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chardev: fix backend events regression with mux chardev

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Kirill noticied that on recent versions on QEMU he was not able to
trigger SysRq to invoke debug capabilites of Linux Kernel.  He tracked
it down to qemu_chr_be_event() ignoring CHR_EVENT_BREAK due s->be
being NULL. The bug was introduced in 2.8, commit a4afa548fc ("char:
move front end handlers in CharBackend"). Since the commit, the
qemu_chr_be_event() failed to deliver CHR_EVENT_BREAK due to
qemu_chr_fe_init() does not set s->be in case of mux.

Let's fix this by teaching mux to send an event to the frontend with
the focus.

Reported-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Fixes: a4afa548fc ("char: move front end handlers in CharBackend")
Message-Id: <20171103152824.21948-2-marcandre.lureau@redhat.com>
Tested-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Marc-André Lureau 2017-11-03 16:28:23 +01:00 • committed by Paolo Bonzini
parent 5a22ab7162
commit d09c4a4787
3 changed files with 23 additions and 6 deletions
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18
chardev/char.c
View file

@ -43,10 +43,19 @@ static Object *get_chardevs_root(void)
return container_get(object_get_root(), "/chardevs");
}
void qemu_chr_be_event(Chardev *s, int event)
static void chr_be_event(Chardev *s, int event)
{
CharBackend *be = s->be;
if (!be || !be->chr_event) {
return;
}
be->chr_event(be->opaque, event);
}
void qemu_chr_be_event(Chardev *s, int event)
{
/* Keep track if the char device is open */
switch (event) {
case CHR_EVENT_OPENED:
@ -57,11 +66,7 @@ void qemu_chr_be_event(Chardev *s, int event)
break;
}
if (!be || !be->chr_event) {
return;
}
be->chr_event(be->opaque, event);
CHARDEV_GET_CLASS(s)->chr_be_event(s, event);
}
/* Not reporting errors from writing to logfile, as logs are
@ -244,6 +249,7 @@ static void char_class_init(ObjectClass *oc, void *data)
ChardevClass *cc = CHARDEV_CLASS(oc);
cc->chr_write = null_chr_write;
cc->chr_be_event = chr_be_event;
}
static void char_finalize(Object *obj)