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[Qemu-devel] [PATCH 2/2] monitor: add proper reference counting of the c
From: |
Greg Kurz |
Subject: |
[Qemu-devel] [PATCH 2/2] monitor: add proper reference counting of the current CPU |
Date: |
Fri, 13 Oct 2017 10:35:31 +0200 |
User-agent: |
StGit/0.17.1-46-g6855-dirty |
If a CPU selected with the "cpu" command is hot-unplugged then "info cpus"
causes QEMU to exit:
(qemu) device_del cpu1
(qemu) info cpus
qemu:qemu_cpu_kick_thread: No such process
This happens because "cpu" stores the pointer to the selected CPU into
the monitor structure. When the CPU is hot-unplugged, we end up with a
dangling pointer. The "info cpus" command then does:
hmp_info_cpus()
monitor_get_cpu_index()
mon_get_cpu()
cpu_synchronize_state() <--- called with dangling pointer
This could cause a QEMU crash as well.
This patch switches the monitor to use object_ref() to ensure the
CPU object doesn't vanish unexpectedly. The reference is dropped
either when "cpu" is used to switch to another CPU, or when the
selected CPU is unrealized and cpu_list_remove() sets its cpu_index
back to UNASSIGNED_CPU_INDEX.
Signed-off-by: Greg Kurz <address@hidden>
---
monitor.c | 12 ++++++++++++
1 file changed, 12 insertions(+)
diff --git a/monitor.c b/monitor.c
index fe0d1bdbb461..1c0b9a2c3ad3 100644
--- a/monitor.c
+++ b/monitor.c
@@ -579,6 +579,9 @@ static void monitor_data_init(Monitor *mon)
static void monitor_data_destroy(Monitor *mon)
{
+ if (mon->mon_cpu) {
+ object_unref((Object *) mon->mon_cpu);
+ }
qemu_chr_fe_deinit(&mon->chr, false);
if (monitor_is_qmp(mon)) {
json_message_parser_destroy(&mon->qmp.parser);
@@ -1047,12 +1050,21 @@ int monitor_set_cpu(int cpu_index)
if (cpu == NULL) {
return -1;
}
+ if (cur_mon->mon_cpu) {
+ object_unref((Object *) cur_mon->mon_cpu);
+ }
cur_mon->mon_cpu = cpu;
+ object_ref((Object *) cpu);
return 0;
}
CPUState *mon_get_cpu(void)
{
+ if (cur_mon->mon_cpu &&
+ cur_mon->mon_cpu->cpu_index == UNASSIGNED_CPU_INDEX) {
+ object_unref((Object *) cur_mon->mon_cpu);
+ cur_mon->mon_cpu = NULL;
+ }
if (!cur_mon->mon_cpu) {
if (!first_cpu) {
return NULL;
Re: [Qemu-devel] [PATCH 0/2] monitor: increase the refcount of the current CPU, Cornelia Huck, 2017/10/13