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2019-01-14aio-posix: Fix concurrent aio_poll/set_fd_handler.Remy Noel1-38/+29
It is possible for an io_poll callback to be concurrently executed along with an aio_set_fd_handlers. This can cause all sorts of problems, like a NULL callback or a bad opaque pointer. This changes set_fd_handlers so that it no longer modify existing handlers entries and instead, always insert those after having proper initialisation. Tested-by: Stefan Hajnoczi <stefanha@redhat.com> Signed-off-by: Remy Noel <remy.noel@blade-group.com> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com> Reviewed-by: Paolo Bonzini <pbonzini@redhat.com> Message-id: 20181220152030.28035-3-remy.noel@blade-group.com Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2018-08-15aio: Do aio_notify_accept only during blocking aio_pollFam Zheng1-1/+2
An aio_notify() pairs with an aio_notify_accept(). The former should happen in the main thread or a vCPU thread, and the latter should be done in the IOThread. There is one rare case that the main thread or vCPU thread may "steal" the aio_notify() event just raised by itself, in bdrv_set_aio_context() [1]. The sequence is like this: main thread IO Thread =============================================================== bdrv_drained_begin() aio_disable_external(ctx) aio_poll(ctx, true) ctx->notify_me += 2 ... bdrv_drained_end() ... aio_notify() ... bdrv_set_aio_context() aio_poll(ctx, false) [1] aio_notify_accept(ctx) ppoll() /* Hang! */ [1] is problematic. It will clear the ctx->notifier event so that the blocked ppoll() will not return. (For the curious, this bug was noticed when booting a number of VMs simultaneously in RHV. One or two of the VMs will hit this race condition, making the VIRTIO device unresponsive to I/O commands. When it hangs, Seabios is busy waiting for a read request to complete (read MBR), right after initializing the virtio-blk-pci device, using 100% guest CPU. See also https://bugzilla.redhat.com/show_bug.cgi?id=1562750 for the original bug analysis.) aio_notify() only injects an event when ctx->notify_me is set, correspondingly aio_notify_accept() is only useful when ctx->notify_me _was_ set. Move the call to it into the "blocking" branch. This will effectively skip [1] and fix the hang. Furthermore, blocking aio_poll is only allowed on home thread (in_aio_context_home_thread), because otherwise two blocking aio_poll()'s can steal each other's ctx->notifier event and cause hanging just like described above. Cc: qemu-stable@nongnu.org Suggested-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Fam Zheng <famz@redhat.com> Message-Id: <20180809132259.18402-3-famz@redhat.com> Signed-off-by: Fam Zheng <famz@redhat.com>
2018-05-18iothread: fix epollfd leak in the process of delIOThreadJie Wang1-0/+4
When we call addIOThread, the epollfd created in aio_context_setup, but not close it in the process of delIOThread, so the epollfd will leak. Reorder the code in aio_epoll_disable and reuse it. Signed-off-by: Jie Wang <wangjie88@huawei.com> Message-Id: <1526517763-11108-1-git-send-email-wangjie88@huawei.com> Reviewed-by: Fam Zheng <famz@redhat.com> Reviewed-by: Peter Xu <peterx@redhat.com> [Mention change to aio_epoll_disable in commit message. - Fam] Signed-off-by: Fam Zheng <famz@redhat.com>
2018-03-26iothread: fix breakage on windowsPeter Xu1-1/+3
OOB can enable iothread for parsing even on Windows. We need some tunes to enable that on Windows otherwise it'll break Windows users. This patch fixes the breakage on Windows with qemu-system-ppc.exe. Reported-by: Howard Spoelstra <hsp.cat7@gmail.com> Tested-by: Howard Spoelstra <hsp.cat7@gmail.com> Suggested-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Peter Xu <peterx@redhat.com> Message-Id: <20180322085630.23654-1-peterx@redhat.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2017-07-17util/aio-win32: Only select on what we are actually waiting forAlistair Francis1-3/+10
Signed-off-by: Alistair Francis <alistair.francis@xilinx.com> Acked-by: Edgar E. Iglesias <edgar.iglesias@xilinx.com> Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org> Message-id: 9307b70e9876c4e9e3c4478524a32a23a3d5dd05.1499368180.git.alistair.francis@xilinx.com Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2017-02-21async: remove unnecessary inc/dec pairsPaolo Bonzini1-4/+4
Pull the increment/decrement pair out of aio_bh_poll and into the callers. Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Reviewed-by: Fam Zheng <famz@redhat.com> Reviewed-by: Daniel P. Berrange <berrange@redhat.com> Message-id: 20170213135235.12274-18-pbonzini@redhat.com Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2017-02-21aio-posix: partially inline aio_dispatch into aio_pollPaolo Bonzini1-9/+4
This patch prepares for the removal of unnecessary lockcnt inc/dec pairs. Extract the dispatching loop for file descriptor handlers into a new function aio_dispatch_handlers, and then inline aio_dispatch into aio_poll. aio_dispatch can now become void. Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Reviewed-by: Fam Zheng <famz@redhat.com> Reviewed-by: Daniel P. Berrange <berrange@redhat.com> Message-id: 20170213135235.12274-17-pbonzini@redhat.com Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2017-02-21block: explicitly acquire aiocontext in callbacks that need itPaolo Bonzini1-6/+0
This covers both file descriptor callbacks and polling callbacks, since they execute related code. Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Reviewed-by: Fam Zheng <famz@redhat.com> Reviewed-by: Daniel P. Berrange <berrange@redhat.com> Message-id: 20170213135235.12274-14-pbonzini@redhat.com Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2017-02-21block: explicitly acquire aiocontext in timers that need itPaolo Bonzini1-2/+0
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Reviewed-by: Fam Zheng <famz@redhat.com> Reviewed-by: Daniel P. Berrange <berrange@redhat.com> Message-id: 20170213135235.12274-13-pbonzini@redhat.com Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2017-02-21aio: push aio_context_acquire/release down to dispatchingPaolo Bonzini1-8/+7
The AioContext data structures are now protected by list_lock and/or they are walked with FOREACH_RCU primitives. There is no need anymore to acquire the AioContext for the entire duration of aio_dispatch. Instead, just acquire it before and after invoking the callbacks. The next step is then to push it further down. Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Reviewed-by: Fam Zheng <famz@redhat.com> Reviewed-by: Daniel P. Berrange <berrange@redhat.com> Message-id: 20170213135235.12274-12-pbonzini@redhat.com Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2017-02-21block: move AioContext, QEMUTimer, main-loop to libqemuutilPaolo Bonzini1-0/+421
AioContext is fairly self contained, the only dependency is QEMUTimer but that in turn doesn't need anything else. So move them out of block-obj-y to avoid introducing a dependency from io/ to block-obj-y. main-loop and its dependency iohandler also need to be moved, because later in this series io/ will call iohandler_get_aio_context. [Changed copyright "the QEMU team" to "other QEMU contributors" as suggested by Daniel Berrange and agreed by Paolo. --Stefan] Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Reviewed-by: Fam Zheng <famz@redhat.com> Message-id: 20170213135235.12274-2-pbonzini@redhat.com Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
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