On 02/23/2017 07:25 PM, Chris Leech wrote: > Yikes, my git-send-email settings suppressed the important CCs. Sorry! > > Guilherme and Ilkka, can you comment about your testing results or review > please?
Hi Chris, thanks for looping me. Patch seems nice, I do have some points below, most nitpicks heheh Feel free to accept or not the suggestions! Also, you can add my: Reviewed-by: Guilherme G. Piccoli <[email protected]> > > - Chris Leech > > ----- Original Message ----- >> There's a rather long standing regression from commit >> 659743b [SCSI] libiscsi: Reduce locking contention in fast path >> Perhaps worth to follow the checkpatch "rule" of citing commits here? 659743b02c41 ("[SCSI] libiscsi: Reduce locking contention in fast path") >> Depending on iSCSI target behavior, it's possible to hit the case in >> iscsi_complete_task where the task is still on a pending list >> (!list_empty(&task->running)). When that happens the task is removed >> from the list while holding the session back_lock, but other task list >> modification occur under the frwd_lock. That leads to linked list >> corruption and eventually a panicked system. >> >> Rather than back out the session lock split entirely, in order to try >> and keep some of the performance gains this patch adds another lock to >> maintain the task lists integrity. >> >> Major enterprise supported kernels have been backing out the lock split >> for while now, thanks to the efforts at IBM where a lab setup has the >> most reliable reproducer I've seen on this issue. This patch has been >> tested there successfully. >> >> Signed-off-by: Chris Leech <[email protected]> Guess we're missing here: (a) Fixes: 659743b02c41 ("[SCSI] libiscsi: Reduce locking contention in fast path") (b) CC: <stable-email> #v3.15+ Also, would be nice to point the original reporter, if possible: Reported-by: Prashantha Subbarao <[email protected]> >> --- >> drivers/scsi/libiscsi.c | 26 +++++++++++++++++++++++++- >> include/scsi/libiscsi.h | 1 + >> 2 files changed, 26 insertions(+), 1 deletion(-) >> >> diff --git a/drivers/scsi/libiscsi.c b/drivers/scsi/libiscsi.c >> index 834d121..acb5ef3 100644 >> --- a/drivers/scsi/libiscsi.c >> +++ b/drivers/scsi/libiscsi.c >> @@ -560,8 +560,12 @@ static void iscsi_complete_task(struct iscsi_task *task, >> int state) >> WARN_ON_ONCE(task->state == ISCSI_TASK_FREE); >> task->state = state; >> >> - if (!list_empty(&task->running)) >> + spin_lock_bh(&conn->taskqueuelock); >> + if (!list_empty(&task->running)) { >> + WARN_ONCE(1, "iscsi_complete_task while task on list"); I'm retesting this patch right now, and again I saw this giant warning. Perhaps worth to make it pr_debug()? So, it can be enabled as user desire and don't alarm all users too much. Thanks, Guilherme >> list_del_init(&task->running); >> + } >> + spin_unlock_bh(&conn->taskqueuelock); >> >> if (conn->task == task) >> conn->task = NULL; >> @@ -783,7 +787,9 @@ __iscsi_conn_send_pdu(struct iscsi_conn *conn, struct >> iscsi_hdr *hdr, >> if (session->tt->xmit_task(task)) >> goto free_task; >> } else { >> + spin_lock_bh(&conn->taskqueuelock); >> list_add_tail(&task->running, &conn->mgmtqueue); >> + spin_unlock_bh(&conn->taskqueuelock); >> iscsi_conn_queue_work(conn); >> } >> >> @@ -1474,8 +1480,10 @@ void iscsi_requeue_task(struct iscsi_task *task) >> * this may be on the requeue list already if the xmit_task callout >> * is handling the r2ts while we are adding new ones >> */ >> + spin_lock_bh(&conn->taskqueuelock); >> if (list_empty(&task->running)) >> list_add_tail(&task->running, &conn->requeue); >> + spin_unlock_bh(&conn->taskqueuelock); >> iscsi_conn_queue_work(conn); >> } >> EXPORT_SYMBOL_GPL(iscsi_requeue_task); >> @@ -1512,22 +1520,26 @@ static int iscsi_data_xmit(struct iscsi_conn *conn) >> * only have one nop-out as a ping from us and targets should not >> * overflow us with nop-ins >> */ >> + spin_lock_bh(&conn->taskqueuelock); >> check_mgmt: >> while (!list_empty(&conn->mgmtqueue)) { >> conn->task = list_entry(conn->mgmtqueue.next, >> struct iscsi_task, running); >> list_del_init(&conn->task->running); >> + spin_unlock_bh(&conn->taskqueuelock); >> if (iscsi_prep_mgmt_task(conn, conn->task)) { >> /* regular RX path uses back_lock */ >> spin_lock_bh(&conn->session->back_lock); >> __iscsi_put_task(conn->task); >> spin_unlock_bh(&conn->session->back_lock); >> conn->task = NULL; >> + spin_lock_bh(&conn->taskqueuelock); >> continue; >> } >> rc = iscsi_xmit_task(conn); >> if (rc) >> goto done; >> + spin_lock_bh(&conn->taskqueuelock); >> } >> >> /* process pending command queue */ >> @@ -1535,19 +1547,24 @@ static int iscsi_data_xmit(struct iscsi_conn *conn) >> conn->task = list_entry(conn->cmdqueue.next, struct iscsi_task, >> running); >> list_del_init(&conn->task->running); >> + spin_unlock_bh(&conn->taskqueuelock); >> if (conn->session->state == ISCSI_STATE_LOGGING_OUT) { >> fail_scsi_task(conn->task, DID_IMM_RETRY); >> + spin_lock_bh(&conn->taskqueuelock); >> continue; >> } >> rc = iscsi_prep_scsi_cmd_pdu(conn->task); >> if (rc) { >> if (rc == -ENOMEM || rc == -EACCES) { >> + spin_lock_bh(&conn->taskqueuelock); >> list_add_tail(&conn->task->running, >> &conn->cmdqueue); >> conn->task = NULL; >> + spin_unlock_bh(&conn->taskqueuelock); >> goto done; >> } else >> fail_scsi_task(conn->task, DID_ABORT); >> + spin_lock_bh(&conn->taskqueuelock); >> continue; >> } >> rc = iscsi_xmit_task(conn); >> @@ -1558,6 +1575,7 @@ static int iscsi_data_xmit(struct iscsi_conn *conn) >> * we need to check the mgmt queue for nops that need to >> * be sent to aviod starvation >> */ >> + spin_lock_bh(&conn->taskqueuelock); >> if (!list_empty(&conn->mgmtqueue)) >> goto check_mgmt; >> } >> @@ -1577,12 +1595,15 @@ static int iscsi_data_xmit(struct iscsi_conn *conn) >> conn->task = task; >> list_del_init(&conn->task->running); >> conn->task->state = ISCSI_TASK_RUNNING; >> + spin_unlock_bh(&conn->taskqueuelock); >> rc = iscsi_xmit_task(conn); >> if (rc) >> goto done; >> + spin_lock_bh(&conn->taskqueuelock); >> if (!list_empty(&conn->mgmtqueue)) >> goto check_mgmt; >> } >> + spin_unlock_bh(&conn->taskqueuelock); >> spin_unlock_bh(&conn->session->frwd_lock); >> return -ENODATA; >> >> @@ -1738,7 +1759,9 @@ int iscsi_queuecommand(struct Scsi_Host *host, struct >> scsi_cmnd *sc) >> goto prepd_reject; >> } >> } else { >> + spin_lock_bh(&conn->taskqueuelock); >> list_add_tail(&task->running, &conn->cmdqueue); >> + spin_unlock_bh(&conn->taskqueuelock); >> iscsi_conn_queue_work(conn); >> } >> >> @@ -2896,6 +2919,7 @@ iscsi_conn_setup(struct iscsi_cls_session *cls_session, >> int dd_size, >> INIT_LIST_HEAD(&conn->mgmtqueue); >> INIT_LIST_HEAD(&conn->cmdqueue); >> INIT_LIST_HEAD(&conn->requeue); >> + spin_lock_init(&conn->taskqueuelock); >> INIT_WORK(&conn->xmitwork, iscsi_xmitworker); >> >> /* allocate login_task used for the login/text sequences */ >> diff --git a/include/scsi/libiscsi.h b/include/scsi/libiscsi.h >> index b0e275d..583875e 100644 >> --- a/include/scsi/libiscsi.h >> +++ b/include/scsi/libiscsi.h >> @@ -196,6 +196,7 @@ struct iscsi_conn { >> struct iscsi_task *task; /* xmit task in progress */ >> >> /* xmit */ >> + spinlock_t taskqueuelock; /* protects the next three >> lists */ >> struct list_head mgmtqueue; /* mgmt (control) xmit queue */ >> struct list_head cmdqueue; /* data-path cmd queue */ >> struct list_head requeue; /* tasks needing another run */ >> -- >> 2.9.3 >> >> > -- You received this message because you are subscribed to the Google Groups "open-iscsi" group. 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