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| author | Nicholas Bellinger <nab@linux-iscsi.org> | 2014-01-28 17:56:30 -0800 |
|---|---|---|
| committer | Nicholas Bellinger <nab@linux-iscsi.org> | 2014-01-30 03:58:34 -0800 |
| commit | 5259a06ef97068b710f45d092a587e8d740f750f (patch) | |
| tree | da2b4c9718b41cec6e5057a3da593cc93c44759c /drivers/target | |
| parent | ee291e63293146db64668e8d65eb35c97e8324f4 (diff) | |
| download | linux-stable-5259a06ef97068b710f45d092a587e8d740f750f.tar.gz linux-stable-5259a06ef97068b710f45d092a587e8d740f750f.tar.bz2 linux-stable-5259a06ef97068b710f45d092a587e8d740f750f.zip | |
target: Fix percpu_ref_put race in transport_lun_remove_cmd
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>
Cc: <stable@vger.kernel.org> #3.13+
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
Diffstat (limited to 'drivers/target')
| -rw-r--r-- | drivers/target/target_core_transport.c | 5 |
1 files changed, 3 insertions, 2 deletions
diff --git a/drivers/target/target_core_transport.c b/drivers/target/target_core_transport.c index 51a9736be726..c50fd9f11aab 100644 --- a/drivers/target/target_core_transport.c +++ b/drivers/target/target_core_transport.c @@ -594,10 +594,11 @@ 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) |