forked from Minki/linux
mainlining shenanigans
4fe7c2962e
With the addition of the IB/Core drain API, iw_cxgb4 supported drain by watching the CQs when the QP was out of RTS and signalling "drain complete" when the last CQE is polled. This, however, doesn't fully support the drain semantics. Namely, the drain logic is supposed to signal "drain complete" only when the application has _processed_ the last CQE, not just removed them from the CQ. Thus a small timing hole exists that can cause touch after free type bugs in applications using the drain API (nvmf, iSER, for example). So iw_cxgb4 needs a better solution. The iWARP Verbs spec mandates that "_at some point_ after the QP is moved to ERROR", the iWARP driver MUST synchronously fail post_send and post_recv calls. iw_cxgb4 was currently not allowing any posts once the QP is in ERROR. This was in part due to the fact that the HW queues for the QP in ERROR state are disabled at this point, so there wasn't much else to do but fail the post operation synchronously. This restriction is what drove the first drain implementation in iw_cxgb4 that has the above mentioned flaw. This patch changes iw_cxgb4 to allow post_send and post_recv WRs after the QP is moved to ERROR state for kernel mode users, thus still adhering to the Verbs spec for user mode users, but allowing flush WRs for kernel users. Since the HW queues are disabled, we just synthesize a CQE for this post, queue it to the SW CQ, and then call the CQ event handler. This enables proper drain operations for the various storage applications. Signed-off-by: Steve Wise <swise@opengridcomputing.com> Signed-off-by: Doug Ledford <dledford@redhat.com> |
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| README | ||
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.