2015f26cfa
For messages sent from the host to fw that solicit a reply from fw, the c4iw_wr_wait struct pointer is passed in the host->fw message, and included in the fw->host fw6_msg reply. This allows the sender to wait until the reply is received, and the code processing the ingress reply to wake up the sender. If c4iw_wait_for_reply() times out, however, we need to keep the c4iw_wr_wait object around in case the reply eventually does arrive. Otherwise we have touch-after-free bugs in the wake_up paths. This was hit due to a bad kernel driver that blocked ingress processing of cxgb4 for a long time, causing iw_cxgb4 timeouts, but eventually resuming ingress processing and thus hitting the touch-after-free bug. So I want to fix iw_cxgb4 such that we'll at least keep the wait object around until the reply comes. If it never comes we leak a small amount of memory, but if it does come late, we won't potentially crash the system. So add a kref struct in the c4iw_wr_wait struct, and take a reference before sending a message to FW that will generate a FW6 reply. And remove the reference (and potentially free the wait object) when the reply is processed. The ep code also uses the wr_wait for non FW6 CPL messages and doesn't embed the c4iw_wr_wait object in the message sent to firmware. So for those cases we add c4iw_wake_up_noref(). The mr/mw, cq, and qp object create/destroy paths do need this reference logic. For these paths, c4iw_ref_send_wait() is introduced to take the wr_wait reference, send the msg to fw, and then wait for the reply. So going forward, iw_cxgb4 either uses c4iw_ofld_send(), c4iw_wait_for_reply() and c4iw_wake_up_noref() like is done in the some of the endpoint logic, or c4iw_ref_send_wait() and c4iw_wake_up_deref() (formerly c4iw_wake_up()) when sending messages with the c4iw_wr_wait object pointer embedded in the message and resulting FW6 reply. Signed-off-by: Steve Wise <swise@opengridcomputing.com> Signed-off-by: Doug Ledford <dledford@redhat.com>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.