From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: "Desai, Kashyap" <Kashyap.Desai@lsi.com>
Cc: James Bottomley <James.Bottomley@HansenPartnership.com>,
"Moore, Eric" <Eric.Moore@lsi.com>,
"linux-scsi@vger.kernel.org" <linux-scsi@vger.kernel.org>,
"Prakash, Sathya" <Sathya.Prakash@lsi.com>,
paulus@samba.org, linuxppc-dev@lists.ozlabs.org,
Matthew Wilcox <matthew@wil.cx>
Subject: Re: [PATCH 1/3] mpt2sas: remove the use of writeq, since writeq is not atomic
Date: Wed, 18 May 2011 15:45:43 +1000 [thread overview]
Message-ID: <1305697543.2781.28.camel@pasglop> (raw)
In-Reply-To: <20110518041551.GL15227@parisc-linux.org>
> > > Cc: stable@kernle.org
> > > Signed-off-by: Kashyap Desai <kashyap.desai@lsi.com>
> > > ---
> > > diff --git a/drivers/scsi/mpt2sas/mpt2sas_base.c b/drivers/scsi/mpt2sas/mpt2sas_base.c
> > > index efa0255..5778334 100644
> > > --- a/drivers/scsi/mpt2sas/mpt2sas_base.c
> > > +++ b/drivers/scsi/mpt2sas/mpt2sas_base.c
> > > @@ -1558,7 +1558,6 @@ mpt2sas_base_free_smid(struct MPT2SAS_ADAPTER *ioc, u16 smid)
> > > * care of 32 bit environment where its not quarenteed to send the entire word
> > > * in one transfer.
> > > */
> > > -#ifndef writeq
> >
> > Why not make this #ifndef CONFIG_64BIT? You know that all 64 bit
> > systems have writeq implemented correctly; you suspect 32 bit systems
> > don't.
> >
> > James
> >
> > James, This issue was observed on PPC64 system. So what you have
> suggested will not solve this issue.
> > If we are sure that writeq() is atomic across all architecture, we
> can use it safely. As we have seen issue on ppc64, we are not
> confident to use
> > "writeq" call.
>
> So have you told the powerpc people that they have a broken writeq?
> And why do you obfuscate your report by talking about i386 when it's
> really about powerpc64?
Well, our writeq isn't supposed to be broken :-)
It's defined as an std instruction (and "ld" for readq) so that's
perfectly atomic ... provided your access is aligned. Is it ?
Cheers,
Be
WARNING: multiple messages have this Message-ID (diff)
From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: "Desai, Kashyap" <Kashyap.Desai@lsi.com>
Cc: "Prakash, Sathya" <Sathya.Prakash@lsi.com>,
"linux-scsi@vger.kernel.org" <linux-scsi@vger.kernel.org>,
Matthew Wilcox <matthew@wil.cx>,
linuxppc-dev@lists.ozlabs.org,
James Bottomley <James.Bottomley@HansenPartnership.com>,
paulus@samba.org, "Moore, Eric" <Eric.Moore@lsi.com>
Subject: Re: [PATCH 1/3] mpt2sas: remove the use of writeq, since writeq is not atomic
Date: Wed, 18 May 2011 15:45:43 +1000 [thread overview]
Message-ID: <1305697543.2781.28.camel@pasglop> (raw)
In-Reply-To: <20110518041551.GL15227@parisc-linux.org>
> > > Cc: stable@kernle.org
> > > Signed-off-by: Kashyap Desai <kashyap.desai@lsi.com>
> > > ---
> > > diff --git a/drivers/scsi/mpt2sas/mpt2sas_base.c b/drivers/scsi/mpt2sas/mpt2sas_base.c
> > > index efa0255..5778334 100644
> > > --- a/drivers/scsi/mpt2sas/mpt2sas_base.c
> > > +++ b/drivers/scsi/mpt2sas/mpt2sas_base.c
> > > @@ -1558,7 +1558,6 @@ mpt2sas_base_free_smid(struct MPT2SAS_ADAPTER *ioc, u16 smid)
> > > * care of 32 bit environment where its not quarenteed to send the entire word
> > > * in one transfer.
> > > */
> > > -#ifndef writeq
> >
> > Why not make this #ifndef CONFIG_64BIT? You know that all 64 bit
> > systems have writeq implemented correctly; you suspect 32 bit systems
> > don't.
> >
> > James
> >
> > James, This issue was observed on PPC64 system. So what you have
> suggested will not solve this issue.
> > If we are sure that writeq() is atomic across all architecture, we
> can use it safely. As we have seen issue on ppc64, we are not
> confident to use
> > "writeq" call.
>
> So have you told the powerpc people that they have a broken writeq?
> And why do you obfuscate your report by talking about i386 when it's
> really about powerpc64?
Well, our writeq isn't supposed to be broken :-)
It's defined as an std instruction (and "ld" for readq) so that's
perfectly atomic ... provided your access is aligned. Is it ?
Cheers,
Be
next prev parent reply other threads:[~2011-05-18 5:46 UTC|newest]
Thread overview: 46+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-05-04 11:53 [PATCH 1/3] mpt2sas: remove the use of writeq, since writeq is not atomic Kashyap, Desai
2011-05-17 7:16 ` James Bottomley
2011-05-18 4:07 ` Desai, Kashyap
2011-05-18 4:15 ` Matthew Wilcox
2011-05-18 4:15 ` Matthew Wilcox
2011-05-18 4:23 ` James Bottomley
2011-05-18 4:23 ` James Bottomley
2011-05-18 7:00 ` Benjamin Herrenschmidt
2011-05-18 7:00 ` Benjamin Herrenschmidt
2011-05-18 8:23 ` Milton Miller
2011-05-18 8:23 ` Milton Miller
2011-05-18 15:35 ` Moore, Eric
2011-05-18 15:35 ` Moore, Eric
2011-05-18 18:31 ` Milton Miller
2011-05-18 18:31 ` Milton Miller
2011-05-18 18:31 ` Milton Miller
2011-05-18 19:11 ` Moore, Eric
2011-05-18 19:11 ` Moore, Eric
2011-05-18 19:11 ` Moore, Eric
2011-05-19 4:08 ` Hitoshi Mitake
2011-05-19 4:08 ` Hitoshi Mitake
2011-05-19 4:46 ` James Bottomley
2011-05-19 4:46 ` James Bottomley
2011-05-19 5:36 ` Benjamin Herrenschmidt
2011-05-19 5:36 ` Benjamin Herrenschmidt
2011-05-19 8:35 ` [PATCH 1/3] mpt2sas: remove the use of writeq, since writeq isnot atomic David Laight
2011-05-19 8:35 ` David Laight
2011-05-19 8:35 ` David Laight
2011-05-19 4:16 ` [PATCH 1/3] mpt2sas: remove the use of writeq, since writeq is not atomic Roland Dreier
2011-05-19 4:16 ` Roland Dreier
2011-05-19 5:34 ` Benjamin Herrenschmidt
2011-05-19 5:34 ` Benjamin Herrenschmidt
2011-05-19 18:15 ` Ingo Molnar
2011-05-19 18:15 ` Ingo Molnar
2011-05-19 23:54 ` [PATCH] x86: Remove 32-bit versions of readq()/writeq() Roland Dreier
2011-05-20 1:15 ` Hitoshi Mitake
2011-05-20 8:05 ` Desai, Kashyap
2011-05-20 11:44 ` Ingo Molnar
2011-05-20 12:03 ` James Bottomley
2011-05-18 21:30 ` [PATCH 1/3] mpt2sas: remove the use of writeq, since writeq is not atomic Benjamin Herrenschmidt
2011-05-18 22:05 ` Moore, Eric
2011-05-18 22:05 ` Moore, Eric
2011-05-18 8:04 ` [PATCH 1/3] mpt2sas: remove the use of writeq, since writeq isnot atomic David Laight
2011-05-18 8:04 ` David Laight
2011-05-18 5:45 ` Benjamin Herrenschmidt [this message]
2011-05-18 5:45 ` [PATCH 1/3] mpt2sas: remove the use of writeq, since writeq is not atomic Benjamin Herrenschmidt
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