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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
debug-levels.h 
/*
 * Linux WiMAX Stack
 * Debug levels control file for the wimax module
 *
 *
 * Copyright (C) 2007-2008 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.
 */
#ifndef __debug_levels__h__
#define __debug_levels__h__

/* Maximum compile and run time debug level for all submodules */
#define D_MODULENAME wimax
#define D_MASTER CONFIG_WIMAX_DEBUG_LEVEL

#include <linux/wimax/debug.h>

/* List of all the enabled modules */
enum d_module {
	D_SUBMODULE_DECLARE(debugfs),
	D_SUBMODULE_DECLARE(id_table),
	D_SUBMODULE_DECLARE(op_msg),
	D_SUBMODULE_DECLARE(op_reset),
	D_SUBMODULE_DECLARE(op_rfkill),
	D_SUBMODULE_DECLARE(op_state_get),
	D_SUBMODULE_DECLARE(stack),
};

#endif /* #ifndef __debug_levels__h__ */
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