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[Qemu-devel] [PULL 3/6] ui/console: ensure do_safe_dpy_refresh holds BQL

From: Alex Bennée
Subject: [Qemu-devel] [PULL 3/6] ui/console: ensure do_safe_dpy_refresh holds BQL
Date: Tue, 28 Mar 2017 12:09:33 +0100

I missed the fact that when an exclusive work item runs it drops the
BQL to ensure all no vCPUs are stuck waiting for it, hence causing a
deadlock. However the actual helper needs to take the BQL especially
as we'll be messing with device emulation bits during the update which
all assume BQL is held.

We make a minor cpu_reloading_memory_map which must try and unlock the
RCU if we are actually outside the running context.

Reported-by: Laurent Desnogues <address@hidden>
Signed-off-by: Alex Bennée <address@hidden>
Reviewed-by: Paolo Bonzini <address@hidden>
Reviewed-by: Gerd Hoffmann <address@hidden>
 cpu-exec-common.c | 2 +-
 ui/console.c      | 2 ++
 2 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/cpu-exec-common.c b/cpu-exec-common.c
index 0504a9457b..e81da276bb 100644
--- a/cpu-exec-common.c
+++ b/cpu-exec-common.c
@@ -35,7 +35,7 @@ void cpu_loop_exit_noexc(CPUState *cpu)
 #if defined(CONFIG_SOFTMMU)
 void cpu_reloading_memory_map(void)
-    if (qemu_in_vcpu_thread()) {
+    if (qemu_in_vcpu_thread() && current_cpu->running) {
         /* The guest can in theory prolong the RCU critical section as long
          * as it feels like. The major problem with this is that because it
          * can do multiple reconfigurations of the memory map within the
diff --git a/ui/console.c b/ui/console.c
index 937c950840..dd27c9501b 100644
--- a/ui/console.c
+++ b/ui/console.c
@@ -1586,7 +1586,9 @@ bool dpy_gfx_check_format(QemuConsole *con,
 static void do_safe_dpy_refresh(CPUState *cpu, run_on_cpu_data opaque)
     DisplayChangeListener *dcl = opaque.host_ptr;
+    qemu_mutex_lock_iothread();
+    qemu_mutex_unlock_iothread();
 static void dpy_refresh(DisplayState *s)

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