From: Vladimir Murzin <vladimir.murzin@arm.com>
To: Catalin Marinas <catalin.marinas@arm.com>,
Kenneth Lee <liguozhu@hisilicon.com>
Cc: Will Deacon <will.deacon@arm.com>,
linux-kernel@vger.kernel.org,
linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH] [bugfix] replace unnessary ldax with common ldr
Date: Wed, 31 Aug 2016 14:30:40 +0100 [thread overview]
Message-ID: <57C6DC00.2050709@arm.com> (raw)
In-Reply-To: <20160830090721.GC5163@e104818-lin.cambridge.arm.com>
On 30/08/16 10:07, Catalin Marinas wrote:
> On Tue, Aug 30, 2016 at 02:35:31PM +0800, Kenneth Lee wrote:
>> (add comment for the previous mail, sorry for the duplication)
>>
>> There is no store_ex pairing with this load_ex. It is not necessary and
>> gave wrong hint to the cache system.
>>
>> Signed-off-by: Kenneth Lee <liguozhu@hisilicon.com>
>> ---
>> arch/arm64/include/asm/spinlock.h | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/arch/arm64/include/asm/spinlock.h b/arch/arm64/include/asm/spinlock.h
>> index c85e96d..3334c4f 100644
>> --- a/arch/arm64/include/asm/spinlock.h
>> +++ b/arch/arm64/include/asm/spinlock.h
>> @@ -63,7 +63,7 @@ static inline void arch_spin_lock(arch_spinlock_t *lock)
>> */
>> " sevl\n"
>> "2: wfe\n"
>> -" ldaxrh %w2, %4\n"
>> +" ldrh %w2, %4\n"
>> " eor %w1, %w2, %w0, lsr #16\n"
>> " cbnz %w1, 2b\n"
>> /* We got the lock. Critical section starts here. */
>
> This is needed because the arch_spin_unlock() code only uses an STLR
> without an explicit SEV (like we have on AArch32). An event is
> automatically generated when the exclusive monitor is cleared by STLR.
> But without setting it with a load exclusive in arch_spin_lock() (even
> though it does not acquire the lock), there won't be anything to clear,
> hence no event to be generated. In this case, the WFE would wait
> indefinitely.
>
Maybe worth to add this as a comment, no?
Cheers
Vladimir
next prev parent reply other threads:[~2016-08-31 13:31 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-08-30 6:35 [PATCH] [bugfix] replace unnessary ldax with common ldr Kenneth Lee
2016-08-30 9:07 ` Catalin Marinas
2016-08-31 13:30 ` Vladimir Murzin [this message]
2016-09-01 10:20 ` Catalin Marinas
-- strict thread matches above, loose matches on Subject: below --
2016-08-30 4:13 Kenneth Lee
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=57C6DC00.2050709@arm.com \
--to=vladimir.murzin@arm.com \
--cc=catalin.marinas@arm.com \
--cc=liguozhu@hisilicon.com \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=linux-kernel@vger.kernel.org \
--cc=will.deacon@arm.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