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From: Thomas Gleixner <tglx@linutronix.de>
To: Lu Baolu <baolu.lu@linux.intel.com>
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: Wed, 9 Nov 2016 10:37:11 +0100 (CET)	[thread overview]
Message-ID: <alpine.DEB.2.20.1611091030171.3501@nanos> (raw)
In-Reply-To: <1477976354-13291-2-git-send-email-baolu.lu@linux.intel.com>

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).

Thanks,

	tglx

  parent reply	other threads:[~2016-11-09  9:39 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 [this message]
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
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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