From 760bf578edf8122f2503a3a6a3f4b0de3b6ce0bb Mon Sep 17 00:00:00 2001 From: Mike Christie Date: Thu, 2 Mar 2017 04:59:50 -0600 Subject: [PATCH] target: fix race during implicit transition work flushes This fixes the following races: 1. core_alua_do_transition_tg_pt could have read tg_pt_gp_alua_access_state and gone into this if chunk: if (!explicit && atomic_read(&tg_pt_gp->tg_pt_gp_alua_access_state) == ALUA_ACCESS_STATE_TRANSITION) { and then core_alua_do_transition_tg_pt_work could update the state. core_alua_do_transition_tg_pt would then only set tg_pt_gp_alua_pending_state and the tg_pt_gp_alua_access_state would not get updated with the second calls state. 2. core_alua_do_transition_tg_pt could be setting tg_pt_gp_transition_complete while the tg_pt_gp_transition_work is already completing. core_alua_do_transition_tg_pt then waits on the completion that will never be called. To handle these issues, we just call flush_work which will return when core_alua_do_transition_tg_pt_work has completed so there is no need to do the complete/wait. And, if core_alua_do_transition_tg_pt_work was running, instead of trying to sneak in the state change, we just schedule up another core_alua_do_transition_tg_pt_work call. Note that this does not handle a possible race where there are multiple threads call core_alua_do_transition_tg_pt at the same time. I think we need a mutex in target_tg_pt_gp_alua_access_state_store. Signed-off-by: Mike Christie Signed-off-by: Nicholas Bellinger --- drivers/target/target_core_alua.c | 10 +--------- 1 file changed, 1 insertion(+), 9 deletions(-) diff --git a/drivers/target/target_core_alua.c b/drivers/target/target_core_alua.c index 252d4e4b7b33..fd7c16a7ca6e 100644 --- a/drivers/target/target_core_alua.c +++ b/drivers/target/target_core_alua.c @@ -1079,16 +1079,8 @@ static int core_alua_do_transition_tg_pt( /* * Flush any pending transitions */ - if (!explicit && atomic_read(&tg_pt_gp->tg_pt_gp_alua_access_state) == - ALUA_ACCESS_STATE_TRANSITION) { - /* Just in case */ - tg_pt_gp->tg_pt_gp_alua_pending_state = new_state; - tg_pt_gp->tg_pt_gp_transition_complete = &wait; + if (!explicit) flush_work(&tg_pt_gp->tg_pt_gp_transition_work); - wait_for_completion(&wait); - tg_pt_gp->tg_pt_gp_transition_complete = NULL; - return 0; - } /* * Save the old primary ALUA access state, and set the current state -- 2.20.1