[Qemu-devel] [PULL v2 0/3] Monitor patches for 2018-10-30

[Qemu-devel] [PULL v2 0/3] Monitor patches for 2018-10-30

[Markus Armbruster]

The following changes since commit 0ca70f19c010ccf0b10cf7cc1d2b9a87193fe787:

  tests: Fix Python 3 detection on older GNU make versions (2018-11-06 14:58:13 +0000)

are available in the Git repository at:

  git://repo.or.cz/qemu/armbru.git tags/pull-monitor-2018-10-30-v2

for you to fetch changes up to 0c57893d62596d1d91779452be3b38b4b72ecd04:

  vl: Avoid crash when -mon is underspecified (2018-11-06 17:03:29 +0100)

----------------------------------------------------------------
Monitor patches for 2018-10-30

* Fix crash on shutdown with --daemonize
* Avoid crash when -mon lacks chardev=...

----------------------------------------------------------------
Eric Blake (1):
      vl: Avoid crash when -mon is underspecified

Wolfgang Bumiller (2):
      monitor: guard iothread access by mon->use_io_thread
      monitor: delay monitor iothread creation

 monitor.c | 37 ++++++++++++++++++++++---------------
 vl.c      |  4 ++++
 2 files changed, 26 insertions(+), 15 deletions(-)

Eric Blake (1):
  vl: Avoid crash when -mon is underspecified

Wolfgang Bumiller (2):
  monitor: guard iothread access by mon->use_io_thread
  monitor: delay monitor iothread creation

 monitor.c | 37 ++++++++++++++++++++++---------------
 vl.c      |  4 ++++
 2 files changed, 26 insertions(+), 15 deletions(-)

-- 
2.17.2

[Qemu-devel] [PULL v2 1/3] monitor: guard iothread access by mon->use_io_thread

[Markus Armbruster]

From: Wolfgang Bumiller <w.bumiller@proxmox.com>

monitor_resume() and monitor_suspend() both want to
"kick" the I/O thread if it is there, but in
monitor_suspend() lacked the use_io_thread flag condition.
This is required when we later only spawn the thread on
first use.

Signed-off-by: Wolfgang Bumiller <w.bumiller@proxmox.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
Message-Id: <20180925081507.11873-2-w.bumiller@proxmox.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>
---
 monitor.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/monitor.c b/monitor.c
index 823b5a1099..66f149c1dc 100644
--- a/monitor.c
+++ b/monitor.c
@@ -4292,7 +4292,7 @@ int monitor_suspend(Monitor *mon)
 
     atomic_inc(&mon->suspend_cnt);
 
-    if (monitor_is_qmp(mon)) {
+    if (monitor_is_qmp(mon) && mon->use_io_thread) {
         /*
          * Kick I/O thread to make sure this takes effect.  It'll be
          * evaluated again in prepare() of the watch object.
-- 
2.17.2

[Qemu-devel] [PULL v2 2/3] monitor: delay monitor iothread creation

[Markus Armbruster]

From: Wolfgang Bumiller <w.bumiller@proxmox.com>

Commit d32749deb615 moved the call to monitor_init_globals()
to before os_daemonize(), making it an unsuitable place to
spawn the monitor iothread as it won't be inherited over the
fork() in os_daemonize().

We now spawn the thread the first time we instantiate a
monitor which actually has use_io_thread == true.
Instantiation of monitors happens only after os_daemonize().
We still need to create the qmp_dispatcher_bh when not using
iothreads, so this now still happens in
monitor_init_globals().

Signed-off-by: Wolfgang Bumiller <w.bumiller@proxmox.com>
Fixes: d32749deb615 ("monitor: move init global earlier")
Message-Id: <20180925081507.11873-3-w.bumiller@proxmox.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
Tested-by: Peter Xu <peterx@redhat.com>
[This fixes a crash on shutdown with --daemonize]
Signed-off-by: Markus Armbruster <armbru@redhat.com>
---
 monitor.c | 35 +++++++++++++++++++++--------------
 1 file changed, 21 insertions(+), 14 deletions(-)

diff --git a/monitor.c b/monitor.c
index 66f149c1dc..d39390c2f2 100644
--- a/monitor.c
+++ b/monitor.c
@@ -708,9 +708,14 @@ static void monitor_qapi_event_init(void)
 
 static void handle_hmp_command(Monitor *mon, const char *cmdline);
 
+static void monitor_iothread_init(void);
+
 static void monitor_data_init(Monitor *mon, bool skip_flush,
                               bool use_io_thread)
 {
+    if (use_io_thread && !mon_iothread) {
+        monitor_iothread_init();
+    }
     memset(mon, 0, sizeof(Monitor));
     qemu_mutex_init(&mon->mon_lock);
     qemu_mutex_init(&mon->qmp.qmp_queue_lock);
@@ -4461,15 +4466,6 @@ static AioContext *monitor_get_aio_context(void)
 static void monitor_iothread_init(void)
 {
     mon_iothread = iothread_create("mon_iothread", &error_abort);
-
-    /*
-     * The dispatcher BH must run in the main loop thread, since we
-     * 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);
 }
 
 void monitor_init_globals(void)
@@ -4479,7 +4475,15 @@ void monitor_init_globals(void)
     sortcmdlist();
     qemu_mutex_init(&monitor_lock);
     qemu_mutex_init(&mon_fdsets_lock);
-    monitor_iothread_init();
+
+    /*
+     * The dispatcher BH must run in the main loop thread, since we
+     * 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);
 }
 
 /* These functions just adapt the readline interface in a typesafe way.  We
@@ -4624,7 +4628,9 @@ void monitor_cleanup(void)
      * we need to unregister from chardev below in
      * monitor_data_destroy(), and chardev is not thread-safe yet
      */
-    iothread_stop(mon_iothread);
+    if (mon_iothread) {
+        iothread_stop(mon_iothread);
+    }
 
     /* Flush output buffers and destroy monitors */
     qemu_mutex_lock(&monitor_lock);
@@ -4639,9 +4645,10 @@ void monitor_cleanup(void)
     /* QEMUBHs needs to be deleted before destroying the I/O thread */
     qemu_bh_delete(qmp_dispatcher_bh);
     qmp_dispatcher_bh = NULL;
-
-    iothread_destroy(mon_iothread);
-    mon_iothread = NULL;
+    if (mon_iothread) {
+        iothread_destroy(mon_iothread);
+        mon_iothread = NULL;
+    }
 }
 
 QemuOptsList qemu_mon_opts = {
-- 
2.17.2

[Qemu-devel] [PULL v2 3/3] vl: Avoid crash when -mon is underspecified

[Markus Armbruster]

From: Eric Blake <eblake@redhat.com>

A quick coredump on an incomplete command line:
./x86_64-softmmu/qemu-system-x86_64 -mon mode=control,pretty=on

 #0  0x00007ffff723d9e4 in g_str_hash () at /lib64/libglib-2.0.so.0
 #1  0x00007ffff723ce38 in g_hash_table_lookup () at /lib64/libglib-2.0.so.0
 #2  0x0000555555cc0073 in object_class_property_find (klass=0x5555566a94b0, name=0x0, errp=0x0) at qom/object.c:1135
 #3  0x0000555555cc004b in object_class_property_find (klass=0x5555566a9440, name=0x0, errp=0x0) at qom/object.c:1129
 #4  0x0000555555cbfe6e in object_property_find (obj=0x5555568348c0, name=0x0, errp=0x0) at qom/object.c:1080
 #5  0x0000555555cc183d in object_resolve_path_component (parent=0x5555568348c0, part=0x0) at qom/object.c:1762
 #6  0x0000555555d82071 in qemu_chr_find (name=0x0) at chardev/char.c:802
 #7  0x00005555559d77cb in mon_init_func (opaque=0x0, opts=0x5555566b65a0, errp=0x0) at vl.c:2291

Fix it to instead fail gracefully.

Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20181023213600.364086-1-eblake@redhat.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>
---
 vl.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/vl.c b/vl.c
index 03ed215d7b..55bab005b6 100644
--- a/vl.c
+++ b/vl.c
@@ -2323,6 +2323,10 @@ static int mon_init_func(void *opaque, QemuOpts *opts, Error **errp)
     }
 
     chardev = qemu_opt_get(opts, "chardev");
+    if (!chardev) {
+        error_report("chardev is required");
+        exit(1);
+    }
     chr = qemu_chr_find(chardev);
     if (chr == NULL) {
         error_setg(errp, "chardev \"%s\" not found", chardev);
-- 
2.17.2

Re: [Qemu-devel] [PULL v2 0/3] Monitor patches for 2018-10-30

[Peter Maydell]

On 6 November 2018 at 17:39, Markus Armbruster <armbru@redhat.com> wrote:
> The following changes since commit 0ca70f19c010ccf0b10cf7cc1d2b9a87193fe787:
>
>   tests: Fix Python 3 detection on older GNU make versions (2018-11-06 14:58:13 +0000)
>
> are available in the Git repository at:
>
>   git://repo.or.cz/qemu/armbru.git tags/pull-monitor-2018-10-30-v2
>
> for you to fetch changes up to 0c57893d62596d1d91779452be3b38b4b72ecd04:
>
>   vl: Avoid crash when -mon is underspecified (2018-11-06 17:03:29 +0100)
>
> ----------------------------------------------------------------
> Monitor patches for 2018-10-30
>
> * Fix crash on shutdown with --daemonize
> * Avoid crash when -mon lacks chardev=...
>
> ----------------------------------------------------------------

Applied, thanks.

-- PMM