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: Thu, 10 Nov 2016 09:20:35 +0800 [thread overview]
Message-ID: <5823CB63.7090603@linux.intel.com> (raw)
In-Reply-To: <alpine.DEB.2.20.1611091030171.3501@nanos>
Hi,
On 11/09/2016 05:37 PM, Thomas Gleixner wrote:
> On Tue, 1 Nov 2016, Lu Baolu wrote:
>> +static void early_xdbc_write(struct console *con, const char *str, u32 n)
>> +{
>> + int chunk, ret;
>> + static char buf[XDBC_MAX_PACKET];
>> + int use_cr = 0;
>> +
>> + if (!xdbc.xdbc_reg)
>> + return;
>> + memset(buf, 0, XDBC_MAX_PACKET);
> How is that dealing with reentrancy?
>
> early_printk() does not protect against it. Peter has a patch to prevent
> concurrent access from different cpus, but it cannot and will never prevent
> reentrancy on the same cpu (interrupt, nmi).
I can use a spinlock_irq to protect reentrancy of interrupt on the same
cpu. But I have no idea about the nmi one. This seems to be a common
issue for all early printk drivers.
Peter, any idea?
Best regards,
Lu Baolu
next prev parent reply other threads:[~2016-11-10 1:20 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 [this message]
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
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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