Patchwork [3.5.y.z,extended,stable] Patch "target/iscsi: don't corrupt bh_count in" has been added to staging queue

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Submitter Luis Henriques
Date June 25, 2013, 9:30 a.m.
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Download mbox | patch
Permalink /patch/254089/
State New
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Luis Henriques - June 25, 2013, 9:30 a.m.
This is a note to let you know that I have just added a patch titled

    target/iscsi: don't corrupt bh_count in

to the linux-3.5.y-queue branch of the 3.5.y.z extended stable tree 
which can be found at:;a=shortlog;h=refs/heads/linux-3.5.y-queue

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.5.y.z tree, see



From fc97082133869b1501adbf67d3799d3b53d24036 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?J=C3=B6rn=20Engel?= <>
Date: Thu, 30 May 2013 16:36:51 -0400
Subject: [PATCH] target/iscsi: don't corrupt bh_count in

commit 574780fd5e6ec52bd43e0bdb777a19e4c4c6aa9c upstream.

Here is a fun one.  Bug seems to have been introduced by commit 140854cb,
almost two years ago.  I have no idea why we only started seeing it now,
but we did.

Rough callgraph:
`-> spin_lock_irqsave(&tpg->session_lock, flags);
`-> lio_tpg_shutdown_session()
    `-> iscsit_stop_time2retain_timer()
        `-> spin_unlock_bh(&se_tpg->session_lock);
        `-> spin_lock_bh(&se_tpg->session_lock);
`-> spin_unlock_irqrestore(&tpg->session_lock, flags);

core_tpg_set_initiator_node_queue_depth() used to call spin_lock_bh(),
but 140854cb changed that to spin_lock_irqsave().  However,
lio_tpg_shutdown_session() still claims to be called with spin_lock_bh()
held, as does iscsit_stop_time2retain_timer():
 *      Called with spin_lock_bh(&struct se_portal_group->session_lock) held

Stale documentation is mostly annoying, but in this case the dropping
the lock with the _bh variant is plain wrong.  It is also wrong to drop
locks two functions below the lock-holder, but I will ignore that bit
for now.

After some more locking and unlocking we eventually hit this backtrace:
------------[ cut here ]------------
WARNING: at kernel/softirq.c:159 local_bh_enable_ip+0xe8/0x100()
Pid: 24645, comm: Tainted: G           O 3.6.11+
Call Trace:
 [<ffffffff8103e5ff>] warn_slowpath_common+0x7f/0xc0
 [<ffffffffa040ae37>] ? iscsit_inc_conn_usage_count+0x37/0x50 [iscsi_target_mod]
 [<ffffffff8103e65a>] warn_slowpath_null+0x1a/0x20
 [<ffffffff810472f8>] local_bh_enable_ip+0xe8/0x100
 [<ffffffff815b8365>] _raw_spin_unlock_bh+0x15/0x20
 [<ffffffffa040ae37>] iscsit_inc_conn_usage_count+0x37/0x50 [iscsi_target_mod]
 [<ffffffffa041149a>] iscsit_stop_session+0xfa/0x1c0 [iscsi_target_mod]
 [<ffffffffa0417fab>] lio_tpg_shutdown_session+0x7b/0x90 [iscsi_target_mod]
 [<ffffffffa033ede4>] core_tpg_set_initiator_node_queue_depth+0xe4/0x290 [target_core_mod]
 [<ffffffffa0409032>] iscsit_tpg_set_initiator_node_queue_depth+0x12/0x20 [iscsi_target_mod]
 [<ffffffffa0415c29>] lio_target_nacl_store_cmdsn_depth+0xa9/0x180 [iscsi_target_mod]
 [<ffffffffa0331b49>] target_fabric_nacl_base_attr_store+0x39/0x40 [target_core_mod]
 [<ffffffff811b857d>] configfs_write_file+0xbd/0x120
 [<ffffffff81148f36>] vfs_write+0xc6/0x180
 [<ffffffff81149251>] sys_write+0x51/0x90
 [<ffffffff815c0969>] system_call_fastpath+0x16/0x1b
---[ end trace 3747632b9b164652 ]---

As a pure band-aid, this patch drops the _bh.

Signed-off-by: Joern Engel <>
Signed-off-by: Nicholas Bellinger <>
Signed-off-by: Luis Henriques <>
 drivers/target/iscsi/iscsi_target_erl0.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)



diff --git a/drivers/target/iscsi/iscsi_target_erl0.c b/drivers/target/iscsi/iscsi_target_erl0.c
index 1a02016..e768bfa 100644
--- a/drivers/target/iscsi/iscsi_target_erl0.c
+++ b/drivers/target/iscsi/iscsi_target_erl0.c
@@ -834,11 +834,11 @@  extern int iscsit_stop_time2retain_timer(struct iscsi_session *sess)
 		return 0;

 	sess->time2retain_timer_flags |= ISCSI_TF_STOP;
-	spin_unlock_bh(&se_tpg->session_lock);
+	spin_unlock(&se_tpg->session_lock);


-	spin_lock_bh(&se_tpg->session_lock);
+	spin_lock(&se_tpg->session_lock);
 	sess->time2retain_timer_flags &= ~ISCSI_TF_RUNNING;
 	pr_debug("Stopped Time2Retain Timer for SID: %u\n",