi@vger.kernel.org \
--cc=martin.petersen@oracle.com \
--cc=mingo@kernel.org \
--cc=mjambor@suse.cz \
--cc=peterz@infradead.org \
--cc=qla2xxx-upstream@qlogic.com \
--cc=rientjes@google.com \
--cc=tgraf@suug.ch \
/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 read-only IMAP folder(s) and NNTP newsgroup(s).