From: Lu Baolu <baolu.lu@linux.intel.com>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Mathias Nyman <mathias.nyman@linux.intel.com>,
Ingo Molnar <mingo@redhat.com>,
linux-usb@vger.kernel.org, x86@kernel.org,
LKML <linux-kernel@vger.kernel.org>,
Peter Zijlstra <peterz@infradead.org>
Subject: Re: [PATCH v4 1/4] usb: dbc: early driver for xhci debug capability
Date: Fri, 11 Nov 2016 10:49:04 +0800 [thread overview]
Message-ID: <582531A0.1080703@linux.intel.com> (raw)
In-Reply-To: <58252BDB.1020005@linux.intel.com>
Hi,
On 11/11/2016 10:24 AM, Lu Baolu wrote:
>> The only thing you can do to make this work is to prevent printing in NMI
>> > context:
>> >
>> > write()
>> > {
>> > if (in_nmi())
>> > return;
>> >
>> > raw_spinlock_irqsave(&lock, flags);
>> > ....
>> >
>> > That fully serializes the writes and just ignores NMI context printks. Not
>> > optimal, but I fear that's all you can do.
> Yes. But I want to add a bit more.
>
> write()
> {
> if (in_nmi() && raw_spin_is_locked(&lock)) {
> trace("... ...");
> return;
> }
>
> raw_spinlock_irqsave(&lock, flags);
> ....
Or...?
write()
{
if (in_nmi() && raw_spin_is_locked(&lock)) {
save_nmi_message_in_local_buf();
set_nmi_message_pending_flag();
return;
}
if (nmi_message_pending_flag_is_set()) {
write_nmi_message();
clear_nmi_message_pending_flag();
}
raw_spinlock_irqsave(&lock, flags);
....
Best regards,
Lu Baolu
next prev parent reply other threads:[~2016-11-11 2:49 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-11-01 4:59 [PATCH v4 0/4] usb: early: add support for early printk through USB3 debug port Lu Baolu
2016-11-01 4:59 ` [PATCH v4 1/4] usb: dbc: early driver for xhci debug capability Lu Baolu
2016-11-09 9:23 ` Thomas Gleixner
2016-11-10 1:13 ` Lu Baolu
2016-11-09 9:37 ` Thomas Gleixner
2016-11-10 1:20 ` Lu Baolu
2016-11-10 8:56 ` Thomas Gleixner
2016-11-10 11:44 ` Peter Zijlstra
2016-11-11 4:33 ` Lu Baolu
2016-11-11 12:28 ` Peter Zijlstra
2016-11-12 7:35 ` Lu Baolu
2016-11-12 11:32 ` Thomas Gleixner
2016-11-11 2:24 ` Lu Baolu
2016-11-11 2:49 ` Lu Baolu [this message]
2016-11-01 4:59 ` [PATCH v4 2/4] x86: add support for earlyprintk via USB3 debug port Lu Baolu
2016-11-01 4:59 ` [PATCH v4 3/4] usb: serial: usb_debug: add support for dbc debug device Lu Baolu
2016-11-01 4:59 ` [PATCH v4 4/4] usb: doc: add document for USB3 debug port usage Lu Baolu
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