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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
netevent.c 
/*
 *	Network event notifiers
 *
 *	Authors:
 *      Tom Tucker             <tom@opengridcomputing.com>
 *      Steve Wise             <swise@opengridcomputing.com>
 *
 *	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.
 *
 *	Fixes:
 */

#include <linux/rtnetlink.h>
#include <linux/notifier.h>
#include <linux/export.h>
#include <net/netevent.h>

static ATOMIC_NOTIFIER_HEAD(netevent_notif_chain);

/**
 *	register_netevent_notifier - register a netevent notifier block
 *	@nb: notifier
 *
 *	Register a notifier to be called when a netevent occurs.
 *	The notifier passed is linked into the kernel structures and must
 *	not be reused until it has been unregistered. A negative errno code
 *	is returned on a failure.
 */
int register_netevent_notifier(struct notifier_block *nb)
{
	return atomic_notifier_chain_register(&netevent_notif_chain, nb);
}
EXPORT_SYMBOL_GPL(register_netevent_notifier);

/**
 *	netevent_unregister_notifier - unregister a netevent notifier block
 *	@nb: notifier
 *
 *	Unregister a notifier previously registered by
 *	register_neigh_notifier(). The notifier is unlinked into the
 *	kernel structures and may then be reused. A negative errno code
 *	is returned on a failure.
 */

int unregister_netevent_notifier(struct notifier_block *nb)
{
	return atomic_notifier_chain_unregister(&netevent_notif_chain, nb);
}
EXPORT_SYMBOL_GPL(unregister_netevent_notifier);

/**
 *	call_netevent_notifiers - call all netevent notifier blocks
 *      @val: value passed unmodified to notifier function
 *      @v:   pointer passed unmodified to notifier function
 *
 *	Call all neighbour notifier blocks.  Parameters and return value
 *	are as for notifier_call_chain().
 */

int call_netevent_notifiers(unsigned long val, void *v)
{
	return atomic_notifier_call_chain(&netevent_notif_chain, val, v);
}
EXPORT_SYMBOL_GPL(call_netevent_notifiers);
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