From 33940d09937276cd3c81f2874faf43e37c2db0e2 Mon Sep 17 00:00:00 2001 From: Joern Engel Date: Tue, 16 Sep 2014 16:23:12 -0400 Subject: target: encapsulate smp_mb__after_atomic() The target code has a rather generous helping of smp_mb__after_atomic() throughout the code base. Most atomic operations were followed by one and none were preceded by smp_mb__before_atomic(), nor accompanied by a comment explaining the need for a barrier. Instead of trying to prove for every case whether or not it is needed, this patch introduces atomic_inc_mb() and atomic_dec_mb(), which explicitly include the memory barriers before and after the atomic operation. For now they are defined in a target header, although they could be of general use. Most of the existing atomic/mb combinations were replaced by the new helpers. In a few cases the atomic was sandwiched in spin_lock/spin_unlock and I simply removed the barrier. I suspect that in most cases the correct conversion would have been to drop the barrier. I also suspect that a few cases exist where a) the barrier was necessary and b) a second barrier before the atomic would have been necessary and got added by this patch. Signed-off-by: Joern Engel Signed-off-by: Nicholas Bellinger --- drivers/target/target_core_alua.c | 33 ++++++++++----------------------- 1 file changed, 10 insertions(+), 23 deletions(-) (limited to 'drivers/target/target_core_alua.c') diff --git a/drivers/target/target_core_alua.c b/drivers/target/target_core_alua.c index fbc5ebb5f761..fb87780929d2 100644 --- a/drivers/target/target_core_alua.c +++ b/drivers/target/target_core_alua.c @@ -392,8 +392,7 @@ target_emulate_set_target_port_groups(struct se_cmd *cmd) if (tg_pt_id != tg_pt_gp->tg_pt_gp_id) continue; - atomic_inc(&tg_pt_gp->tg_pt_gp_ref_cnt); - smp_mb__after_atomic(); + atomic_inc_mb(&tg_pt_gp->tg_pt_gp_ref_cnt); spin_unlock(&dev->t10_alua.tg_pt_gps_lock); @@ -403,8 +402,7 @@ target_emulate_set_target_port_groups(struct se_cmd *cmd) found = true; spin_lock(&dev->t10_alua.tg_pt_gps_lock); - atomic_dec(&tg_pt_gp->tg_pt_gp_ref_cnt); - smp_mb__after_atomic(); + atomic_dec_mb(&tg_pt_gp->tg_pt_gp_ref_cnt); break; } spin_unlock(&dev->t10_alua.tg_pt_gps_lock); @@ -998,8 +996,7 @@ static void core_alua_do_transition_tg_pt_work(struct work_struct *work) * every I_T nexus other than the I_T nexus on which the SET * TARGET PORT GROUPS command */ - atomic_inc(&mem->tg_pt_gp_mem_ref_cnt); - smp_mb__after_atomic(); + atomic_inc_mb(&mem->tg_pt_gp_mem_ref_cnt); spin_unlock(&tg_pt_gp->tg_pt_gp_lock); spin_lock_bh(&port->sep_alua_lock); @@ -1028,8 +1025,7 @@ static void core_alua_do_transition_tg_pt_work(struct work_struct *work) spin_unlock_bh(&port->sep_alua_lock); spin_lock(&tg_pt_gp->tg_pt_gp_lock); - atomic_dec(&mem->tg_pt_gp_mem_ref_cnt); - smp_mb__after_atomic(); + atomic_dec_mb(&mem->tg_pt_gp_mem_ref_cnt); } spin_unlock(&tg_pt_gp->tg_pt_gp_lock); /* @@ -1063,7 +1059,6 @@ static void core_alua_do_transition_tg_pt_work(struct work_struct *work) core_alua_dump_state(tg_pt_gp->tg_pt_gp_alua_pending_state)); spin_lock(&dev->t10_alua.tg_pt_gps_lock); atomic_dec(&tg_pt_gp->tg_pt_gp_ref_cnt); - smp_mb__after_atomic(); spin_unlock(&dev->t10_alua.tg_pt_gps_lock); if (tg_pt_gp->tg_pt_gp_transition_complete) @@ -1125,7 +1120,6 @@ static int core_alua_do_transition_tg_pt( */ spin_lock(&dev->t10_alua.tg_pt_gps_lock); atomic_inc(&tg_pt_gp->tg_pt_gp_ref_cnt); - smp_mb__after_atomic(); spin_unlock(&dev->t10_alua.tg_pt_gps_lock); if (!explicit && tg_pt_gp->tg_pt_gp_implicit_trans_secs) { @@ -1168,7 +1162,6 @@ int core_alua_do_port_transition( spin_lock(&local_lu_gp_mem->lu_gp_mem_lock); lu_gp = local_lu_gp_mem->lu_gp; atomic_inc(&lu_gp->lu_gp_ref_cnt); - smp_mb__after_atomic(); spin_unlock(&local_lu_gp_mem->lu_gp_mem_lock); /* * For storage objects that are members of the 'default_lu_gp', @@ -1184,8 +1177,7 @@ int core_alua_do_port_transition( l_tg_pt_gp->tg_pt_gp_alua_nacl = l_nacl; rc = core_alua_do_transition_tg_pt(l_tg_pt_gp, new_state, explicit); - atomic_dec(&lu_gp->lu_gp_ref_cnt); - smp_mb__after_atomic(); + atomic_dec_mb(&lu_gp->lu_gp_ref_cnt); return rc; } /* @@ -1198,8 +1190,7 @@ int core_alua_do_port_transition( lu_gp_mem_list) { dev = lu_gp_mem->lu_gp_mem_dev; - atomic_inc(&lu_gp_mem->lu_gp_mem_ref_cnt); - smp_mb__after_atomic(); + atomic_inc_mb(&lu_gp_mem->lu_gp_mem_ref_cnt); spin_unlock(&lu_gp->lu_gp_lock); spin_lock(&dev->t10_alua.tg_pt_gps_lock); @@ -1227,8 +1218,7 @@ int core_alua_do_port_transition( tg_pt_gp->tg_pt_gp_alua_port = NULL; tg_pt_gp->tg_pt_gp_alua_nacl = NULL; } - atomic_inc(&tg_pt_gp->tg_pt_gp_ref_cnt); - smp_mb__after_atomic(); + atomic_inc_mb(&tg_pt_gp->tg_pt_gp_ref_cnt); spin_unlock(&dev->t10_alua.tg_pt_gps_lock); /* * core_alua_do_transition_tg_pt() will always return @@ -1238,16 +1228,14 @@ int core_alua_do_port_transition( new_state, explicit); spin_lock(&dev->t10_alua.tg_pt_gps_lock); - atomic_dec(&tg_pt_gp->tg_pt_gp_ref_cnt); - smp_mb__after_atomic(); + atomic_dec_mb(&tg_pt_gp->tg_pt_gp_ref_cnt); if (rc) break; } spin_unlock(&dev->t10_alua.tg_pt_gps_lock); spin_lock(&lu_gp->lu_gp_lock); - atomic_dec(&lu_gp_mem->lu_gp_mem_ref_cnt); - smp_mb__after_atomic(); + atomic_dec_mb(&lu_gp_mem->lu_gp_mem_ref_cnt); } spin_unlock(&lu_gp->lu_gp_lock); @@ -1260,8 +1248,7 @@ int core_alua_do_port_transition( core_alua_dump_state(new_state)); } - atomic_dec(&lu_gp->lu_gp_ref_cnt); - smp_mb__after_atomic(); + atomic_dec_mb(&lu_gp->lu_gp_ref_cnt); return rc; } -- cgit v1.2.3