| Message ID | 1433821856-2815280-7-git-send-email-calvinowens@fb.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Mon, Jun 08, 2015 at 08:50:56PM -0700, Calvin Owens wrote: > Since the fw_event deletes itself from the list, cleanup_queue() can > walk onto garbage pointers or walk off into freed memory. > > This refactors the code in _scsih_fw_event_cleanup_queue() to not > iterate over the fw_event_list without a lock. I think this really should be folded into the previous one, with the fixes in this one the other refcounting change don't make a whole lot sense. > +static struct fw_event_work *dequeue_next_fw_event(struct MPT2SAS_ADAPTER *ioc) > +{ > + unsigned long flags; > + struct fw_event_work *fw_event = NULL; > + > + spin_lock_irqsave(&ioc->fw_event_lock, flags); > + if (!list_empty(&ioc->fw_event_list)) { > + fw_event = list_first_entry(&ioc->fw_event_list, > + struct fw_event_work, list); > + list_del_init(&fw_event->list); > + fw_event_work_get(fw_event); > + } > + spin_unlock_irqrestore(&ioc->fw_event_lock, flags); > + > + return fw_event; Shouldn't we have a reference for each item on the list that gets transfer to whomever removes it from the list? Additionally _firmware_event_work should call dequeue_next_fw_event first in the function so that item is off the list before we process it, and can then just drop the reference once it's done. -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Friday 07/03 at 09:02 -0700, Christoph Hellwig wrote: > On Mon, Jun 08, 2015 at 08:50:56PM -0700, Calvin Owens wrote: > > Since the fw_event deletes itself from the list, cleanup_queue() can > > walk onto garbage pointers or walk off into freed memory. > > > > This refactors the code in _scsih_fw_event_cleanup_queue() to not > > iterate over the fw_event_list without a lock. > > I think this really should be folded into the previous one, with the > fixes in this one the other refcounting change don't make a whole lot > sense. > > > +static struct fw_event_work *dequeue_next_fw_event(struct MPT2SAS_ADAPTER *ioc) > > +{ > > + unsigned long flags; > > + struct fw_event_work *fw_event = NULL; > > + > > + spin_lock_irqsave(&ioc->fw_event_lock, flags); > > + if (!list_empty(&ioc->fw_event_list)) { > > + fw_event = list_first_entry(&ioc->fw_event_list, > > + struct fw_event_work, list); > > + list_del_init(&fw_event->list); > > + fw_event_work_get(fw_event); > > + } > > + spin_unlock_irqrestore(&ioc->fw_event_lock, flags); > > + > > + return fw_event; > > Shouldn't we have a reference for each item on the list that gets > transfer to whomever removes it from the list? Yes, this was a bit weird the way I did it. I redid this in v2, hopefully it's clearer. > Additionally _firmware_event_work should call dequeue_next_fw_event > first in the function so that item is off the list before we process > it, and can then just drop the reference once it's done. That works: cleanup_queue() won't wait on some already-running events, but destroy_workqueue() drains the wq, so we won't run ahead and free things from under the fw_event when unwinding. -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/drivers/scsi/mpt2sas/mpt2sas_scsih.c b/drivers/scsi/mpt2sas/mpt2sas_scsih.c index 8d8c814..f504e28 100644 --- a/drivers/scsi/mpt2sas/mpt2sas_scsih.c +++ b/drivers/scsi/mpt2sas/mpt2sas_scsih.c @@ -2939,6 +2939,23 @@ mpt2sas_port_enable_complete(struct MPT2SAS_ADAPTER *ioc) fw_event_work_put(fw_event); } +static struct fw_event_work *dequeue_next_fw_event(struct MPT2SAS_ADAPTER *ioc) +{ + unsigned long flags; + struct fw_event_work *fw_event = NULL; + + spin_lock_irqsave(&ioc->fw_event_lock, flags); + if (!list_empty(&ioc->fw_event_list)) { + fw_event = list_first_entry(&ioc->fw_event_list, + struct fw_event_work, list); + list_del_init(&fw_event->list); + fw_event_work_get(fw_event); + } + spin_unlock_irqrestore(&ioc->fw_event_lock, flags); + + return fw_event; +} + /** * _scsih_fw_event_cleanup_queue - cleanup event queue * @ioc: per adapter object @@ -2951,17 +2968,18 @@ mpt2sas_port_enable_complete(struct MPT2SAS_ADAPTER *ioc) static void _scsih_fw_event_cleanup_queue(struct MPT2SAS_ADAPTER *ioc) { - struct fw_event_work *fw_event, *next; + struct fw_event_work *fw_event; if (list_empty(&ioc->fw_event_list) || !ioc->firmware_event_thread || in_interrupt()) return; - list_for_each_entry_safe(fw_event, next, &ioc->fw_event_list, list) { + while ((fw_event = dequeue_next_fw_event(ioc))) { if (cancel_delayed_work_sync(&fw_event->delayed_work)) { _scsih_fw_event_free(ioc, fw_event); continue; } + fw_event_work_put(fw_event); } }
Since the fw_event deletes itself from the list, cleanup_queue() can walk onto garbage pointers or walk off into freed memory. This refactors the code in _scsih_fw_event_cleanup_queue() to not iterate over the fw_event_list without a lock. Signed-off-by: Calvin Owens <calvinowens@fb.com> --- drivers/scsi/mpt2sas/mpt2sas_scsih.c | 22 ++++++++++++++++++++-- 1 file changed, 20 insertions(+), 2 deletions(-)