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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
op-state-get.c 
/*
 * Linux WiMAX
 * Implement and export a method for getting a WiMAX device current state
 *
 * Copyright (C) 2009 Paulius Zaleckas <paulius.zaleckas@teltonika.lt>
 *
 * Based on previous WiMAX core work by:
 *  Copyright (C) 2008 Intel Corporation <linux-wimax@intel.com>
 *  Inaky Perez-Gonzalez <inaky.perez-gonzalez@intel.com>
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License version
 * 2 as published by the Free Software Foundation.
 *
 * 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., 51 Franklin Street, Fifth Floor, Boston, MA
 * 02110-1301, USA.
 */

#include <net/wimax.h>
#include <net/genetlink.h>
#include <linux/wimax.h>
#include <linux/security.h>
#include "wimax-internal.h"

#define D_SUBMODULE op_state_get
#include "debug-levels.h"


/*
 * Exporting to user space over generic netlink
 *
 * Parse the state get command from user space, return a combination
 * value that describe the current state.
 *
 * No attributes.
 */
int wimax_gnl_doit_state_get(struct sk_buff *skb, struct genl_info *info)
{
	int result, ifindex;
	struct wimax_dev *wimax_dev;

	d_fnstart(3, NULL, "(skb %p info %p)\n", skb, info);
	result = -ENODEV;
	if (info->attrs[WIMAX_GNL_STGET_IFIDX] == NULL) {
		pr_err("WIMAX_GNL_OP_STATE_GET: can't find IFIDX attribute\n");
		goto error_no_wimax_dev;
	}
	ifindex = nla_get_u32(info->attrs[WIMAX_GNL_STGET_IFIDX]);
	wimax_dev = wimax_dev_get_by_genl_info(info, ifindex);
	if (wimax_dev == NULL)
		goto error_no_wimax_dev;
	/* Execute the operation and send the result back to user space */
	result = wimax_state_get(wimax_dev);
	dev_put(wimax_dev->net_dev);
error_no_wimax_dev:
	d_fnend(3, NULL, "(skb %p info %p) = %d\n", skb, info, result);
	return result;
}
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