path: root/iothread.c
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2019-03-08iothread: document about why we need explicit aio_poll()Peter Xu
After consulting Paolo I know why we'd better keep the explicit aio_poll() in iothread_run(). Document it directly into the code so that future readers will know the answer from day one. Signed-off-by: Peter Xu <peterx@redhat.com> Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com> Message-id: 20190306115532.23025-6-peterx@redhat.com Message-Id: <20190306115532.23025-6-peterx@redhat.com> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2019-03-08iothread: push gcontext earlier in the thread_fnPeter Xu
We were pushing the context until right before running the gmainloop. Now since we have everything unconditionally, we can move this earlier. One benefit is that now it's done even before init_done_sem, so as long as the iothread user calls iothread_create() and completes, we know that the thread stack is ready. Signed-off-by: Peter Xu <peterx@redhat.com> Message-id: 20190306115532.23025-5-peterx@redhat.com Message-Id: <20190306115532.23025-5-peterx@redhat.com> [Tweaked comment wording as discussed with Peter Xu. --Stefan] Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2019-03-08iothread: create main loop unconditionallyPeter Xu
Since we've have the gcontext always there, create the main loop altogether. The iothread_run() is even cleaner. Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com> Signed-off-by: Peter Xu <peterx@redhat.com> Message-id: 20190306115532.23025-4-peterx@redhat.com Message-Id: <20190306115532.23025-4-peterx@redhat.com> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2019-03-08iothread: create the gcontext unconditionallyPeter Xu
In existing code we create the gcontext dynamically at the first access of the gcontext from caller. That can bring some complexity and potential races during using iothread. Since the context itself is not that big a resource, and we won't have millions of iothread, let's simply create the gcontext unconditionally. This will also be a preparation work further to move the thread context push operation earlier than before (now it's only pushed right before we want to start running the gmainloop). Removing the g_once since it's not necessary, while introducing a new run_gcontext boolean to show whether we want to run the gcontext. Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com> Signed-off-by: Peter Xu <peterx@redhat.com> Message-id: 20190306115532.23025-3-peterx@redhat.com Message-Id: <20190306115532.23025-3-peterx@redhat.com> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2019-03-08iothread: replace init_done_cond with a semaphorePeter Xu
Only sending an init-done message using lock+cond seems an overkill to me. Replacing it with a simpler semaphore. Meanwhile, init the semaphore unconditionally, then we can destroy it unconditionally too in finalize which seems cleaner. Signed-off-by: Peter Xu <peterx@redhat.com> Message-id: 20190306115532.23025-2-peterx@redhat.com Message-Id: <20190306115532.23025-2-peterx@redhat.com> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2019-02-12iothread: fix iothread hang when stop too soonPeter Xu
Lukas reported an hard to reproduce QMP iothread hang on s390 that QEMU might hang at pthread_join() of the QMP monitor iothread before quitting: Thread 1 #0 0x000003ffad10932c in pthread_join #1 0x0000000109e95750 in qemu_thread_join at /home/thuth/devel/qemu/util/qemu-thread-posix.c:570 #2 0x0000000109c95a1c in iothread_stop #3 0x0000000109bb0874 in monitor_cleanup #4 0x0000000109b55042 in main While the iothread is still in the main loop: Thread 4 #0 0x000003ffad0010e4 in ?? #1 0x000003ffad553958 in g_main_context_iterate.isra.19 #2 0x000003ffad553d90 in g_main_loop_run #3 0x0000000109c9585a in iothread_run at /home/thuth/devel/qemu/iothread.c:74 #4 0x0000000109e94752 in qemu_thread_start at /home/thuth/devel/qemu/util/qemu-thread-posix.c:502 #5 0x000003ffad10825a in start_thread #6 0x000003ffad00dcf2 in thread_start IMHO it's because there's a race between the main thread and iothread when stopping the thread in following sequence: main thread iothread =========== ============== aio_poll() iothread_get_g_main_context set iothread->worker_context iothread_stop schedule iothread_stop_bh execute iothread_stop_bh [1] set iothread->running=false (since main_loop==NULL so skip to quit main loop. Note: although main_loop is NULL but worker_context is not!) atomic_read(&iothread->worker_context) [2] create main_loop object g_main_loop_run() [3] pthread_join() [4] We can see that when execute iothread_stop_bh() at [1] it's possible that main_loop is still NULL because it's only created until the first check of the worker_context later at [2]. Then the iothread will hang in the main loop [3] and it'll starve the main thread too [4]. Here the simple solution should be that we check again the "running" variable before check against worker_context. CC: Thomas Huth <thuth@redhat.com> CC: Dr. David Alan Gilbert <dgilbert@redhat.com> CC: Stefan Hajnoczi <stefanha@redhat.com> CC: Lukáš Doktor <ldoktor@redhat.com> CC: Markus Armbruster <armbru@redhat.com> CC: Eric Blake <eblake@redhat.com> CC: Paolo Bonzini <pbonzini@redhat.com> Reported-by: Lukáš Doktor <ldoktor@redhat.com> Signed-off-by: Peter Xu <peterx@redhat.com> Tested-by: Thomas Huth <thuth@redhat.com> Message-id: 20190129051432.22023-1-peterx@redhat.com Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2018-10-12iothread: fix crash with invalid propertiesMarc-André Lureau
-object iothread,id=foo,? will crash qemu: qemu-system-x86_64:qemu-thread-posix.c:128: qemu_cond_destroy: Assertion `cond->initialized' failed. Use thread_id != -1 to check if iothread_complete() finished successfully and the mutex/cond have been initialized. Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com> Message-Id: <20180821100716.13803-1-marcandre.lureau@redhat.com> Signed-off-by: Fam Zheng <famz@redhat.com>
2018-04-10iothread: workaround glib bug which hangs qmp-testPeter Xu
Free the AIO context earlier than the GMainContext (if we have) to workaround a glib2 bug that GSource context pointer is not cleared even if the context has already been destroyed (while it should). The patch itself only changed the order to destroy the objects, no functional change at all. Without this workaround, we can encounter qmp-test hang with oob (and possibly any other use case when iothread is used with GMainContexts): #0 0x00007f35ffe45334 in __lll_lock_wait () from /lib64/libpthread.so.0 #1 0x00007f35ffe405d8 in _L_lock_854 () from /lib64/libpthread.so.0 #2 0x00007f35ffe404a7 in pthread_mutex_lock () from /lib64/libpthread.so.0 #3 0x00007f35fc5b9c9d in g_source_unref_internal (source=0x24f0600, context=0x7f35f0000960, have_lock=0) at gmain.c:1685 #4 0x0000000000aa6672 in aio_context_unref (ctx=0x24f0600) at /root/qemu/util/async.c:497 #5 0x000000000065851c in iothread_instance_finalize (obj=0x24f0380) at /root/qemu/iothread.c:129 #6 0x0000000000962d79 in object_deinit (obj=0x24f0380, type=0x242e960) at /root/qemu/qom/object.c:462 #7 0x0000000000962e0d in object_finalize (data=0x24f0380) at /root/qemu/qom/object.c:476 #8 0x0000000000964146 in object_unref (obj=0x24f0380) at /root/qemu/qom/object.c:924 #9 0x0000000000965880 in object_finalize_child_property (obj=0x24ec640, name=0x24efca0 "mon_iothread", opaque=0x24f0380) at /root/qemu/qom/object.c:1436 #10 0x0000000000962c33 in object_property_del_child (obj=0x24ec640, child=0x24f0380, errp=0x0) at /root/qemu/qom/object.c:436 #11 0x0000000000962d26 in object_unparent (obj=0x24f0380) at /root/qemu/qom/object.c:455 #12 0x0000000000658f00 in iothread_destroy (iothread=0x24f0380) at /root/qemu/iothread.c:365 #13 0x00000000004c67a8 in monitor_cleanup () at /root/qemu/monitor.c:4663 #14 0x0000000000669e27 in main (argc=16, argv=0x7ffc8b1ae2f8, envp=0x7ffc8b1ae380) at /root/qemu/vl.c:4749 The glib2 bug is fixed in commit 26056558b ("gmain: allow g_source_get_context() on destroyed sources", 2012-07-30), so the first good version is glib2 2.33.10. But we still support building with glib as old as 2.28, so we need the workaround. Let's make sure we destroy the GSources first before its owner context until we drop support for glib older than 2.33.10. Signed-off-by: Peter Xu <peterx@redhat.com> Message-Id: <20180409083956.1780-1-peterx@redhat.com> Reviewed-by: Eric Blake <eblake@redhat.com> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com> Signed-off-by: Eric Blake <eblake@redhat.com>
2018-03-26iothread: fix breakage on windowsPeter Xu
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>
2018-03-08vl: introduce vm_shutdown()Stefan Hajnoczi
Commit 00d09fdbbae5f7864ce754913efc84c12fdf9f1a ("vl: pause vcpus before stopping iothreads") and commit dce8921b2baaf95974af8176406881872067adfa ("iothread: Stop threads before main() quits") tried to work around the fact that emulation was still active during termination by stopping iothreads. They suffer from race conditions: 1. virtio_scsi_handle_cmd_vq() racing with iothread_stop_all() hits the virtio_scsi_ctx_check() assertion failure because the BDS AioContext has been modified by iothread_stop_all(). 2. Guest vq kick racing with main loop termination leaves a readable ioeventfd that is handled by the next aio_poll() when external clients are enabled again, resulting in unwanted emulation activity. This patch obsoletes those commits by fully disabling emulation activity when vcpus are stopped. Use the new vm_shutdown() function instead of pause_all_vcpus() so that vm change state handlers are invoked too. Virtio devices will now stop their ioeventfds, preventing further emulation activity after vm_stop(). Note that vm_stop(RUN_STATE_SHUTDOWN) cannot be used because it emits a QMP STOP event that may affect existing clients. It is no longer necessary to call replay_disable_events() directly since vm_shutdown() does so already. Drop iothread_stop_all() since it is no longer used. Cc: Fam Zheng <famz@redhat.com> Cc: Kevin Wolf <kwolf@redhat.com> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com> Reviewed-by: Fam Zheng <famz@redhat.com> Acked-by: Paolo Bonzini <pbonzini@redhat.com> Message-id: 20180307144205.20619-5-stefanha@redhat.com Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2018-03-02qapi: Empty out qapi-schema.jsonMarkus Armbruster
The previous commit improved compile time by including less of the generated QAPI headers. This is impossible for stuff defined directly in qapi-schema.json, because that ends up in headers that that pull in everything. Move everything but include directives from qapi-schema.json to new sub-module qapi/misc.json, then include just the "misc" shard where possible. It's possible everywhere, except: * monitor.c needs qmp-command.h to get qmp_init_marshal() * monitor.c, ui/vnc.c and the generated qapi-event-FOO.c need qapi-event.h to get enum QAPIEvent Perhaps we'll get rid of those some other day. Adding a type to qapi/migration.json now recompiles some 120 instead of 2300 out of 5100 objects. Signed-off-by: Markus Armbruster <armbru@redhat.com> Message-Id: <20180211093607.27351-25-armbru@redhat.com> [eblake: rebase to master] Signed-off-by: Eric Blake <eblake@redhat.com>
2018-02-09Include qapi/error.h exactly where neededMarkus Armbruster
This cleanup makes the number of objects depending on qapi/error.h drop from 1910 (out of 4743) to 1612 in my "build everything" tree. While there, separate #include from file comment with a blank line, and drop a useless comment on why qemu/osdep.h is included first. Reviewed-by: Eric Blake <eblake@redhat.com> Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org> Signed-off-by: Markus Armbruster <armbru@redhat.com> Message-Id: <20180201111846.21846-5-armbru@redhat.com> [Semantic conflict with commit 34e304e975 resolved, OSX breakage fixed]
2017-12-19iothread: fix iothread_stop() race conditionStefan Hajnoczi
There is a small chance that iothread_stop() hangs as follows: Thread 3 (Thread 0x7f63eba5f700 (LWP 16105)): #0 0x00007f64012c09b6 in ppoll () at /lib64/libc.so.6 #1 0x000055959992eac9 in ppoll (__ss=0x0, __timeout=0x0, __nfds=<optimized out>, __fds=<optimized out>) at /usr/include/bits/poll2.h:77 #2 0x000055959992eac9 in qemu_poll_ns (fds=<optimized out>, nfds=<optimized out>, timeout=<optimized out>) at util/qemu-timer.c:322 #3 0x0000559599930711 in aio_poll (ctx=0x55959bdb83c0, blocking=blocking@entry=true) at util/aio-posix.c:629 #4 0x00005595996806fe in iothread_run (opaque=0x55959bd78400) at iothread.c:59 #5 0x00007f640159f609 in start_thread () at /lib64/libpthread.so.0 #6 0x00007f64012cce6f in clone () at /lib64/libc.so.6 Thread 1 (Thread 0x7f640b45b280 (LWP 16103)): #0 0x00007f64015a0b6d in pthread_join () at /lib64/libpthread.so.0 #1 0x00005595999332ef in qemu_thread_join (thread=<optimized out>) at util/qemu-thread-posix.c:547 #2 0x00005595996808ae in iothread_stop (iothread=<optimized out>) at iothread.c:91 #3 0x000055959968094d in iothread_stop_iter (object=<optimized out>, opaque=<optimized out>) at iothread.c:102 #4 0x0000559599857d97 in do_object_child_foreach (obj=obj@entry=0x55959bdb8100, fn=fn@entry=0x559599680930 <iothread_stop_iter>, opaque=opaque@entry=0x0, recurse=recurse@entry=false) at qom/object.c:852 #5 0x0000559599859477 in object_child_foreach (obj=obj@entry=0x55959bdb8100, fn=fn@entry=0x559599680930 <iothread_stop_iter>, opaque=opaque@entry=0x0) at qom/object.c:867 #6 0x0000559599680a6e in iothread_stop_all () at iothread.c:341 #7 0x000055959955b1d5 in main (argc=<optimized out>, argv=<optimized out>, envp=<optimized out>) at vl.c:4913 The relevant code from iothread_run() is: while (!atomic_read(&iothread->stopping)) { aio_poll(iothread->ctx, true); and iothread_stop(): iothread->stopping = true; aio_notify(iothread->ctx); ... qemu_thread_join(&iothread->thread); The following scenario can occur: 1. IOThread: while (!atomic_read(&iothread->stopping)) -> stopping=false 2. Main loop: iothread->stopping = true; aio_notify(iothread->ctx); 3. IOThread: aio_poll(iothread->ctx, true); -> hang The bug is explained by the AioContext->notify_me doc comments: "If this field is 0, everything (file descriptors, bottom halves, timers) will be re-evaluated before the next blocking poll(), thus the event_notifier_set call can be skipped." The problem is that "everything" does not include checking iothread->stopping. This means iothread_run() will block in aio_poll() if aio_notify() was called just before aio_poll(). This patch fixes the hang by replacing aio_notify() with aio_bh_schedule_oneshot(). This makes aio_poll() or g_main_loop_run() to return. Implementing this properly required a new bool running flag. The new flag prevents races that are tricky if we try to use iothread->stopping. Now iothread->stopping is purely for iothread_stop() and iothread->running is purely for the iothread_run() thread. Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com> Reviewed-by: Eric Blake <eblake@redhat.com> Message-id: 20171207201320.19284-6-stefanha@redhat.com Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2017-12-19iothread: add iothread_by_id() APIStefan Hajnoczi
Encapsulate IOThread QOM object lookup so that callers don't need to know how and where IOThread objects live. Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com> Reviewed-by: Kevin Wolf <kwolf@redhat.com> Reviewed-by: Eric Blake <eblake@redhat.com> Message-id: 20171206144550.22295-8-stefanha@redhat.com Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2017-10-03iothread: delay the context release to finalizePeter Xu
When gcontext is used with iothread, the context will be destroyed during iothread_stop(). That's not good since sometimes we would like to keep the resources until iothread is destroyed, but we may want to stop the thread before that point. Delay the destruction of gcontext to iothread finalize. Then we can do: iothread_stop(thread); some_cleanup_on_resources(); iothread_destroy(thread); We may need this patch if we want to run chardev IOs in iothreads and hopefully clean them up correctly. For more specific information, please see 2b316774f6 ("qemu-char: do not operate on sources from finalize callbacks"). Reviewed-by: Fam Zheng <famz@redhat.com> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com> Signed-off-by: Peter Xu <peterx@redhat.com> Message-id: 20170928025958.1420-5-peterx@redhat.com Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2017-10-03iothread: export iothread_stop()Peter Xu
So that internal iothread users can explicitly stop one iothread without destroying it. Since at it, fix iothread_stop() to allow it to be called multiple times. Before this patch we may call iothread_stop() more than once on single iothread, while that may not be correct since qemu_thread_join() is not allowed to run twice. From manual of pthread_join(): Joining with a thread that has previously been joined results in undefined behavior. Reviewed-by: Fam Zheng <famz@redhat.com> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com> Signed-off-by: Peter Xu <peterx@redhat.com> Message-id: 20170928025958.1420-4-peterx@redhat.com Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2017-10-03iothread: provide helpers for internal usePeter Xu
IOThread is a general framework that contains IO loop environment and a real thread behind. It's also good to be used internally inside qemu. Provide some helpers for it to create iothreads to be used internally. Put all the internal used iothreads into the internal object container. Reviewed-by: Fam Zheng <famz@redhat.com> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com> Signed-off-by: Peter Xu <peterx@redhat.com> Message-id: 20170928025958.1420-3-peterx@redhat.com Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2017-09-29iothread: Make iothread_stop() idempotentEduardo Habkost
Currently, iothread_stop_all() makes all iothread objects unsafe to be destroyed, because qemu_thread_join() ends up being called twice. To fix this, make iothread_stop() idempotent by checking thread->stopped. Fixes the following crash: qemu-system-x86_64 -object iothread,id=iothread0 -monitor stdio -display none QEMU 2.10.50 monitor - type 'help' for more information (qemu) quit qemu: qemu_thread_join: No such process Aborted (core dumped) Reported-by: Christian Borntraeger <borntraeger@de.ibm.com> Signed-off-by: Eduardo Habkost <ehabkost@redhat.com> Message-Id: <20170926130028.12471-1-ehabkost@redhat.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2017-09-08qemu-iothread: IOThread supports the GMainContext event loopWang Yong
IOThread uses AioContext event loop and does not run a GMainContext. Therefore,chardev cannot work in IOThread,such as the chardev is used for colo-compare packets reception. This patch makes the IOThread run the GMainContext event loop, chardev and IOThread can work together. Reviewed-by: Fam Zheng <famz@redhat.com> Signed-off-by: Wang Yong <wang.yong155@zte.com.cn> Signed-off-by: Wang Guang <wang.guang55@zte.com.cn> Signed-off-by: Jason Wang <jasowang@redhat.com>
2017-02-21monitor: add poll-* properties into query-iothreads resultPavel Hrdina
IOthreads were recently extended by new properties that can enable/disable and configure aio polling. This will also allow other tools that uses QEMU to probe for existence of those new properties via query-qmp-schema. Signed-off-by: Pavel Hrdina <phrdina@redhat.com> Message-Id: <3163c16d6ab4257f7be9ad44fe9cc0ce8c359e5a.1486718555.git.phrdina@redhat.com> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com> Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
2017-02-03iothread: enable AioContext polling by defaultStefan Hajnoczi
IOThread AioContexts are likely to consist only of event sources like virtqueue ioeventfds and LinuxAIO completion eventfds that are pollable from userspace (without system calls). We recently merged the AioContext polling feature but didn't enable it by default yet. I have gone back over the performance data on the mailing list and picked a default polling value that gave good results. Let's enable AioContext polling by default so users don't have another switch they need to set manually. If performance regressions are found we can still disable this for the QEMU 2.9 release. Cc: Paolo Bonzini <pbonzini@redhat.com> Cc: Christian Borntraeger <borntraeger@de.ibm.com> Cc: Karl Rister <krister@redhat.com> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com> Message-id: 20170126170119.27876-1-stefanha@redhat.com Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2017-01-03iothread: add poll-grow and poll-shrink parametersStefan Hajnoczi
These parameters control the poll time self-tuning algorithm. They are optional and will default to sane values if omitted. Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com> Reviewed-by: Paolo Bonzini <pbonzini@redhat.com> Message-id: 20161201192652.9509-14-stefanha@redhat.com Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2017-01-03aio: self-tune polling timeStefan Hajnoczi
This patch is based on the algorithm for the kvm.ko halt_poll_ns parameter in Linux. The initial polling time is zero. If the event loop is woken up within the maximum polling time it means polling could be effective, so grow polling time. If the event loop is woken up beyond the maximum polling time it means polling is not effective, so shrink polling time. If the event loop makes progress within the current polling time then the sweet spot has been reached. This algorithm adjusts the polling time so it can adapt to variations in workloads. The goal is to reach the sweet spot while also recognizing when polling would hurt more than help. Two new trace events, poll_grow and poll_shrink, are added for observing polling time adjustment. Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com> Reviewed-by: Paolo Bonzini <pbonzini@redhat.com> Message-id: 20161201192652.9509-13-stefanha@redhat.com Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2017-01-03iothread: add polling parametersStefan Hajnoczi
Poll mode can be configured with -object iothread,poll-max-ns=NUM. Polling is disabled with a value of 0 nanoseconds. Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com> Reviewed-by: Paolo Bonzini <pbonzini@redhat.com> Message-id: 20161201192652.9509-7-stefanha@redhat.com Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2016-10-28iothread: release AioContext around aio_pollPaolo Bonzini
This is the first step towards having fine-grained critical sections in dataplane threads, which will resolve lock ordering problems between address_space_* functions (which need the BQL when doing MMIO, even after we complete RCU-based dispatch) and the AioContext. Because AioContext does not use contention callbacks anymore, the unit test has to be changed. Previously applied as a0710f7995f914e3044e5899bd8ff6c43c62f916 and then reverted. Reviewed-by: Fam Zheng <famz@redhat.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Message-Id: <1477565348-5458-19-git-send-email-pbonzini@redhat.com> Signed-off-by: Fam Zheng <famz@redhat.com>
2016-10-28iothread: detach all block devices before stopping themPaolo Bonzini
Soon bdrv_drain will not call aio_poll itself on iothreads. If block devices are left hanging off the iothread's AioContext, there will be no one to do I/O for those poor devices. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Reviewed-by: Fam Zheng <famz@redhat.com> Message-Id: <1477565348-5458-13-git-send-email-pbonzini@redhat.com> Signed-off-by: Fam Zheng <famz@redhat.com>
2016-10-28aio: introduce qemu_get_current_aio_contextPaolo Bonzini
This will be used by BDRV_POLL_WHILE (and thus by bdrv_drain) to choose how to wait for I/O completion. Reviewed-by: Fam Zheng <famz@redhat.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Message-Id: <1477565348-5458-12-git-send-email-pbonzini@redhat.com> Signed-off-by: Fam Zheng <famz@redhat.com>
2016-09-28iothread: check iothread->ctx before aio_context_unref to avoid assertionLin Ma
if iothread->ctx is set to NULL, aio_context_unref triggers the assertion: g_source_unref: assertion 'source != NULL' failed. The patch fixes it. Signed-off-by: Lin Ma <lma@suse.com> Reviewed-by: Paolo Bonzini <pbonzini@redhat.com> Message-id: 20160926052958.10716-1-lma@suse.com Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2016-09-13iothread: Stop threads before main() quitsFam Zheng
Right after main_loop ends, we release various things but keep iothread alive. The latter is not prepared to the sudden change of resources. Specifically, after bdrv_close_all(), virtio-scsi dataplane get a surprise at the empty BlockBackend: (gdb) bt at /usr/src/debug/qemu-2.6.0/hw/scsi/virtio-scsi.c:543 at /usr/src/debug/qemu-2.6.0/hw/scsi/virtio-scsi.c:577 It is because the d->conf.blk->root is set to NULL, then blk_get_aio_context() returns qemu_aio_context, whereas s->ctx is still pointing to the iothread: hw/scsi/virtio-scsi.c:543: if (s->dataplane_started) { assert(blk_get_aio_context(d->conf.blk) == s->ctx); } To fix this, let's stop iothreads before doing bdrv_close_all(). Cc: qemu-stable@nongnu.org Signed-off-by: Fam Zheng <famz@redhat.com> Reviewed-by: Paolo Bonzini <pbonzini@redhat.com> Message-id: 1473326931-9699-1-git-send-email-famz@redhat.com Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2016-02-04all: Clean up includesPeter Maydell
Clean up includes so that osdep.h is included first and headers which it implies are not included manually. This commit was created with scripts/clean-includes. Signed-off-by: Peter Maydell <peter.maydell@linaro.org> Message-id: 1454089805-5470-16-git-send-email-peter.maydell@linaro.org
2015-12-03iothread: include id in thread namePaolo Bonzini
This makes it easier to find the desired thread. Use "IO" plus the id; even with the 14 character limit on the thread name, enough of the id should be readable (e.g. "IO iothreadNNN" with three characters for the number). Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com> Message-id: 1448372804-5034-1-git-send-email-pbonzini@redhat.com Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2015-07-24rcu: actually register threads that have RCU read-side critical sectionsPaolo Bonzini
Otherwise, grace periods are detected too early! Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2015-06-19qom: Add helper function for getting user objects rootDaniel P. Berrange
Add object_get_objects_root() function which is a convenience for obtaining the Object * located at /objects in the object composition tree. Convert existing code over to use the new API where appropriate. Signed-off-by: Daniel P. Berrange <berrange@redhat.com> Reviewed-by: Eric Blake <eblake@redhat.com> Signed-off-by: Andreas Färber <afaerber@suse.de>
2015-06-12Revert "iothread: release iothread around aio_poll"Stefan Hajnoczi
This reverts commit a0710f7995f914e3044e5899bd8ff6c43c62f916. In qemu-devel email message <556DBF87.2020908@de.ibm.com>, Christian Borntraeger writes: Having many guests all with a kernel/ramdisk (via -kernel) and several null block devices will result in hangs. All hanging guests are in partition detection code waiting for an I/O to return so very early maybe even the first I/O. Reverting that commit "fixes" the hangs. Reverting this commit for the 2.4 release. More time is needed to investigate and correct this patch. Reported-by: Christian Borntraeger <borntraeger@de.ibm.com> Suggested-by: Paolo Bonzini <pbonzini@redhat.com> Reviewed-by: Fam Zheng <famz@redhat.com> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2015-05-08Remove various unused functionsThomas Huth
The functions tpm_backend_thread_tpm_reset() and iothread_find() are completely unused, let's remove them. Signed-off-by: Thomas Huth <huth@tuxfamily.org> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com> Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
2015-04-28iothread: release iothread around aio_pollPaolo Bonzini
This is the first step towards having fine-grained critical sections in dataplane threads, which resolves lock ordering problems between address_space_* functions (which need the BQL when doing MMIO, even after we complete RCU-based dispatch) and the AioContext. Because AioContext does not use contention callbacks anymore, the unit test has to be changed. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com> Message-id: 1424449612-18215-4-git-send-email-pbonzini@redhat.com Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2014-09-22async: aio_context_new(): Handle event_notifier_init failureChrysostomos Nanakos
On a system with a low limit of open files the initialization of the event notifier could fail and QEMU exits without printing any error information to the user. The problem can be easily reproduced by enforcing a low limit of open files and start QEMU with enough I/O threads to hit this limit. The same problem raises, without the creation of I/O threads, while QEMU initializes the main event loop by enforcing an even lower limit of open files. This commit adds an error message on failure: # qemu [...] -object iothread,id=iothread0 -object iothread,id=iothread1 qemu: Failed to initialize event notifier: Too many open files in system Signed-off-by: Chrysostomos Nanakos <cnanakos@grnet.gr> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2014-07-14AioContext: do not rely on aio_poll(ctx, true) result to end a loopPaolo Bonzini
Currently, whenever aio_poll(ctx, true) has completed all pending work it returns true *and* the next call to aio_poll(ctx, true) will not block. This invariant has its roots in qemu_aio_flush()'s implementation as "while (qemu_aio_wait()) {}". However, qemu_aio_flush() does not exist anymore and bdrv_drain_all() is implemented differently; and this invariant is complicated to maintain and subtly different from the return value of GMainLoop's g_main_context_iteration. All calls to aio_poll(ctx, true) except one are guarded by a while() loop checking for a request to be incomplete, or a BlockDriverState to be idle. The one remaining call (in iothread.c) uses this to delay the aio_context_release/acquire pair until the AioContext is quiescent, however: - we can do the same just by using non-blocking aio_poll, similar to how vl.c invokes main_loop_wait - it is buggy, because it does not ensure that the AioContext is released between an aio_notify and the next time the iothread goes to sleep. This leads to hangs when stopping the dataplane thread. In the end, these semantics are a bad match for the current users of AioContext. So modify that one exception in iothread.c, which also fixes the hangs, as well as the testcase so that it use the same idiom as the actual QEMU code. Reported-by: Christian Borntraeger <borntraeger@de.ibm.com> Tested-by: Christian Borntraeger <borntraeger@de.ibm.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2014-04-04iothread: make IOThread struct definition publicStefan Hajnoczi
Make the IOThread struct definition public so objects can be embedded in parent structs. Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com> Reviewed-by: Paolo Bonzini <pbonzini@redhat.com> Tested-by: Christian Borntraeger <borntraeger@de.ibm.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2014-03-13qmp: add query-iothreads commandStefan Hajnoczi
The "query-iothreads" command returns a list of information about iothreads. See the patch for API documentation. Reviewed-by: Eric Blake <eblake@redhat.com> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2014-03-13iothread: stash thread ID awayStefan Hajnoczi
Keep the thread ID around so we can report it via QMP. There's only one problem: qemu_get_thread_id() (gettid() wrapper on Linux) must be called from the thread itself. There is no way to get the thread ID outside the thread. This patch uses a condvar to wait for iothread_run() to populate the thread_id inside the thread. Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2014-03-13iothread: add I/O thread objectStefan Hajnoczi
This is a stand-in for Michael Roth's QContext. I expect this to be replaced once QContext is completed. The IOThread object is an AioContext event loop thread. This patch adds the concept of multiple event loop threads, allowing users to define them. When SMP guests run on SMP hosts it makes sense to instantiate multiple IOThreads. This spreads event loop processing across multiple cores. Note that additional patches are required to actually bind a device to an IOThread. [Andreas Färber <afaerber@suse.de> pointed out that the embedded parent object instance should be called "parent_obj" and have a newline afterwards. This patch has been changed to reflect this. -- Stefan] Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>