iscsi-target: Fix potential deadlock on lock taken in timer
authorRoland Dreier <roland@purestorage.com>
Tue, 6 Nov 2012 02:02:40 +0000 (18:02 -0800)
committerNicholas Bellinger <nab@linux-iscsi.org>
Thu, 8 Nov 2012 04:12:07 +0000 (20:12 -0800)
commit998866b0740f128fd2c107c167c8385406dadae0
treed923a10a89785c75d3fb93949bd72b4332930efb
parentbb7a8c8eb9678666fb05f3bc542581365399a161
iscsi-target: Fix potential deadlock on lock taken in timer

We need to disable BHs when taking sess_idr_lock because the
iscsit_handle_time2retain_timeout() timer function takes
se_tpg->session_lock, and iscsit_close_session() nests sess_idr_lock
inside se_tpg->session_lock.  So if the timer can run inside
sess_idr_lock, we have a potential AB-BA deadlock.

Fix this by disabling BHs when taking sess_idr_lock.  This was found
because of a lockdep warning, but it looks like a real (if highly
theoretical) deadlock.  In any case avoiding lockdep spew so that we can
find other issues is a worthy cause.

Signed-off-by: Roland Dreier <roland@purestorage.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
drivers/target/iscsi/iscsi_target_login.c