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05 April 2024, 19:05:47 UTC
Revision 207ee84133c00a8a2a5bdec94df4a5b37d78881c authored by Mike Christie on 02 March 2017, 05:13:26 UTC, committed by Nicholas Bellinger on 18 March 2017, 21:47:27 UTC 
target: Use system workqueue for ALUA transitions
 
If tcmu-runner is processing a STPG and needs to change the kernel's
ALUA state then we cannot use the same work queue for task management
requests and ALUA transitions, because we could deadlock. The problem
occurs when a STPG times out before tcmu-runner is able to
call into target_tg_pt_gp_alua_access_state_store->
core_alua_do_port_transition -> core_alua_do_transition_tg_pt ->
queue_work. In this case, the tmr is on the work queue waiting for
the STPG to complete, but the STPG transition is now queued behind
the waiting tmr.

Note:
This bug will also be fixed by this patch:
http://www.spinics.net/lists/target-devel/msg14560.html
which switches the tmr code to use the system workqueues.

For both, I am not sure if we need a dedicated workqueue since
it is not a performance path and I do not think we need WQ_MEM_RECLAIM
to make forward progress to free up memory like the block layer does.

Signed-off-by: Mike Christie <mchristi@redhat.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
1 parent 0a41457
Raw File
Tip revision: 207ee84133c00a8a2a5bdec94df4a5b37d78881c authored by Mike Christie on 02 March 2017, 05:13:26 UTC
target: Use system workqueue for ALUA transitions
Tip revision: 207ee84
test_static_key_base.c 
/*
 * Kernel module for testing static keys.
 *
 * Copyright 2015 Akamai Technologies Inc. All Rights Reserved
 *
 * Authors:
 *      Jason Baron       <jbaron@akamai.com>
 *
 * This software is licensed under the terms of the GNU General Public
 * License version 2, as published by the Free Software Foundation, and
 * may be copied, distributed, and modified under those terms.
 *
 * 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.
 */

#include <linux/module.h>
#include <linux/jump_label.h>

/* old keys */
struct static_key base_old_true_key = STATIC_KEY_INIT_TRUE;
EXPORT_SYMBOL_GPL(base_old_true_key);
struct static_key base_inv_old_true_key = STATIC_KEY_INIT_TRUE;
EXPORT_SYMBOL_GPL(base_inv_old_true_key);
struct static_key base_old_false_key = STATIC_KEY_INIT_FALSE;
EXPORT_SYMBOL_GPL(base_old_false_key);
struct static_key base_inv_old_false_key = STATIC_KEY_INIT_FALSE;
EXPORT_SYMBOL_GPL(base_inv_old_false_key);

/* new keys */
DEFINE_STATIC_KEY_TRUE(base_true_key);
EXPORT_SYMBOL_GPL(base_true_key);
DEFINE_STATIC_KEY_TRUE(base_inv_true_key);
EXPORT_SYMBOL_GPL(base_inv_true_key);
DEFINE_STATIC_KEY_FALSE(base_false_key);
EXPORT_SYMBOL_GPL(base_false_key);
DEFINE_STATIC_KEY_FALSE(base_inv_false_key);
EXPORT_SYMBOL_GPL(base_inv_false_key);

static void invert_key(struct static_key *key)
{
	if (static_key_enabled(key))
		static_key_disable(key);
	else
		static_key_enable(key);
}

static int __init test_static_key_base_init(void)
{
	invert_key(&base_inv_old_true_key);
	invert_key(&base_inv_old_false_key);
	invert_key(&base_inv_true_key.key);
	invert_key(&base_inv_false_key.key);

	return 0;
}

static void __exit test_static_key_base_exit(void)
{
}

module_init(test_static_key_base_init);
module_exit(test_static_key_base_exit);

MODULE_AUTHOR("Jason Baron <jbaron@akamai.com>");
MODULE_LICENSE("GPL");
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