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Revision bb143f814ea488769ca2e79e0b376139cb5f134b authored by Vineet Gupta on 23 February 2016, 06:25:16 UTC, committed by Vineet Gupta on 24 February 2016, 05:37:28 UTC 
ARCv2: SMP: Emulate IPI to self using software triggered interrupt
 
ARConnect/MCIP Inter-Core-Interrupt module can't send interrupt to
local core. So use core intc capability to trigger software
interrupt to self, using an unsued IRQ #21.

This showed up as csd deadlock with LTP trace_sched on a dual core
system. This test acts as scheduler fuzzer, triggering all sorts of
schedulting activity. Trouble starts with IPI to self, which doesn't get
delivered (effectively lost due to H/w capability), but the msg intended
to be sent remain enqueued in per-cpu @ipi_data.

All subsequent IPIs to this core from other cores get elided due to the
IPI coalescing optimization in ipi_send_msg_one() where a pending msg
implies an IPI already sent and assumes other core is yet to ack it.
After the elided IPI, other core simply goes into csd_lock_wait()
but never comes out as this core never sees the interrupt.

Fixes STAR 9001008624

Cc: Peter Zijlstra <peterz@infradead.org>
Cc: <stable@vger.kernel.org>        [4.2]
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
1 parent 3e5177c
Raw File
timestamping.c 
/*
 * PTP 1588 clock support - support for timestamping in PHY devices
 *
 * Copyright (C) 2010 OMICRON electronics GmbH
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation; either version 2 of the License, or
 *  (at your option) any later version.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program; if not, write to the Free Software
 *  Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */
#include <linux/errqueue.h>
#include <linux/phy.h>
#include <linux/ptp_classify.h>
#include <linux/skbuff.h>
#include <linux/export.h>

static unsigned int classify(const struct sk_buff *skb)
{
	if (likely(skb->dev && skb->dev->phydev &&
		   skb->dev->phydev->drv))
		return ptp_classify_raw(skb);
	else
		return PTP_CLASS_NONE;
}

void skb_clone_tx_timestamp(struct sk_buff *skb)
{
	struct phy_device *phydev;
	struct sk_buff *clone;
	unsigned int type;

	if (!skb->sk)
		return;

	type = classify(skb);
	if (type == PTP_CLASS_NONE)
		return;

	phydev = skb->dev->phydev;
	if (likely(phydev->drv->txtstamp)) {
		clone = skb_clone_sk(skb);
		if (!clone)
			return;
		phydev->drv->txtstamp(phydev, clone, type);
	}
}
EXPORT_SYMBOL_GPL(skb_clone_tx_timestamp);

bool skb_defer_rx_timestamp(struct sk_buff *skb)
{
	struct phy_device *phydev;
	unsigned int type;

	if (!skb->dev || !skb->dev->phydev || !skb->dev->phydev->drv)
		return false;

	if (skb_headroom(skb) < ETH_HLEN)
		return false;

	__skb_push(skb, ETH_HLEN);

	type = ptp_classify_raw(skb);

	__skb_pull(skb, ETH_HLEN);

	if (type == PTP_CLASS_NONE)
		return false;

	phydev = skb->dev->phydev;
	if (likely(phydev->drv->rxtstamp))
		return phydev->drv->rxtstamp(phydev, skb, type);

	return false;
}
EXPORT_SYMBOL_GPL(skb_defer_rx_timestamp);
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