netdev - [PATCH net 3/7] mlxsw: core: Do not use WQ_MEM

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Message-ID: <20190410065758.21199-4-idosch@mellanox.com>
Date:   Wed, 10 Apr 2019 06:58:14 +0000
From:   Ido Schimmel <idosch@...lanox.com>
To:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>
CC:     "davem@...emloft.net" <davem@...emloft.net>,
        Jiri Pirko <jiri@...lanox.com>, mlxsw <mlxsw@...lanox.com>,
        Ido Schimmel <idosch@...lanox.com>
Subject: [PATCH net 3/7] mlxsw: core: Do not use WQ_MEM_RECLAIM for mlxsw
 ordered workqueue

The ordered workqueue is used to offload various objects such as routes
and neighbours in the order they are notified.

It should not be called as part of memory reclaim path, so remove the
WQ_MEM_RECLAIM flag. This can also result in a warning [1], if a worker
tries to flush a non-WQ_MEM_RECLAIM workqueue.

[1]
[97703.542861] workqueue: WQ_MEM_RECLAIM mlxsw_core_ordered:mlxsw_sp_router_fib6_event_work [mlxsw_spectrum] is flushing !WQ_MEM_RECLAIM events:rht_deferred_worker
[97703.542884] WARNING: CPU: 1 PID: 32492 at kernel/workqueue.c:2605 check_flush_dependency+0xb5/0x130
...
[97703.542988] Hardware name: Mellanox Technologies Ltd. MSN3700C/VMOD0008, BIOS 5.11 10/10/2018
[97703.543049] Workqueue: mlxsw_core_ordered mlxsw_sp_router_fib6_event_work [mlxsw_spectrum]
[97703.543061] RIP: 0010:check_flush_dependency+0xb5/0x130
...
[97703.543071] RSP: 0018:ffffb3f08137bc00 EFLAGS: 00010086
[97703.543076] RAX: 0000000000000000 RBX: ffff96e07740ae00 RCX: 0000000000000000
[97703.543080] RDX: 0000000000000094 RSI: ffffffff82dc1934 RDI: 0000000000000046
[97703.543084] RBP: ffffb3f08137bc20 R08: ffffffff82dc18a0 R09: 00000000000225c0
[97703.543087] R10: 0000000000000000 R11: 0000000000007eec R12: ffffffff816e4ee0
[97703.543091] R13: ffff96e06f6a5c00 R14: ffff96e077ba7700 R15: ffffffff812ab0c0
[97703.543097] FS: 0000000000000000(0000) GS:ffff96e077a80000(0000) knlGS:0000000000000000
[97703.543101] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[97703.543104] CR2: 00007f8cd135b280 CR3: 00000001e860e003 CR4: 00000000003606e0
[97703.543109] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[97703.543112] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[97703.543115] Call Trace:
[97703.543129] __flush_work+0xbd/0x1e0
[97703.543137] ? __cancel_work_timer+0x136/0x1b0
[97703.543145] ? pwq_dec_nr_in_flight+0x49/0xa0
[97703.543154] __cancel_work_timer+0x136/0x1b0
[97703.543175] ? mlxsw_reg_trans_bulk_wait+0x145/0x400 [mlxsw_core]
[97703.543184] cancel_work_sync+0x10/0x20
[97703.543191] rhashtable_free_and_destroy+0x23/0x140
[97703.543198] rhashtable_destroy+0xd/0x10
[97703.543254] mlxsw_sp_fib_destroy+0xb1/0xf0 [mlxsw_spectrum]
[97703.543310] mlxsw_sp_vr_put+0xa8/0xc0 [mlxsw_spectrum]
[97703.543364] mlxsw_sp_fib_node_put+0xbf/0x140 [mlxsw_spectrum]
[97703.543418] ? mlxsw_sp_fib6_entry_destroy+0xe8/0x110 [mlxsw_spectrum]
[97703.543475] mlxsw_sp_router_fib6_event_work+0x6cd/0x7f0 [mlxsw_spectrum]
[97703.543484] process_one_work+0x1fd/0x400
[97703.543493] worker_thread+0x34/0x410
[97703.543500] kthread+0x121/0x140
[97703.543507] ? process_one_work+0x400/0x400
[97703.543512] ? kthread_park+0x90/0x90
[97703.543523] ret_from_fork+0x35/0x40

Fixes: a3832b31898f ("mlxsw: core: Create an ordered workqueue for FIB offload")
Signed-off-by: Ido Schimmel <idosch@...lanox.com>
Reported-by: Semion Lisyansky <semionl@...lanox.com>
Acked-by: Jiri Pirko <jiri@...lanox.com>
---
 drivers/net/ethernet/mellanox/mlxsw/core.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/mellanox/mlxsw/core.c b/drivers/net/ethernet/mellanox/mlxsw/core.c
index 91cd6fa42e9a..2c0e3281bd7a 100644
--- a/drivers/net/ethernet/mellanox/mlxsw/core.c
+++ b/drivers/net/ethernet/mellanox/mlxsw/core.c
@@ -1961,7 +1961,7 @@ static int __init mlxsw_core_module_init(void)
 	mlxsw_wq = alloc_workqueue(mlxsw_core_driver_name, WQ_MEM_RECLAIM, 0);
 	if (!mlxsw_wq)
 		return -ENOMEM;
-	mlxsw_owq = alloc_ordered_workqueue("%s_ordered", WQ_MEM_RECLAIM,
+	mlxsw_owq = alloc_ordered_workqueue("%s_ordered", 0,
 					    mlxsw_core_driver_name);
 	if (!mlxsw_owq) {
 		err = -ENOMEM;
-- 
2.20.1