From: "Srivatsa S. Bhat" <srivatsa.bhat@linux.vnet.ibm.com>
To: Chuansheng Liu <chuansheng.liu@intel.com>
Cc: tglx@linutronix.de, mingo@redhat.com, x86@kernel.org,
linux-kernel@vger.kernel.org, yanmin_zhang@linux.intel.com
Subject: Re: [PATCH RESEND] x86/fixup_irq: Clean the offlining CPU from the irq affinity mask
Date: Wed, 26 Sep 2012 14:19:07 +0530 [thread overview]
Message-ID: <5062C183.20301@linux.vnet.ibm.com> (raw)
In-Reply-To: <1348681092.19514.10.camel@cliu38-desktop-build>
On 09/26/2012 11:08 PM, Chuansheng Liu wrote:
>
> When one CPU is going offline, and fixup_irqs() will re-set the
> irq affinity in some cases, we should clean the offlining CPU from
> the irq affinity.
>
> The reason is setting offlining CPU as of the affinity is useless.
> Moreover, the smp_affinity value will be confusing when the
> offlining CPU come back again.
>
> Example:
> For irq 93 with 4 CPUS, the default affinity f(1111),
> normal cases: 4 CPUS will receive the irq93 interrupts.
>
> When echo 0 > /sys/devices/system/cpu/cpu3/online, just CPU0,1,2 will
> receive the interrupts.
>
> But after the CPU3 is online again, we will not set affinity,the result
> will be:
> the smp_affinity is f, but still just CPU0,1,2 can receive the interrupts.
>
> So we should clean the offlining CPU from irq affinity mask
> in fixup_irqs().
>
> Reviewed-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Please hold on.. I'm not yet done reviewing, I might have more comments :-)
> Signed-off-by: liu chuansheng <chuansheng.liu@intel.com>
> ---
> arch/x86/kernel/irq.c | 8 ++++++--
> 1 files changed, 6 insertions(+), 2 deletions(-)
>
> diff --git a/arch/x86/kernel/irq.c b/arch/x86/kernel/irq.c
> index d44f782..08bb905 100644
> --- a/arch/x86/kernel/irq.c
> +++ b/arch/x86/kernel/irq.c
> @@ -239,6 +239,7 @@ void fixup_irqs(void)
> struct irq_desc *desc;
> struct irq_data *data;
> struct irq_chip *chip;
> + int cpu = smp_processor_id();
>
> for_each_irq_desc(irq, desc) {
> int break_affinity = 0;
> @@ -277,8 +278,11 @@ void fixup_irqs(void)
> if (!irqd_can_move_in_process_context(data) && chip->irq_mask)
> chip->irq_mask(data);
>
> - if (chip->irq_set_affinity)
> - chip->irq_set_affinity(data, affinity, true);
> + if ((chip->irq_set_affinity) &&
> + !chip->irq_set_affinity(data, affinity, true)) {
A return value of 0 and 1 are acceptable. So this check isn't correct.
Regards,
Srivatsa S. Bhat
> + if (cpumask_test_cpu(cpu, data->affinity))
> + cpumask_clear_cpu(cpu, data->affinity);
OMG, why did you drop the other hunk which cleared the cpu *before*
invoking ->irq_set_affinity()? IMO, altering irq affinity involves more work
than just altering the mask; that's why you have that ->irq_set_affinity()
function. So, if you alter the mask *after* calling ->irq_set_affinity(),
its not right..
Regards,
Srivatsa S. Bhat
> + }
> else if (!(warned++))
> set_affinity = 0;
>
next prev parent reply other threads:[~2012-09-26 8:49 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-09-26 17:38 [PATCH RESEND] x86/fixup_irq: Clean the offlining CPU from the irq affinity mask Chuansheng Liu
2012-09-26 8:49 ` Srivatsa S. Bhat [this message]
2012-09-26 8:51 ` Liu, Chuansheng
2012-09-26 8:56 ` Liu, Chuansheng
2012-09-26 9:02 ` Srivatsa S. Bhat
2012-09-26 23:45 ` Chuansheng Liu
2012-09-26 15:47 ` Srivatsa S. Bhat
2012-09-26 16:03 ` Srivatsa S. Bhat
2012-09-26 17:06 ` Suresh Siddha
2012-09-26 17:30 ` Srivatsa S. Bhat
2012-09-26 22:46 ` Suresh Siddha
2012-09-27 18:42 ` Srivatsa S. Bhat
2012-09-27 19:20 ` Suresh Siddha
2012-09-27 20:33 ` Srivatsa S. Bhat
2012-10-09 8:51 ` Liu, Chuansheng
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=5062C183.20301@linux.vnet.ibm.com \
--to=srivatsa.bhat@linux.vnet.ibm.com \
--cc=chuansheng.liu@intel.com \
--cc=linux-kernel@vger.kernel.org \
--cc=mingo@redhat.com \
--cc=tglx@linutronix.de \
--cc=x86@kernel.org \
--cc=yanmin_zhang@linux.intel.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).