diff options
| author | Nicholas Bellinger <nab@linux-iscsi.org> | 2014-01-28 17:56:30 -0800 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2014-02-13 13:55:41 -0800 |
| commit | 96330e5ec172d304d84f214d551ed3e9f520188a (patch) | |
| tree | e2780918b3a7319c3ae16b50290de2437ee37081 | |
| parent | 6cb630d2d77349364f446d1db908d08f1877c768 (diff) | |
target: Fix percpu_ref_put race in transport_lun_remove_cmd
commit 5259a06ef97068b710f45d092a587e8d740f750f upstream.
This patch fixes a percpu_ref_put race for se_lun->lun_ref in
transport_lun_remove_cmd() where ->lun_ref could end up being
put more than once per command via different target completion
and fabric release contexts.
It adds a cmpxchg() for se_cmd->lun_ref_active to ensure that
percpu_ref_put() is only ever called once per se_cmd.
This bug was manifesting itself as a LUN shutdown regression
bug in >= v3.13 code, where percpu_ref_kill() would end up
hanging indefinately due to the incorrect percpu_ref count.
(Change se_cmd->lun_ref_active from bool -> int to force at
least a 4-byte cmpxchg with MIPS ll/sc ins. - Fengguang)
Reported-by: Tommy Apel <tommyapeldk@gmail.com>
Cc: Tommy Apel <tommyapeldk@gmail.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -rw-r--r-- | drivers/target/target_core_transport.c | 5 | ||||
| -rw-r--r-- | include/target/target_core_base.h | 2 |
2 files changed, 4 insertions, 3 deletions
diff --git a/drivers/target/target_core_transport.c b/drivers/target/target_core_transport.c index 91953da0f623..dee2be1f9171 100644 --- a/drivers/target/target_core_transport.c +++ b/drivers/target/target_core_transport.c @@ -568,10 +568,11 @@ static void transport_lun_remove_cmd(struct se_cmd *cmd) { struct se_lun *lun = cmd->se_lun; - if (!lun || !cmd->lun_ref_active) + if (!lun) return; - percpu_ref_put(&lun->lun_ref); + if (cmpxchg(&cmd->lun_ref_active, true, false)) + percpu_ref_put(&lun->lun_ref); } void transport_cmd_finish_abort(struct se_cmd *cmd, int remove) diff --git a/include/target/target_core_base.h b/include/target/target_core_base.h index 321301c0a643..e3569f829f7e 100644 --- a/include/target/target_core_base.h +++ b/include/target/target_core_base.h @@ -497,7 +497,7 @@ struct se_cmd { void *priv; /* Used for lun->lun_ref counting */ - bool lun_ref_active; + int lun_ref_active; }; struct se_ua { |