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[3/3] target: Use system workqueue for ALUA transitions

Message ID 1488431606-15373-4-git-send-email-mchristi@redhat.com (mailing list archive)
State Superseded
Headers show

Commit Message

Mike Christie March 2, 2017, 5:13 a.m. UTC
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.

This bug will also be fixed by this patch:
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>
 drivers/target/target_core_alua.c | 8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)
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diff --git a/drivers/target/target_core_alua.c b/drivers/target/target_core_alua.c
index 5b5a1e2..58bf5e6 100644
--- a/drivers/target/target_core_alua.c
+++ b/drivers/target/target_core_alua.c
@@ -1121,13 +1121,11 @@  static int core_alua_do_transition_tg_pt(
 		unsigned long transition_tmo;
 		transition_tmo = tg_pt_gp->tg_pt_gp_implicit_trans_secs * HZ;
-		queue_delayed_work(tg_pt_gp->tg_pt_gp_dev->tmr_wq,
-				   &tg_pt_gp->tg_pt_gp_transition_work,
-				   transition_tmo);
+		schedule_delayed_work(&tg_pt_gp->tg_pt_gp_transition_work,
+				      transition_tmo);
 	} else {
 		tg_pt_gp->tg_pt_gp_transition_complete = &wait;
-		queue_delayed_work(tg_pt_gp->tg_pt_gp_dev->tmr_wq,
-				   &tg_pt_gp->tg_pt_gp_transition_work, 0);
+		schedule_delayed_work(&tg_pt_gp->tg_pt_gp_transition_work, 0);
 		tg_pt_gp->tg_pt_gp_transition_complete = NULL;