[Qemu-devel] [PATCH v10 0/7] monitor: let Monitor be thread safe

[Qemu-devel] [PATCH v10 0/7] monitor: let Monitor be thread safe

[Peter Xu]

v10:
- collect r-bs
- comment/renice the function monitor_get_clock(), add some commit
  message [Stefan, Markus]

v9:
- two more patches to implement Markus's idea to init monitor earlier
  (which are patch 5 & 6)
- touch up patch 7 to init the fdset lock in monitor_init_globals()

v8:
- some wording changes according to previous comments [Markus]
- return -ENOENT too in stubs/fdset.c:monitor_fdset_get_fd() [Stefan]
- refactor the fdset functions a bit, drop "ret" where proper [Markus]
- one more patch to fix monitor_lock comment [Markus]
- regular rebase and torturing

Stefan reported this problem that in the future we might start to have
more threads operating on the same Monitor object.  This seris try to
add fundamental support for it.

Please review.  Thanks,

Peter Xu (7):
  monitor: rename out_lock to mon_lock
  monitor: protect mon->fds with mon_lock
  monitor: more comments on lock-free elements
  monitor: fix comment for monitor_lock
  monitor: remove event_clock_type
  monitor: move init global earlier
  monitor: add lock to protect mon_fdsets

 monitor.c     | 168 +++++++++++++++++++++++++++++++++++---------------
 stubs/fdset.c |   2 +-
 util/osdep.c  |   3 +-
 vl.c          |   7 +--
 4 files changed, 121 insertions(+), 59 deletions(-)

-- 
2.17.1

[Qemu-devel] [PATCH v10 1/7] monitor: rename out_lock to mon_lock

[Peter Xu]

The out_lock is protecting a few Monitor fields.  In the future the
monitor code will start to run in multiple threads.  We are going to
turn it into a bigger lock to protect not only the out buffer but also
most of the rest.

Since at it, rearrange the Monitor struct a bit.

Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Peter Xu <peterx@redhat.com>
---
 monitor.c | 53 +++++++++++++++++++++++++++++------------------------
 1 file changed, 29 insertions(+), 24 deletions(-)

diff --git a/monitor.c b/monitor.c
index 6d0cec552e..5bc9b2dcd0 100644
--- a/monitor.c
+++ b/monitor.c
@@ -206,15 +206,6 @@ struct Monitor {
     int suspend_cnt;            /* Needs to be accessed atomically */
     bool skip_flush;
     bool use_io_thr;
-
-    /* We can't access guest memory when holding the lock */
-    QemuMutex out_lock;
-    QString *outbuf;
-    guint out_watch;
-
-    /* Read under either BQL or out_lock, written with BQL+out_lock.  */
-    int mux_out;
-
     ReadLineState *rs;
     MonitorQMP qmp;
     gchar *mon_cpu_path;
@@ -223,6 +214,20 @@ struct Monitor {
     mon_cmd_t *cmd_table;
     QLIST_HEAD(,mon_fd_t) fds;
     QTAILQ_ENTRY(Monitor) entry;
+
+    /*
+     * The per-monitor lock. We can't access guest memory when holding
+     * the lock.
+     */
+    QemuMutex mon_lock;
+
+    /*
+     * Fields that are protected by the per-monitor lock.
+     */
+    QString *outbuf;
+    guint out_watch;
+    /* Read under either BQL or mon_lock, written with BQL+mon_lock.  */
+    int mux_out;
 };
 
 /* Let's add monitor global variables to this struct. */
@@ -365,14 +370,14 @@ static gboolean monitor_unblocked(GIOChannel *chan, GIOCondition cond,
 {
     Monitor *mon = opaque;
 
-    qemu_mutex_lock(&mon->out_lock);
+    qemu_mutex_lock(&mon->mon_lock);
     mon->out_watch = 0;
     monitor_flush_locked(mon);
-    qemu_mutex_unlock(&mon->out_lock);
+    qemu_mutex_unlock(&mon->mon_lock);
     return FALSE;
 }
 
-/* Called with mon->out_lock held.  */
+/* Called with mon->mon_lock held.  */
 static void monitor_flush_locked(Monitor *mon)
 {
     int rc;
@@ -410,9 +415,9 @@ static void monitor_flush_locked(Monitor *mon)
 
 void monitor_flush(Monitor *mon)
 {
-    qemu_mutex_lock(&mon->out_lock);
+    qemu_mutex_lock(&mon->mon_lock);
     monitor_flush_locked(mon);
-    qemu_mutex_unlock(&mon->out_lock);
+    qemu_mutex_unlock(&mon->mon_lock);
 }
 
 /* flush at every end of line */
@@ -420,7 +425,7 @@ static void monitor_puts(Monitor *mon, const char *str)
 {
     char c;
 
-    qemu_mutex_lock(&mon->out_lock);
+    qemu_mutex_lock(&mon->mon_lock);
     for(;;) {
         c = *str++;
         if (c == '\0')
@@ -433,7 +438,7 @@ static void monitor_puts(Monitor *mon, const char *str)
             monitor_flush_locked(mon);
         }
     }
-    qemu_mutex_unlock(&mon->out_lock);
+    qemu_mutex_unlock(&mon->mon_lock);
 }
 
 void monitor_vprintf(Monitor *mon, const char *fmt, va_list ap)
@@ -724,7 +729,7 @@ static void monitor_data_init(Monitor *mon, bool skip_flush,
                               bool use_io_thr)
 {
     memset(mon, 0, sizeof(Monitor));
-    qemu_mutex_init(&mon->out_lock);
+    qemu_mutex_init(&mon->mon_lock);
     qemu_mutex_init(&mon->qmp.qmp_queue_lock);
     mon->outbuf = qstring_new();
     /* Use *mon_cmds by default. */
@@ -744,7 +749,7 @@ static void monitor_data_destroy(Monitor *mon)
     }
     readline_free(mon->rs);
     qobject_unref(mon->outbuf);
-    qemu_mutex_destroy(&mon->out_lock);
+    qemu_mutex_destroy(&mon->mon_lock);
     qemu_mutex_destroy(&mon->qmp.qmp_queue_lock);
     monitor_qmp_cleanup_req_queue_locked(mon);
     monitor_qmp_cleanup_resp_queue_locked(mon);
@@ -776,13 +781,13 @@ char *qmp_human_monitor_command(const char *command_line, bool has_cpu_index,
     handle_hmp_command(&hmp, command_line);
     cur_mon = old_mon;
 
-    qemu_mutex_lock(&hmp.out_lock);
+    qemu_mutex_lock(&hmp.mon_lock);
     if (qstring_get_length(hmp.outbuf) > 0) {
         output = g_strdup(qstring_get_str(hmp.outbuf));
     } else {
         output = g_strdup("");
     }
-    qemu_mutex_unlock(&hmp.out_lock);
+    qemu_mutex_unlock(&hmp.mon_lock);
 
 out:
     monitor_data_destroy(&hmp);
@@ -4381,9 +4386,9 @@ static void monitor_event(void *opaque, int event)
 
     switch (event) {
     case CHR_EVENT_MUX_IN:
-        qemu_mutex_lock(&mon->out_lock);
+        qemu_mutex_lock(&mon->mon_lock);
         mon->mux_out = 0;
-        qemu_mutex_unlock(&mon->out_lock);
+        qemu_mutex_unlock(&mon->mon_lock);
         if (mon->reset_seen) {
             readline_restart(mon->rs);
             monitor_resume(mon);
@@ -4403,9 +4408,9 @@ static void monitor_event(void *opaque, int event)
         } else {
             atomic_inc(&mon->suspend_cnt);
         }
-        qemu_mutex_lock(&mon->out_lock);
+        qemu_mutex_lock(&mon->mon_lock);
         mon->mux_out = 1;
-        qemu_mutex_unlock(&mon->out_lock);
+        qemu_mutex_unlock(&mon->mon_lock);
         break;
 
     case CHR_EVENT_OPENED:
-- 
2.17.1

[Qemu-devel] [PATCH v10 2/7] monitor: protect mon->fds with mon_lock

[Peter Xu]

mon->fds were protected by BQL.  Now protect it by mon_lock so that it
can even be used in monitor iothread.

Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Peter Xu <peterx@redhat.com>
---
 monitor.c | 22 ++++++++++++++++++----
 1 file changed, 18 insertions(+), 4 deletions(-)

diff --git a/monitor.c b/monitor.c
index 5bc9b2dcd0..0fba3ccc20 100644
--- a/monitor.c
+++ b/monitor.c
@@ -212,7 +212,6 @@ struct Monitor {
     BlockCompletionFunc *password_completion_cb;
     void *password_opaque;
     mon_cmd_t *cmd_table;
-    QLIST_HEAD(,mon_fd_t) fds;
     QTAILQ_ENTRY(Monitor) entry;
 
     /*
@@ -224,6 +223,7 @@ struct Monitor {
     /*
      * Fields that are protected by the per-monitor lock.
      */
+    QLIST_HEAD(, mon_fd_t) fds;
     QString *outbuf;
     guint out_watch;
     /* Read under either BQL or mon_lock, written with BQL+mon_lock.  */
@@ -2187,7 +2187,7 @@ static void hmp_acl_remove(Monitor *mon, const QDict *qdict)
 void qmp_getfd(const char *fdname, Error **errp)
 {
     mon_fd_t *monfd;
-    int fd;
+    int fd, tmp_fd;
 
     fd = qemu_chr_fe_get_msgfd(&cur_mon->chr);
     if (fd == -1) {
@@ -2202,13 +2202,17 @@ void qmp_getfd(const char *fdname, Error **errp)
         return;
     }
 
+    qemu_mutex_lock(&cur_mon->mon_lock);
     QLIST_FOREACH(monfd, &cur_mon->fds, next) {
         if (strcmp(monfd->name, fdname) != 0) {
             continue;
         }
 
-        close(monfd->fd);
+        tmp_fd = monfd->fd;
         monfd->fd = fd;
+        qemu_mutex_unlock(&cur_mon->mon_lock);
+        /* Make sure close() is out of critical section */
+        close(tmp_fd);
         return;
     }
 
@@ -2217,24 +2221,31 @@ void qmp_getfd(const char *fdname, Error **errp)
     monfd->fd = fd;
 
     QLIST_INSERT_HEAD(&cur_mon->fds, monfd, next);
+    qemu_mutex_unlock(&cur_mon->mon_lock);
 }
 
 void qmp_closefd(const char *fdname, Error **errp)
 {
     mon_fd_t *monfd;
+    int tmp_fd;
 
+    qemu_mutex_lock(&cur_mon->mon_lock);
     QLIST_FOREACH(monfd, &cur_mon->fds, next) {
         if (strcmp(monfd->name, fdname) != 0) {
             continue;
         }
 
         QLIST_REMOVE(monfd, next);
-        close(monfd->fd);
+        tmp_fd = monfd->fd;
         g_free(monfd->name);
         g_free(monfd);
+        qemu_mutex_unlock(&cur_mon->mon_lock);
+        /* Make sure close() is out of critical section */
+        close(tmp_fd);
         return;
     }
 
+    qemu_mutex_unlock(&cur_mon->mon_lock);
     error_setg(errp, QERR_FD_NOT_FOUND, fdname);
 }
 
@@ -2242,6 +2253,7 @@ int monitor_get_fd(Monitor *mon, const char *fdname, Error **errp)
 {
     mon_fd_t *monfd;
 
+    qemu_mutex_lock(&mon->mon_lock);
     QLIST_FOREACH(monfd, &mon->fds, next) {
         int fd;
 
@@ -2255,10 +2267,12 @@ int monitor_get_fd(Monitor *mon, const char *fdname, Error **errp)
         QLIST_REMOVE(monfd, next);
         g_free(monfd->name);
         g_free(monfd);
+        qemu_mutex_unlock(&mon->mon_lock);
 
         return fd;
     }
 
+    qemu_mutex_unlock(&mon->mon_lock);
     error_setg(errp, "File descriptor named '%s' has not been found", fdname);
     return -1;
 }
-- 
2.17.1

[Qemu-devel] [PATCH v10 3/7] monitor: more comments on lock-free elements

[Peter Xu]

Add some explicit comments for both Readline and cpu_set/cpu_get helpers
that they do not need the mon_lock protection.

Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Peter Xu <peterx@redhat.com>
---
 monitor.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/monitor.c b/monitor.c
index 0fba3ccc20..5c60bf08cc 100644
--- a/monitor.c
+++ b/monitor.c
@@ -206,7 +206,15 @@ struct Monitor {
     int suspend_cnt;            /* Needs to be accessed atomically */
     bool skip_flush;
     bool use_io_thr;
+
+    /*
+     * State used only in the thread "owning" the monitor.
+     * If @use_io_thr, this is mon_global.mon_iothread.
+     * Else, it's the main thread.
+     * These members can be safely accessed without locks.
+     */
     ReadLineState *rs;
+
     MonitorQMP qmp;
     gchar *mon_cpu_path;
     BlockCompletionFunc *password_completion_cb;
@@ -1311,7 +1319,7 @@ void qmp_qmp_capabilities(bool has_enable, QMPCapabilityList *enable,
     cur_mon->qmp.commands = &qmp_commands;
 }
 
-/* set the current CPU defined by the user */
+/* Set the current CPU defined by the user. Callers must hold BQL. */
 int monitor_set_cpu(int cpu_index)
 {
     CPUState *cpu;
@@ -1325,6 +1333,7 @@ int monitor_set_cpu(int cpu_index)
     return 0;
 }
 
+/* Callers must hold BQL. */
 static CPUState *mon_get_cpu_sync(bool synchronize)
 {
     CPUState *cpu;
-- 
2.17.1

[Qemu-devel] [PATCH v10 4/7] monitor: fix comment for monitor_lock

[Peter Xu]

Fix typo in d622cb5879c.  Meanwhile move these variables close to each
other.  monitor_qapi_event_state can be declared static, add that.

Reported-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Peter Xu <peterx@redhat.com>
---
 monitor.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/monitor.c b/monitor.c
index 5c60bf08cc..fa9c35631f 100644
--- a/monitor.c
+++ b/monitor.c
@@ -266,10 +266,11 @@ typedef struct QMPRequest QMPRequest;
 /* QMP checker flags */
 #define QMP_ACCEPT_UNKNOWNS 1
 
-/* Protects mon_list, monitor_event_state.  */
+/* Protects mon_list, monitor_qapi_event_state.  */
 static QemuMutex monitor_lock;
-
+static GHashTable *monitor_qapi_event_state;
 static QTAILQ_HEAD(mon_list, Monitor) mon_list;
+
 static QLIST_HEAD(mon_fdsets, MonFdset) mon_fdsets;
 static int mon_refcount;
 
@@ -571,8 +572,6 @@ static MonitorQAPIEventConf monitor_qapi_event_conf[QAPI_EVENT__MAX] = {
     [QAPI_EVENT_VSERPORT_CHANGE]   = { 1000 * SCALE_MS },
 };
 
-GHashTable *monitor_qapi_event_state;
-
 /*
  * Emits the event to every monitor instance, @event is only used for trace
  * Called with monitor_lock held.
-- 
2.17.1

[Qemu-devel] [PATCH v10 5/7] monitor: remove event_clock_type

[Peter Xu]

Instead, use a dynamic function to detect which clock we'll use.  The
problem is that the old code will let monitor initialization depend on
configure_accelerator() (that's where qtest_enabled() start to take
effect).  After this change, we don't have such a dependency any more.
We just need to make sure configure_accelerator() is called when we
start to use it.  Now it's only used in monitor_qapi_event_queue() and
monitor_qapi_event_handler(), so we're good.

Suggested-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Peter Xu <peterx@redhat.com>
---
 monitor.c | 25 ++++++++++++++++---------
 1 file changed, 16 insertions(+), 9 deletions(-)

diff --git a/monitor.c b/monitor.c
index fa9c35631f..2bda0dfa12 100644
--- a/monitor.c
+++ b/monitor.c
@@ -281,8 +281,6 @@ QmpCommandList qmp_commands, qmp_cap_negotiation_commands;
 
 Monitor *cur_mon;
 
-static QEMUClockType event_clock_type = QEMU_CLOCK_REALTIME;
-
 static void monitor_command_cb(void *opaque, const char *cmdline,
                                void *readline_opaque);
 
@@ -309,6 +307,19 @@ static inline bool monitor_is_hmp_non_interactive(const Monitor *mon)
     return !monitor_is_qmp(mon) && !monitor_uses_readline(mon);
 }
 
+/*
+ * This should never be called before configure_accelerator() since
+ * only until then could we know whether qtest was enabled or not.
+ */
+static inline QEMUClockType monitor_get_clock(void)
+{
+    /*
+     * This allows us to perform tests on the monitor queues to verify
+     * that the rate limits are enforced.
+     */
+    return qtest_enabled() ? QEMU_CLOCK_VIRTUAL : QEMU_CLOCK_REALTIME;
+}
+
 /**
  * Is the current monitor, if any, a QMP monitor?
  */
@@ -632,7 +643,7 @@ monitor_qapi_event_queue(QAPIEvent event, QDict *qdict, Error **errp)
              * monitor_qapi_event_handler() in evconf->rate ns.  Any
              * events arriving before then will be delayed until then.
              */
-            int64_t now = qemu_clock_get_ns(event_clock_type);
+            int64_t now = qemu_clock_get_ns(monitor_get_clock());
 
             monitor_qapi_event_emit(event, qdict);
 
@@ -640,7 +651,7 @@ monitor_qapi_event_queue(QAPIEvent event, QDict *qdict, Error **errp)
             evstate->event = event;
             evstate->data = qobject_ref(data);
             evstate->qdict = NULL;
-            evstate->timer = timer_new_ns(event_clock_type,
+            evstate->timer = timer_new_ns(monitor_get_clock(),
                                           monitor_qapi_event_handler,
                                           evstate);
             g_hash_table_add(monitor_qapi_event_state, evstate);
@@ -665,7 +676,7 @@ static void monitor_qapi_event_handler(void *opaque)
     qemu_mutex_lock(&monitor_lock);
 
     if (evstate->qdict) {
-        int64_t now = qemu_clock_get_ns(event_clock_type);
+        int64_t now = qemu_clock_get_ns(monitor_get_clock());
 
         monitor_qapi_event_emit(evstate->event, evstate->qdict);
         qobject_unref(evstate->qdict);
@@ -721,10 +732,6 @@ static gboolean qapi_event_throttle_equal(const void *a, const void *b)
 
 static void monitor_qapi_event_init(void)
 {
-    if (qtest_enabled()) {
-        event_clock_type = QEMU_CLOCK_VIRTUAL;
-    }
-
     monitor_qapi_event_state = g_hash_table_new(qapi_event_throttle_hash,
                                                 qapi_event_throttle_equal);
     qmp_event_set_func_emit(monitor_qapi_event_queue);
-- 
2.17.1

Re: [Qemu-devel] [PATCH v10 5/7] monitor: remove event_clock_type

[Markus Armbruster]

Peter Xu <peterx@redhat.com> writes:

> Instead, use a dynamic function to detect which clock we'll use.  The
> problem is that the old code will let monitor initialization depend on
> configure_accelerator() (that's where qtest_enabled() start to take
> effect).  After this change, we don't have such a dependency any more.
> We just need to make sure configure_accelerator() is called when we
> start to use it.  Now it's only used in monitor_qapi_event_queue() and
> monitor_qapi_event_handler(), so we're good.
>
> Suggested-by: Markus Armbruster <armbru@redhat.com>
> Signed-off-by: Peter Xu <peterx@redhat.com>
> ---
>  monitor.c | 25 ++++++++++++++++---------
>  1 file changed, 16 insertions(+), 9 deletions(-)
>
> diff --git a/monitor.c b/monitor.c
> index fa9c35631f..2bda0dfa12 100644
> --- a/monitor.c
> +++ b/monitor.c
> @@ -281,8 +281,6 @@ QmpCommandList qmp_commands, qmp_cap_negotiation_commands;
>  
>  Monitor *cur_mon;
>  
> -static QEMUClockType event_clock_type = QEMU_CLOCK_REALTIME;
> -
>  static void monitor_command_cb(void *opaque, const char *cmdline,
>                                 void *readline_opaque);
>  
> @@ -309,6 +307,19 @@ static inline bool monitor_is_hmp_non_interactive(const Monitor *mon)
>      return !monitor_is_qmp(mon) && !monitor_uses_readline(mon);
>  }
>  
> +/*
> + * This should never be called before configure_accelerator() since
> + * only until then could we know whether qtest was enabled or not.

Uh, we know it after then, not until then.  What about

   /*
    * Return the clock to use for recording an event's time.
    * Beware: result is invalid before configure_accelerator().

> + */
> +static inline QEMUClockType monitor_get_clock(void)

Suggest to rename to monitor_get_event_clock(), or just
get_event_clock().

Happy to apply touch-ups on commit.

> +{
> +    /*
> +     * This allows us to perform tests on the monitor queues to verify
> +     * that the rate limits are enforced.
> +     */
> +    return qtest_enabled() ? QEMU_CLOCK_VIRTUAL : QEMU_CLOCK_REALTIME;
> +}
> +
>  /**
>   * Is the current monitor, if any, a QMP monitor?
>   */
> @@ -632,7 +643,7 @@ monitor_qapi_event_queue(QAPIEvent event, QDict *qdict, Error **errp)
>               * monitor_qapi_event_handler() in evconf->rate ns.  Any
>               * events arriving before then will be delayed until then.
>               */
> -            int64_t now = qemu_clock_get_ns(event_clock_type);
> +            int64_t now = qemu_clock_get_ns(monitor_get_clock());
>  
>              monitor_qapi_event_emit(event, qdict);
>  
> @@ -640,7 +651,7 @@ monitor_qapi_event_queue(QAPIEvent event, QDict *qdict, Error **errp)
>              evstate->event = event;
>              evstate->data = qobject_ref(data);
>              evstate->qdict = NULL;
> -            evstate->timer = timer_new_ns(event_clock_type,
> +            evstate->timer = timer_new_ns(monitor_get_clock(),
>                                            monitor_qapi_event_handler,
>                                            evstate);
>              g_hash_table_add(monitor_qapi_event_state, evstate);
> @@ -665,7 +676,7 @@ static void monitor_qapi_event_handler(void *opaque)
>      qemu_mutex_lock(&monitor_lock);
>  
>      if (evstate->qdict) {
> -        int64_t now = qemu_clock_get_ns(event_clock_type);
> +        int64_t now = qemu_clock_get_ns(monitor_get_clock());
>  
>          monitor_qapi_event_emit(evstate->event, evstate->qdict);
>          qobject_unref(evstate->qdict);
> @@ -721,10 +732,6 @@ static gboolean qapi_event_throttle_equal(const void *a, const void *b)
>  
>  static void monitor_qapi_event_init(void)
>  {
> -    if (qtest_enabled()) {
> -        event_clock_type = QEMU_CLOCK_VIRTUAL;
> -    }
> -
>      monitor_qapi_event_state = g_hash_table_new(qapi_event_throttle_hash,
>                                                  qapi_event_throttle_equal);
>      qmp_event_set_func_emit(monitor_qapi_event_queue);

With at least a suitable fix for the comment:
Reviewed-by: Markus Armbruster <armbru@redhat.com>

Re: [Qemu-devel] [PATCH v10 5/7] monitor: remove event_clock_type

[Peter Xu]

On Fri, Jun 08, 2018 at 07:38:11AM +0200, Markus Armbruster wrote:

[...]

> > +/*
> > + * This should never be called before configure_accelerator() since
> > + * only until then could we know whether qtest was enabled or not.
> 
> Uh, we know it after then, not until then.  What about
> 
>    /*
>     * Return the clock to use for recording an event's time.
>     * Beware: result is invalid before configure_accelerator().

Oh, another Chinglish from me. :(

> 
> > + */
> > +static inline QEMUClockType monitor_get_clock(void)
> 
> Suggest to rename to monitor_get_event_clock(), or just
> get_event_clock().
> 
> Happy to apply touch-ups on commit.

That'll be appreciated.  Both changes work for me.

[...]

> With at least a suitable fix for the comment:
> Reviewed-by: Markus Armbruster <armbru@redhat.com>

Thanks!

-- 
Peter Xu

Re: [Qemu-devel] [PATCH v10 5/7] monitor: remove event_clock_type

[Markus Armbruster]

Peter Xu <peterx@redhat.com> writes:

> On Fri, Jun 08, 2018 at 07:38:11AM +0200, Markus Armbruster wrote:
>
> [...]
>
>> > +/*
>> > + * This should never be called before configure_accelerator() since
>> > + * only until then could we know whether qtest was enabled or not.
>> 
>> Uh, we know it after then, not until then.  What about
>> 
>>    /*
>>     * Return the clock to use for recording an event's time.
>>     * Beware: result is invalid before configure_accelerator().
>
> Oh, another Chinglish from me. :(

Useful code, occasional Chinglish, the humility to go with it, and a
sense of humor --- you're doing fine.

[...]

Re: [Qemu-devel] [PATCH v10 5/7] monitor: remove event_clock_type

[Peter Xu]

On Fri, Jun 08, 2018 at 09:09:57AM +0200, Markus Armbruster wrote:
> Peter Xu <peterx@redhat.com> writes:
> 
> > On Fri, Jun 08, 2018 at 07:38:11AM +0200, Markus Armbruster wrote:
> >
> > [...]
> >
> >> > +/*
> >> > + * This should never be called before configure_accelerator() since
> >> > + * only until then could we know whether qtest was enabled or not.
> >> 
> >> Uh, we know it after then, not until then.  What about
> >> 
> >>    /*
> >>     * Return the clock to use for recording an event's time.
> >>     * Beware: result is invalid before configure_accelerator().
> >
> > Oh, another Chinglish from me. :(
> 
> Useful code, occasional Chinglish, the humility to go with it, and a
> sense of humor --- you're doing fine.

Very high evaluation. Thank you. :)

-- 
Peter Xu

Re: [Qemu-devel] [PATCH v10 5/7] monitor: remove event_clock_type

[Stefan Hajnoczi]

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On Fri, Jun 08, 2018 at 11:55:09AM +0800, Peter Xu wrote:
> Instead, use a dynamic function to detect which clock we'll use.  The
> problem is that the old code will let monitor initialization depend on
> configure_accelerator() (that's where qtest_enabled() start to take
> effect).  After this change, we don't have such a dependency any more.
> We just need to make sure configure_accelerator() is called when we
> start to use it.  Now it's only used in monitor_qapi_event_queue() and
> monitor_qapi_event_handler(), so we're good.
> 
> Suggested-by: Markus Armbruster <armbru@redhat.com>
> Signed-off-by: Peter Xu <peterx@redhat.com>
> ---
>  monitor.c | 25 ++++++++++++++++---------
>  1 file changed, 16 insertions(+), 9 deletions(-)

With Markus' suggestion:

Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>

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[Qemu-devel] [PATCH v10 6/7] monitor: move init global earlier

[Peter Xu]

Before this patch, monitor fd helpers might be called even earlier than
monitor_init_globals().  This can be problematic.

After previous work, now monitor_init_globals() does not depend on
accelerator initialization any more.  Call it earlier (before CLI
parsing; that's where the monitor APIs might be called) to make sure it
is called before any of the monitor APIs.

Suggested-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Peter Xu <peterx@redhat.com>
---
 vl.c | 7 +------
 1 file changed, 1 insertion(+), 6 deletions(-)

diff --git a/vl.c b/vl.c
index 06031715ac..5ddea3d235 100644
--- a/vl.c
+++ b/vl.c
@@ -2978,6 +2978,7 @@ int main(int argc, char **argv, char **envp)
 
     runstate_init();
     postcopy_infrastructure_init();
+    monitor_init_globals();
 
     if (qcrypto_init(&err) < 0) {
         error_reportf_err(err, "cannot initialize crypto: ");
@@ -4412,12 +4413,6 @@ int main(int argc, char **argv, char **envp)
     default_drive(default_floppy, snapshot, IF_FLOPPY, 0, FD_OPTS);
     default_drive(default_sdcard, snapshot, IF_SD, 0, SD_OPTS);
 
-    /*
-     * Note: qtest_enabled() (which is used in monitor_qapi_event_init())
-     * depends on configure_accelerator() above.
-     */
-    monitor_init_globals();
-
     if (qemu_opts_foreach(qemu_find_opts("mon"),
                           mon_init_func, NULL, NULL)) {
         exit(1);
-- 
2.17.1

[Qemu-devel] [PATCH v10 7/7] monitor: add lock to protect mon_fdsets

[Peter Xu]

Introduce a new global big lock for mon_fdsets.  Take it where needed.

The monitor_fdset_get_fd() handling is a bit tricky: now we need to call
qemu_mutex_unlock() which might pollute errno, so we need to make sure
the correct errno be passed up to the callers.  To make things simpler,
we let monitor_fdset_get_fd() return the -errno directly when error
happens, then in qemu_open() we move it back into errno.

Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Peter Xu <peterx@redhat.com>
---
 monitor.c     | 52 +++++++++++++++++++++++++++++++++++++++++----------
 stubs/fdset.c |  2 +-
 util/osdep.c  |  3 ++-
 3 files changed, 45 insertions(+), 12 deletions(-)

diff --git a/monitor.c b/monitor.c
index 2bda0dfa12..ede4aed8b6 100644
--- a/monitor.c
+++ b/monitor.c
@@ -271,7 +271,10 @@ static QemuMutex monitor_lock;
 static GHashTable *monitor_qapi_event_state;
 static QTAILQ_HEAD(mon_list, Monitor) mon_list;
 
+/* Protects mon_fdsets */
+static QemuMutex mon_fdsets_lock;
 static QLIST_HEAD(mon_fdsets, MonFdset) mon_fdsets;
+
 static int mon_refcount;
 
 static mon_cmd_t mon_cmds[];
@@ -2319,9 +2322,11 @@ static void monitor_fdsets_cleanup(void)
     MonFdset *mon_fdset;
     MonFdset *mon_fdset_next;
 
+    qemu_mutex_lock(&mon_fdsets_lock);
     QLIST_FOREACH_SAFE(mon_fdset, &mon_fdsets, next, mon_fdset_next) {
         monitor_fdset_cleanup(mon_fdset);
     }
+    qemu_mutex_unlock(&mon_fdsets_lock);
 }
 
 AddfdInfo *qmp_add_fd(bool has_fdset_id, int64_t fdset_id, bool has_opaque,
@@ -2356,6 +2361,7 @@ void qmp_remove_fd(int64_t fdset_id, bool has_fd, int64_t fd, Error **errp)
     MonFdsetFd *mon_fdset_fd;
     char fd_str[60];
 
+    qemu_mutex_lock(&mon_fdsets_lock);
     QLIST_FOREACH(mon_fdset, &mon_fdsets, next) {
         if (mon_fdset->id != fdset_id) {
             continue;
@@ -2375,10 +2381,12 @@ void qmp_remove_fd(int64_t fdset_id, bool has_fd, int64_t fd, Error **errp)
             goto error;
         }
         monitor_fdset_cleanup(mon_fdset);
+        qemu_mutex_unlock(&mon_fdsets_lock);
         return;
     }
 
 error:
+    qemu_mutex_unlock(&mon_fdsets_lock);
     if (has_fd) {
         snprintf(fd_str, sizeof(fd_str), "fdset-id:%" PRId64 ", fd:%" PRId64,
                  fdset_id, fd);
@@ -2394,6 +2402,7 @@ FdsetInfoList *qmp_query_fdsets(Error **errp)
     MonFdsetFd *mon_fdset_fd;
     FdsetInfoList *fdset_list = NULL;
 
+    qemu_mutex_lock(&mon_fdsets_lock);
     QLIST_FOREACH(mon_fdset, &mon_fdsets, next) {
         FdsetInfoList *fdset_info = g_malloc0(sizeof(*fdset_info));
         FdsetFdInfoList *fdsetfd_list = NULL;
@@ -2423,6 +2432,7 @@ FdsetInfoList *qmp_query_fdsets(Error **errp)
         fdset_info->next = fdset_list;
         fdset_list = fdset_info;
     }
+    qemu_mutex_unlock(&mon_fdsets_lock);
 
     return fdset_list;
 }
@@ -2435,6 +2445,7 @@ AddfdInfo *monitor_fdset_add_fd(int fd, bool has_fdset_id, int64_t fdset_id,
     MonFdsetFd *mon_fdset_fd;
     AddfdInfo *fdinfo;
 
+    qemu_mutex_lock(&mon_fdsets_lock);
     if (has_fdset_id) {
         QLIST_FOREACH(mon_fdset, &mon_fdsets, next) {
             /* Break if match found or match impossible due to ordering by ID */
@@ -2455,6 +2466,7 @@ AddfdInfo *monitor_fdset_add_fd(int fd, bool has_fdset_id, int64_t fdset_id,
             if (fdset_id < 0) {
                 error_setg(errp, QERR_INVALID_PARAMETER_VALUE, "fdset-id",
                            "a non-negative value");
+                qemu_mutex_unlock(&mon_fdsets_lock);
                 return NULL;
             }
             /* Use specified fdset ID */
@@ -2505,16 +2517,21 @@ AddfdInfo *monitor_fdset_add_fd(int fd, bool has_fdset_id, int64_t fdset_id,
     fdinfo->fdset_id = mon_fdset->id;
     fdinfo->fd = mon_fdset_fd->fd;
 
+    qemu_mutex_unlock(&mon_fdsets_lock);
     return fdinfo;
 }
 
 int monitor_fdset_get_fd(int64_t fdset_id, int flags)
 {
-#ifndef _WIN32
+#ifdef _WIN32
+    return -ENOENT;
+#else
     MonFdset *mon_fdset;
     MonFdsetFd *mon_fdset_fd;
     int mon_fd_flags;
+    int ret;
 
+    qemu_mutex_lock(&mon_fdsets_lock);
     QLIST_FOREACH(mon_fdset, &mon_fdsets, next) {
         if (mon_fdset->id != fdset_id) {
             continue;
@@ -2522,20 +2539,24 @@ int monitor_fdset_get_fd(int64_t fdset_id, int flags)
         QLIST_FOREACH(mon_fdset_fd, &mon_fdset->fds, next) {
             mon_fd_flags = fcntl(mon_fdset_fd->fd, F_GETFL);
             if (mon_fd_flags == -1) {
-                return -1;
+                ret = -errno;
+                goto out;
             }
 
             if ((flags & O_ACCMODE) == (mon_fd_flags & O_ACCMODE)) {
-                return mon_fdset_fd->fd;
+                ret = mon_fdset_fd->fd;
+                goto out;
             }
         }
-        errno = EACCES;
-        return -1;
+        ret = -EACCES;
+        goto out;
     }
-#endif
+    ret = -ENOENT;
 
-    errno = ENOENT;
-    return -1;
+out:
+    qemu_mutex_unlock(&mon_fdsets_lock);
+    return ret;
+#endif
 }
 
 int monitor_fdset_dup_fd_add(int64_t fdset_id, int dup_fd)
@@ -2543,20 +2564,25 @@ int monitor_fdset_dup_fd_add(int64_t fdset_id, int dup_fd)
     MonFdset *mon_fdset;
     MonFdsetFd *mon_fdset_fd_dup;
 
+    qemu_mutex_lock(&mon_fdsets_lock);
     QLIST_FOREACH(mon_fdset, &mon_fdsets, next) {
         if (mon_fdset->id != fdset_id) {
             continue;
         }
         QLIST_FOREACH(mon_fdset_fd_dup, &mon_fdset->dup_fds, next) {
             if (mon_fdset_fd_dup->fd == dup_fd) {
-                return -1;
+                goto err;
             }
         }
         mon_fdset_fd_dup = g_malloc0(sizeof(*mon_fdset_fd_dup));
         mon_fdset_fd_dup->fd = dup_fd;
         QLIST_INSERT_HEAD(&mon_fdset->dup_fds, mon_fdset_fd_dup, next);
+        qemu_mutex_unlock(&mon_fdsets_lock);
         return 0;
     }
+
+err:
+    qemu_mutex_unlock(&mon_fdsets_lock);
     return -1;
 }
 
@@ -2565,6 +2591,7 @@ static int monitor_fdset_dup_fd_find_remove(int dup_fd, bool remove)
     MonFdset *mon_fdset;
     MonFdsetFd *mon_fdset_fd_dup;
 
+    qemu_mutex_lock(&mon_fdsets_lock);
     QLIST_FOREACH(mon_fdset, &mon_fdsets, next) {
         QLIST_FOREACH(mon_fdset_fd_dup, &mon_fdset->dup_fds, next) {
             if (mon_fdset_fd_dup->fd == dup_fd) {
@@ -2573,13 +2600,17 @@ static int monitor_fdset_dup_fd_find_remove(int dup_fd, bool remove)
                     if (QLIST_EMPTY(&mon_fdset->dup_fds)) {
                         monitor_fdset_cleanup(mon_fdset);
                     }
-                    return -1;
+                    goto err;
                 } else {
+                    qemu_mutex_unlock(&mon_fdsets_lock);
                     return mon_fdset->id;
                 }
             }
         }
     }
+
+err:
+    qemu_mutex_unlock(&mon_fdsets_lock);
     return -1;
 }
 
@@ -4519,6 +4550,7 @@ void monitor_init_globals(void)
     monitor_qapi_event_init();
     sortcmdlist();
     qemu_mutex_init(&monitor_lock);
+    qemu_mutex_init(&mon_fdsets_lock);
     monitor_iothread_init();
 }
 
diff --git a/stubs/fdset.c b/stubs/fdset.c
index 6020cf28c8..4f3edf2ea4 100644
--- a/stubs/fdset.c
+++ b/stubs/fdset.c
@@ -14,7 +14,7 @@ int monitor_fdset_dup_fd_find(int dup_fd)
 
 int monitor_fdset_get_fd(int64_t fdset_id, int flags)
 {
-    return -1;
+    return -ENOENT;
 }
 
 void monitor_fdset_dup_fd_remove(int dupfd)
diff --git a/util/osdep.c b/util/osdep.c
index a73de0e1ba..ea51d500b6 100644
--- a/util/osdep.c
+++ b/util/osdep.c
@@ -302,7 +302,8 @@ int qemu_open(const char *name, int flags, ...)
         }
 
         fd = monitor_fdset_get_fd(fdset_id, flags);
-        if (fd == -1) {
+        if (fd < 0) {
+            errno = -fd;
             return -1;
         }
 
-- 
2.17.1