Markus Armbruster <arm...@redhat.com> writes:
> From: Kevin Wolf <kw...@redhat.com>
>
> This moves the QMP dispatcher to a coroutine and runs all QMP command
> handlers that declare 'coroutine': true in coroutine context so they
> can avoid blocking the main loop while doing I/O or waiting for other
> events.
This subtly changes the replay behaviour leading to a hang in:
10:55:18 [alex.bennee@hackbox2:~/l/q/b/bisect] (625581c2…)|✚1(+1/-1) +
./tests/venv/bin/avocado run
tests/acceptance/replay_kernel.py:ReplayKernel.test_arm_virt
Fetching asset from
tests/acceptance/replay_kernel.py:ReplayKernel.test_arm_virt
JOB ID : ec11fd2544f06e6c0d421f16afa757b49f7ed734
JOB LOG :
/home/alex.bennee/avocado/job-results/job-2020-10-12T11.40-ec11fd2/job.log
(1/1) tests/acceptance/replay_kernel.py:ReplayKernel.test_arm_virt: ERROR:
Could not perform graceful shutdown (26.27 s)
RESULTS : PASS 0 | ERROR 1 | FAIL 0 | SKIP 0 | WARN 0 | INTERRUPT 0 |
CANCEL 0
JOB TIME : 27.77 s
Looking at the log:
2020-10-12 11:40:31,426 __init__ L0085 DEBUG| [ 3.887411]
rtc-pl031 9010000.pl031: setting system clock to 2020-10-12 10:40:31 UTC
(1602499231)
2020-10-12 11:40:31,428 __init__ L0085 DEBUG| [ 3.887431] sr_init:
No PMIC hook to init smartreflex
2020-10-12 11:40:31,447 __init__ L0085 DEBUG| [ 3.897193]
uart-pl011 9000000.pl011: no DMA platform data
2020-10-12 11:40:31,460 __init__ L0085 DEBUG| [ 3.897242] md:
Waiting for all devices to be available before autodetect
2020-10-12 11:40:31,462 __init__ L0085 DEBUG| [ 3.897259] md: If
you don't use raid, use raid=noautodetect
2020-10-12 11:40:31,475 __init__ L0085 DEBUG| [ 3.897819] md:
Autodetecting RAID arrays.
2020-10-12 11:40:31,476 __init__ L0085 DEBUG| [ 3.897832] md:
autorun ...
2020-10-12 11:40:31,477 __init__ L0085 DEBUG| [ 3.897842] md: ...
autorun DONE.
2020-10-12 11:40:31,483 __init__ L0085 DEBUG| [ 3.897962] VFS:
Cannot open root device "(null)" or unknown-block(0,0): error -6
2020-10-12 11:40:31,483 qmp L0245 DEBUG| >>> {'execute': 'quit'}
2020-10-12 11:40:31,495 qmp L0145 DEBUG| <<< {'timestamp':
{'seconds': 1602499231, 'microseconds': 493379}, 'event': 'SHUTDOWN', 'data':
{'guest': True, 'reason': 'guest-reset'}}
2020-10-12 11:40:31,733 machine L0325 WARNI| qemu received signal 6;
command: "./qemu-system-arm -display none -vga none -chardev
socket,id=mon,path=/var/tmp/tmpzls53khe/qemu-8487-monitor.sock -mon
chardev=mon,mode=control -machine virt -chardev
socket,id=console,path=/var/tmp/tmpzls53khe/qemu-8487-console.sock,server,nowait
-serial chardev:console -icount
shift=1,rr=record,rrfile=/var/tmp/avocado_n00stdrf/avocado_job_aw60qdul/1-tests_acceptance_replay_kernel.py_ReplayKernel.test_arm_virt/replay.bin
-kernel
/home/alex.bennee/avocado/data/cache/by_location/62750ce9e069e69e6a7ff04ff54c382ee660b92a/vmlinuz
-append printk.time=1 panic=-1 console=ttyAMA0 -net none -no-reboot"
2020-10-12 11:40:31,734 stacktrace L0039 ERROR|
2020-10-12 11:40:31,734 stacktrace L0042 ERROR| Reproduced traceback
from:
/home/alex.bennee/lsrc/qemu.git/builds/bisect/tests/venv/lib/python3.6/site-packages/avocado/core/test.py:767
2020-10-12 11:40:31,735 stacktrace L0045 ERROR| Traceback (most recent
call last):
2020-10-12 11:40:31,735 stacktrace L0045 ERROR| File
"/home/alex.bennee/lsrc/qemu.git/python/qemu/machine.py", line 435, in
_do_shutdown
2020-10-12 11:40:31,735 stacktrace L0045 ERROR|
self._soft_shutdown(timeout, has_quit)
2020-10-12 11:40:31,735 stacktrace L0045 ERROR| File
"/home/alex.bennee/lsrc/qemu.git/python/qemu/machine.py", line 415, in
_soft_shutdown
2020-10-12 11:40:31,735 stacktrace L0045 ERROR|
self._qmp.cmd('quit')
2020-10-12 11:40:31,735 stacktrace L0045 ERROR| File
"/home/alex.bennee/lsrc/qemu.git/python/qemu/qmp.py", line 266, in cmd
2020-10-12 11:40:31,735 stacktrace L0045 ERROR| return
self.cmd_obj(qmp_cmd)
2020-10-12 11:40:31,735 stacktrace L0045 ERROR| File
"/home/alex.bennee/lsrc/qemu.git/python/qemu/qmp.py", line 249, in cmd_obj
2020-10-12 11:40:31,736 stacktrace L0045 ERROR| raise
QMPConnectError("Unexpected empty reply from server")
2020-10-12 11:40:31,736 stacktrace L0045 ERROR|
qemu.qmp.QMPConnectError: Unexpected empty reply from server
2020-10-12 11:40:31,736 stacktrace L0045 ERROR|
2020-10-12 11:40:31,736 stacktrace L0045 ERROR| The above exception was
the direct cause of the following exception:
2020-10-12 11:40:31,736 stacktrace L0045 ERROR|
2020-10-12 11:40:31,736 stacktrace L0045 ERROR| Traceback (most recent
call last):
2020-10-12 11:40:31,736 stacktrace L0045 ERROR| File
"/home/alex.bennee/lsrc/qemu.git/builds/bisect/tests/acceptance/replay_kernel.py",
line 128, in test_arm_virt
2020-10-12 11:40:31,736 stacktrace L0045 ERROR|
self.run_rr(kernel_path, kernel_command_line, console_pattern, shift=1)
2020-10-12 11:40:31,736 stacktrace L0045 ERROR| File
"/home/alex.bennee/lsrc/qemu.git/builds/bisect/tests/acceptance/replay_kernel.py",
line 71, in run_rr
2020-10-12 11:40:31,736 stacktrace L0045 ERROR| True, shift, args,
replay_path)
2020-10-12 11:40:31,736 stacktrace L0045 ERROR| File
"/home/alex.bennee/lsrc/qemu.git/builds/bisect/tests/acceptance/replay_kernel.py",
line 57, in run_vm
2020-10-12 11:40:31,736 stacktrace L0045 ERROR| vm.shutdown()
2020-10-12 11:40:31,736 stacktrace L0045 ERROR| File
"/home/alex.bennee/lsrc/qemu.git/python/qemu/machine.py", line 465, in shutdown
2020-10-12 11:40:31,736 stacktrace L0045 ERROR|
self._do_shutdown(timeout, has_quit)
2020-10-12 11:40:31,736 stacktrace L0045 ERROR| File
"/home/alex.bennee/lsrc/qemu.git/python/qemu/machine.py", line 439, in
_do_shutdown
2020-10-12 11:40:31,736 stacktrace L0045 ERROR| from exc
2020-10-12 11:40:31,737 stacktrace L0045 ERROR|
qemu.machine.AbnormalShutdown: Could not perform graceful shutdown
The commit before:
2020-10-12 11:44:02,803 __init__ L0085 DEBUG| [ 3.897837] md: ...
autorun DONE.
2020-10-12 11:44:02,806 __init__ L0085 DEBUG| [ 3.897958] VFS:
Cannot open root device "(null)" or unknown-block(0,0): error -6
2020-10-12 11:44:02,806 qmp L0245 DEBUG| >>> {'execute': 'quit'}
2020-10-12 11:44:02,814 qmp L0250 DEBUG| <<< {'return': {}}
2020-10-12 11:44:02,879 replay_kernel L0059 INFO | finished the recording
with log size 237596 bytes
2020-10-12 11:44:02,879 replay_kernel L0064 INFO | elapsed time 24.35 sec
2020-10-12 11:44:02,888 replay_kernel L0044 INFO | replaying the
execution...
2020-10-12 11:44:02,889 machine L0362 DEBUG| VM launch command:
'./qemu-system-arm -display none -vga none -chardev
socket,id=mon,path=/var/tmp/tmpihqswp6_/qemu-7747-monitor.sock -mon
chardev=mon,mode=control -machine virt -chardev
socket,id=console,path=/var/tmp/tmpihqswp6_/qemu-7747-console.sock,server,nowait
-serial chardev:console
-icount
shift=1,rr=replay,rrfile=/var/tmp/avocado_o3pfy2he/avocado_job_nf30vjqg/1-tests_acceptance_replay_kernel.py_ReplayKernel.test_arm_virt/replay.bin
-kernel
/home/alex.bennee/avocado/data/cache/by_location/62750ce9e069e69e6a7ff04ff54c382ee660b92a/vmlinuz
-append printk.time=1 panic=-1 console=ttyAMA0 -net none -no-reboot'
2020-10-12 11:44:03,001 qmp L0245 DEBUG| >>> {'execute':
'qmp_capabilities'}
2020-10-12 11:44:03,172 qmp L0250 DEBUG| <<< {'return': {}}
2020-10-12 11:44:04,899 __init__ L0085 DEBUG| [ 0.000000] Booting
Linux on physical CPU 0x0
2020-10-12 11:44:04,904 __init__ L0085 DEBUG| [ 0.000000] Linux
version 4.18.16-300.fc29.armv7hl
(mockbu...@buildvm-armv7-06.arm.fedoraproject.org) (gcc version 8.2.1 20180801
(Red Hat 8.2.1-2) (GCC)) #1 SMP Sun Oct 21 00:56:28 UTC 2018
>
> For commands that are not declared safe to run in a coroutine, the
> dispatcher drops out of coroutine context by calling the QMP command
> handler from a bottom half.
>
> Signed-off-by: Kevin Wolf <kw...@redhat.com>
> Reviewed-by: Markus Armbruster <arm...@redhat.com>
> Message-Id: <20201005155855.256490-10-kw...@redhat.com>
> Reviewed-by: Markus Armbruster <arm...@redhat.com>
> Reviewed-by: Stefan Hajnoczi <stefa...@redhat.com>
> Signed-off-by: Markus Armbruster <arm...@redhat.com>
> ---
> include/qapi/qmp/dispatch.h | 1 +
> monitor/monitor-internal.h | 6 +-
> monitor/monitor.c | 55 +++++++++++++---
> monitor/qmp.c | 122 +++++++++++++++++++++++++++---------
> qapi/qmp-dispatch.c | 63 +++++++++++++++++--
> qapi/qmp-registry.c | 3 +
> util/aio-posix.c | 8 ++-
> 7 files changed, 213 insertions(+), 45 deletions(-)
>
> diff --git a/include/qapi/qmp/dispatch.h b/include/qapi/qmp/dispatch.h
> index 9fd2b720a7..af8d96c570 100644
> --- a/include/qapi/qmp/dispatch.h
> +++ b/include/qapi/qmp/dispatch.h
> @@ -31,6 +31,7 @@ typedef enum QmpCommandOptions
> typedef struct QmpCommand
> {
> const char *name;
> + /* Runs in coroutine context if QCO_COROUTINE is set */
> QmpCommandFunc *fn;
> QmpCommandOptions options;
> QTAILQ_ENTRY(QmpCommand) node;
> diff --git a/monitor/monitor-internal.h b/monitor/monitor-internal.h
> index b39e03b744..b55d6df07f 100644
> --- a/monitor/monitor-internal.h
> +++ b/monitor/monitor-internal.h
> @@ -155,7 +155,9 @@ static inline bool monitor_is_qmp(const Monitor *mon)
>
> typedef QTAILQ_HEAD(MonitorList, Monitor) MonitorList;
> extern IOThread *mon_iothread;
> -extern QEMUBH *qmp_dispatcher_bh;
> +extern Coroutine *qmp_dispatcher_co;
> +extern bool qmp_dispatcher_co_shutdown;
> +extern bool qmp_dispatcher_co_busy;
> extern QmpCommandList qmp_commands, qmp_cap_negotiation_commands;
> extern QemuMutex monitor_lock;
> extern MonitorList mon_list;
> @@ -173,7 +175,7 @@ void monitor_fdsets_cleanup(void);
>
> void qmp_send_response(MonitorQMP *mon, const QDict *rsp);
> void monitor_data_destroy_qmp(MonitorQMP *mon);
> -void monitor_qmp_bh_dispatcher(void *data);
> +void coroutine_fn monitor_qmp_dispatcher_co(void *data);
>
> int get_monitor_def(int64_t *pval, const char *name);
> void help_cmd(Monitor *mon, const char *name);
> diff --git a/monitor/monitor.c b/monitor/monitor.c
> index ef68ca9d21..ceffe1a83b 100644
> --- a/monitor/monitor.c
> +++ b/monitor/monitor.c
> @@ -55,8 +55,32 @@ typedef struct {
> /* Shared monitor I/O thread */
> IOThread *mon_iothread;
>
> -/* Bottom half to dispatch the requests received from I/O thread */
> -QEMUBH *qmp_dispatcher_bh;
> +/* Coroutine to dispatch the requests received from I/O thread */
> +Coroutine *qmp_dispatcher_co;
> +
> +/* Set to true when the dispatcher coroutine should terminate */
> +bool qmp_dispatcher_co_shutdown;
> +
> +/*
> + * qmp_dispatcher_co_busy is used for synchronisation between the
> + * monitor thread and the main thread to ensure that the dispatcher
> + * coroutine never gets scheduled a second time when it's already
> + * scheduled (scheduling the same coroutine twice is forbidden).
> + *
> + * It is true if the coroutine is active and processing requests.
> + * Additional requests may then be pushed onto mon->qmp_requests,
> + * and @qmp_dispatcher_co_shutdown may be set without further ado.
> + * @qmp_dispatcher_co_busy must not be woken up in this case.
> + *
> + * If false, you also have to set @qmp_dispatcher_co_busy to true and
> + * wake up @qmp_dispatcher_co after pushing the new requests.
> + *
> + * The coroutine will automatically change this variable back to false
> + * before it yields. Nobody else may set the variable to false.
> + *
> + * Access must be atomic for thread safety.
> + */
> +bool qmp_dispatcher_co_busy;
>
> /*
> * Protects mon_list, monitor_qapi_event_state, coroutine_mon,
> @@ -623,9 +647,24 @@ void monitor_cleanup(void)
> }
> qemu_mutex_unlock(&monitor_lock);
>
> - /* QEMUBHs needs to be deleted before destroying the I/O thread */
> - qemu_bh_delete(qmp_dispatcher_bh);
> - qmp_dispatcher_bh = NULL;
> + /*
> + * The dispatcher needs to stop before destroying the I/O thread.
> + *
> + * We need to poll both qemu_aio_context and iohandler_ctx to make
> + * sure that the dispatcher coroutine keeps making progress and
> + * eventually terminates. qemu_aio_context is automatically
> + * polled by calling AIO_WAIT_WHILE on it, but we must poll
> + * iohandler_ctx manually.
> + */
> + qmp_dispatcher_co_shutdown = true;
> + if (!qatomic_xchg(&qmp_dispatcher_co_busy, true)) {
> + aio_co_wake(qmp_dispatcher_co);
> + }
> +
> + AIO_WAIT_WHILE(qemu_get_aio_context(),
> + (aio_poll(iohandler_get_aio_context(), false),
> + qatomic_mb_read(&qmp_dispatcher_co_busy)));
> +
> if (mon_iothread) {
> iothread_destroy(mon_iothread);
> mon_iothread = NULL;
> @@ -649,9 +688,9 @@ void monitor_init_globals_core(void)
> * have commands assuming that context. It would be nice to get
> * rid of those assumptions.
> */
> - qmp_dispatcher_bh = aio_bh_new(iohandler_get_aio_context(),
> - monitor_qmp_bh_dispatcher,
> - NULL);
> + qmp_dispatcher_co = qemu_coroutine_create(monitor_qmp_dispatcher_co,
> NULL);
> + qatomic_mb_set(&qmp_dispatcher_co_busy, true);
> + aio_co_schedule(iohandler_get_aio_context(), qmp_dispatcher_co);
> }
>
> int monitor_init(MonitorOptions *opts, bool allow_hmp, Error **errp)
> diff --git a/monitor/qmp.c b/monitor/qmp.c
> index e746b3575d..b42f8c6af3 100644
> --- a/monitor/qmp.c
> +++ b/monitor/qmp.c
> @@ -133,6 +133,10 @@ static void monitor_qmp_respond(MonitorQMP *mon, QDict
> *rsp)
> }
> }
>
> +/*
> + * Runs outside of coroutine context for OOB commands, but in
> + * coroutine context for everything else.
> + */
> static void monitor_qmp_dispatch(MonitorQMP *mon, QObject *req)
> {
> QDict *rsp;
> @@ -206,43 +210,99 @@ static QMPRequest
> *monitor_qmp_requests_pop_any_with_lock(void)
> return req_obj;
> }
>
> -void monitor_qmp_bh_dispatcher(void *data)
> +void coroutine_fn monitor_qmp_dispatcher_co(void *data)
> {
> - QMPRequest *req_obj = monitor_qmp_requests_pop_any_with_lock();
> + QMPRequest *req_obj = NULL;
> QDict *rsp;
> bool need_resume;
> MonitorQMP *mon;
>
> - if (!req_obj) {
> - return;
> - }
> + while (true) {
> + assert(qatomic_mb_read(&qmp_dispatcher_co_busy) == true);
>
> - mon = req_obj->mon;
> - /* qmp_oob_enabled() might change after "qmp_capabilities" */
> - need_resume = !qmp_oob_enabled(mon) ||
> - mon->qmp_requests->length == QMP_REQ_QUEUE_LEN_MAX - 1;
> - qemu_mutex_unlock(&mon->qmp_queue_lock);
> - if (req_obj->req) {
> - QDict *qdict = qobject_to(QDict, req_obj->req);
> - QObject *id = qdict ? qdict_get(qdict, "id") : NULL;
> - trace_monitor_qmp_cmd_in_band(qobject_get_try_str(id) ?: "");
> - monitor_qmp_dispatch(mon, req_obj->req);
> - } else {
> - assert(req_obj->err);
> - rsp = qmp_error_response(req_obj->err);
> - req_obj->err = NULL;
> - monitor_qmp_respond(mon, rsp);
> - qobject_unref(rsp);
> - }
> + /*
> + * Mark the dispatcher as not busy already here so that we
> + * don't miss any new requests coming in the middle of our
> + * processing.
> + */
> + qatomic_mb_set(&qmp_dispatcher_co_busy, false);
>
> - if (need_resume) {
> - /* Pairs with the monitor_suspend() in handle_qmp_command() */
> - monitor_resume(&mon->common);
> - }
> - qmp_request_free(req_obj);
> + while (!(req_obj = monitor_qmp_requests_pop_any_with_lock())) {
> + /*
> + * No more requests to process. Wait to be reentered from
> + * handle_qmp_command() when it pushes more requests, or
> + * from monitor_cleanup() when it requests shutdown.
> + */
> + if (!qmp_dispatcher_co_shutdown) {
> + qemu_coroutine_yield();
>
> - /* Reschedule instead of looping so the main loop stays responsive */
> - qemu_bh_schedule(qmp_dispatcher_bh);
> + /*
> + * busy must be set to true again by whoever
> + * rescheduled us to avoid double scheduling
> + */
> + assert(qatomic_xchg(&qmp_dispatcher_co_busy, false) == true);
> + }
> +
> + /*
> + * qmp_dispatcher_co_shutdown may have changed if we
> + * yielded and were reentered from monitor_cleanup()
> + */
> + if (qmp_dispatcher_co_shutdown) {
> + return;
> + }
> + }
> +
> + if (qatomic_xchg(&qmp_dispatcher_co_busy, true) == true) {
> + /*
> + * Someone rescheduled us (probably because a new requests
> + * came in), but we didn't actually yield. Do that now,
> + * only to be immediately reentered and removed from the
> + * list of scheduled coroutines.
> + */
> + qemu_coroutine_yield();
> + }
> +
> + /*
> + * Move the coroutine from iohandler_ctx to qemu_aio_context for
> + * executing the command handler so that it can make progress if it
> + * involves an AIO_WAIT_WHILE().
> + */
> + aio_co_schedule(qemu_get_aio_context(), qmp_dispatcher_co);
> + qemu_coroutine_yield();
> +
> + mon = req_obj->mon;
> + /* qmp_oob_enabled() might change after "qmp_capabilities" */
> + need_resume = !qmp_oob_enabled(mon) ||
> + mon->qmp_requests->length == QMP_REQ_QUEUE_LEN_MAX - 1;
> + qemu_mutex_unlock(&mon->qmp_queue_lock);
> + if (req_obj->req) {
> + QDict *qdict = qobject_to(QDict, req_obj->req);
> + QObject *id = qdict ? qdict_get(qdict, "id") : NULL;
> + trace_monitor_qmp_cmd_in_band(qobject_get_try_str(id) ?: "");
> + monitor_qmp_dispatch(mon, req_obj->req);
> + } else {
> + assert(req_obj->err);
> + rsp = qmp_error_response(req_obj->err);
> + req_obj->err = NULL;
> + monitor_qmp_respond(mon, rsp);
> + qobject_unref(rsp);
> + }
> +
> + if (need_resume) {
> + /* Pairs with the monitor_suspend() in handle_qmp_command() */
> + monitor_resume(&mon->common);
> + }
> + qmp_request_free(req_obj);
> +
> + /*
> + * Yield and reschedule so the main loop stays responsive.
> + *
> + * Move back to iohandler_ctx so that nested event loops for
> + * qemu_aio_context don't start new monitor commands.
> + */
> + aio_co_schedule(iohandler_get_aio_context(), qmp_dispatcher_co);
> + qemu_coroutine_yield();
> + }
> }
>
> static void handle_qmp_command(void *opaque, QObject *req, Error *err)
> @@ -303,7 +363,9 @@ static void handle_qmp_command(void *opaque, QObject
> *req, Error *err)
> qemu_mutex_unlock(&mon->qmp_queue_lock);
>
> /* Kick the dispatcher routine */
> - qemu_bh_schedule(qmp_dispatcher_bh);
> + if (!qatomic_xchg(&qmp_dispatcher_co_busy, true)) {
> + aio_co_wake(qmp_dispatcher_co);
> + }
> }
>
> static void monitor_qmp_read(void *opaque, const uint8_t *buf, int size)
> diff --git a/qapi/qmp-dispatch.c b/qapi/qmp-dispatch.c
> index 5677ba92ca..9a2d7dd29a 100644
> --- a/qapi/qmp-dispatch.c
> +++ b/qapi/qmp-dispatch.c
> @@ -12,12 +12,16 @@
> */
>
> #include "qemu/osdep.h"
> +
> +#include "block/aio.h"
> #include "qapi/error.h"
> #include "qapi/qmp/dispatch.h"
> #include "qapi/qmp/qdict.h"
> #include "qapi/qmp/qjson.h"
> #include "sysemu/runstate.h"
> #include "qapi/qmp/qbool.h"
> +#include "qemu/coroutine.h"
> +#include "qemu/main-loop.h"
>
> static QDict *qmp_dispatch_check_obj(QDict *dict, bool allow_oob,
> Error **errp)
> @@ -88,6 +92,30 @@ bool qmp_is_oob(const QDict *dict)
> && !qdict_haskey(dict, "execute");
> }
>
> +typedef struct QmpDispatchBH {
> + const QmpCommand *cmd;
> + Monitor *cur_mon;
> + QDict *args;
> + QObject **ret;
> + Error **errp;
> + Coroutine *co;
> +} QmpDispatchBH;
> +
> +static void do_qmp_dispatch_bh(void *opaque)
> +{
> + QmpDispatchBH *data = opaque;
> +
> + assert(monitor_cur() == NULL);
> + monitor_set_cur(qemu_coroutine_self(), data->cur_mon);
> + data->cmd->fn(data->args, data->ret, data->errp);
> + monitor_set_cur(qemu_coroutine_self(), NULL);
> + aio_co_wake(data->co);
> +}
> +
> +/*
> + * Runs outside of coroutine context for OOB commands, but in coroutine
> + * context for everything else.
> + */
> QDict *qmp_dispatch(const QmpCommandList *cmds, QObject *request,
> bool allow_oob, Monitor *cur_mon)
> {
> @@ -153,12 +181,39 @@ QDict *qmp_dispatch(const QmpCommandList *cmds, QObject
> *request,
> qobject_ref(args);
> }
>
> + assert(!(oob && qemu_in_coroutine()));
> assert(monitor_cur() == NULL);
> - monitor_set_cur(qemu_coroutine_self(), cur_mon);
> + if (!!(cmd->options & QCO_COROUTINE) == qemu_in_coroutine()) {
> + monitor_set_cur(qemu_coroutine_self(), cur_mon);
> + cmd->fn(args, &ret, &err);
> + monitor_set_cur(qemu_coroutine_self(), NULL);
> + } else {
> + /*
> + * Actual context doesn't match the one the command needs.
> + *
> + * Case 1: we are in coroutine context, but command does not
> + * have QCO_COROUTINE. We need to drop out of coroutine
> + * context for executing it.
> + *
> + * Case 2: we are outside coroutine context, but command has
> + * QCO_COROUTINE. Can't actually happen, because we get here
> + * outside coroutine context only when executing a command
> + * out of band, and OOB commands never have QCO_COROUTINE.
> + */
> + assert(!oob && qemu_in_coroutine() && !(cmd->options &
> QCO_COROUTINE));
>
> - cmd->fn(args, &ret, &err);
> -
> - monitor_set_cur(qemu_coroutine_self(), NULL);
> + QmpDispatchBH data = {
> + .cur_mon = cur_mon,
> + .cmd = cmd,
> + .args = args,
> + .ret = &ret,
> + .errp = &err,
> + .co = qemu_coroutine_self(),
> + };
> + aio_bh_schedule_oneshot(qemu_get_aio_context(), do_qmp_dispatch_bh,
> + &data);
> + qemu_coroutine_yield();
> + }
> qobject_unref(args);
> if (err) {
> /* or assert(!ret) after reviewing all handlers: */
> diff --git a/qapi/qmp-registry.c b/qapi/qmp-registry.c
> index d0f9a1d3e3..58c65b5052 100644
> --- a/qapi/qmp-registry.c
> +++ b/qapi/qmp-registry.c
> @@ -20,6 +20,9 @@ void qmp_register_command(QmpCommandList *cmds, const char
> *name,
> {
> QmpCommand *cmd = g_malloc0(sizeof(*cmd));
>
> + /* QCO_COROUTINE and QCO_ALLOW_OOB are incompatible for now */
> + assert(!((options & QCO_COROUTINE) && (options & QCO_ALLOW_OOB)));
> +
> cmd->name = name;
> cmd->fn = fn;
> cmd->enabled = true;
> diff --git a/util/aio-posix.c b/util/aio-posix.c
> index 280f27bb99..30f5354b1e 100644
> --- a/util/aio-posix.c
> +++ b/util/aio-posix.c
> @@ -15,6 +15,7 @@
>
> #include "qemu/osdep.h"
> #include "block/block.h"
> +#include "qemu/main-loop.h"
> #include "qemu/rcu.h"
> #include "qemu/rcu_queue.h"
> #include "qemu/sockets.h"
> @@ -558,8 +559,13 @@ bool aio_poll(AioContext *ctx, bool blocking)
> * There cannot be two concurrent aio_poll calls for the same AioContext
> (or
> * an aio_poll concurrent with a GSource prepare/check/dispatch
> callback).
> * We rely on this below to avoid slow locked accesses to ctx->notify_me.
> + *
> + * aio_poll() may only be called in the AioContext's thread.
> iohandler_ctx
> + * is special in that it runs in the main thread, but that thread's
> context
> + * is qemu_aio_context.
> */
> - assert(in_aio_context_home_thread(ctx));
> + assert(in_aio_context_home_thread(ctx == iohandler_get_aio_context() ?
> + qemu_get_aio_context() : ctx));
>
> qemu_lockcnt_inc(&ctx->list_lock);
--
Alex Bennée
