From: James Bottomley <James.Bottomley@HansenPartnership.com>
To: Andy Lutomirski <luto@amacapital.net>
Cc: Kashyap Desai <kashyap.desai@avagotech.com>,
Sumit Saxena <sumit.saxena@avagotech.com>,
Uday Lingala <uday.lingala@avagotech.com>,
megaraidlinux.pdl@avagotech.com,
Linux SCSI List <linux-scsi@vger.kernel.org>
Subject: Re: smp_processor_id warning in megasas driver on 3.19.3
Date: Wed, 08 Apr 2015 11:17:49 -0700 [thread overview]
Message-ID: <1428517069.2224.36.camel@HansenPartnership.com> (raw)
In-Reply-To: <CALCETrXUZ=qbQmaEdiKAn+HgU7Vmx3arwGF_zyYJwTShqGcx_A@mail.gmail.com>
On Wed, 2015-04-08 at 10:59 -0700, Andy Lutomirski wrote:
> This is a regression somewhere between 3.15 and 3.19.3. Let me know
> if more diagnostics would be helpful.
It's not a regression. Likely someone turned on additional warnings.
So the problem is that the warning is incorrect: the use of
smp_processor_id() isn't pre-empt unsafe. The driver is using it as a
hint as to which queue it should be using, so it doesn't matter if
pre-empt schedules the driver thread away from that CPU.
I presume the warning is because whoever added it thinks that you should
be using the get/put cpu API, which would be wholly inappropriate here
because we don't want to bind the thread, we just want a hint about the
queue.
James
next prev parent reply other threads:[~2015-04-08 18:17 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-04-08 17:59 smp_processor_id warning in megasas driver on 3.19.3 Andy Lutomirski
2015-04-08 18:17 ` James Bottomley [this message]
2015-04-08 18:26 ` Andy Lutomirski
2015-04-08 18:29 ` James Bottomley
2015-04-08 18:55 ` Elliott, Robert (Server Storage)
2015-04-08 18:51 ` Christoph Hellwig
2015-04-08 19:14 ` Andy Lutomirski
2015-04-15 16:09 ` Sumit Saxena
2015-04-15 16:44 ` [PATCH] megaraid_sas: use raw_smp_processor_id() Christoph Hellwig
2015-04-15 20:22 ` Andy Lutomirski
2015-04-21 10:15 ` Hannes Reinecke
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