[libvirt] [PATCHv2] qemu: agent: Fix QEMU guest agent is not available due to an error

These days, we experienced one qemu guest agent is not available error. Then the guest agent couldn't be used forever before rebooting the libvirtd daemon or reboot the qemu-guest-agent in the VM(you can also reboot the VM) to clear the priv->agentError. This is one bug for a long time in many verisons of libvirtd: https://bugzilla.redhat.com/show_bug.cgi?id=1090551 And there is one python script to reproduce this bug from the bugzilla: https://github.com/aspirer/study/blob/master/qemu-guest-agent/test2.py Just set the timeout to 0 at Line26, you can reproduce it very quickly: rsp = libvirt_qemu.qemuAgentCommand(dom, cmd, 1, 0) // 1 -> 0 The reason why this could happen is that: In case we received something like {"return": {}} for example, it is likely that somebody: 1) Started GA thread which sent one "guest-ping" command with seconds equals to VIR_DOMAIN_QEMU_AGENT_COMMAND_NOWAIT(0) makes this function return immediately without waiting, but after updating the events, it will sleep in virCondWait() or virCondWaitUntil(). 2) While in AgentIO thread the "guest-ping" command is sent successfully, with updating the events it will wait for reply. 3) Then the GA thread is woken up and the mon->msg is set to NULL and exit. 4) At last the AgentIO thread receives the reply of "guest-ping" command with the mon->msg == NULL. This case could be adapt to all the GA commands, including guest-sync, etc. This patch will check if this is the case and don't report an error but return silently. Signed-off-by: Xiubo Li <lixiubo(a)cmss.chinamobile.com&gt; Signed-off-by: Zhuoyu Zhang <zhangzhuoyu(a)cmss.chinamobile.com&gt; Signed-off-by: Wei Tang <tangwei(a)cmss.chinamobile.com&gt; Signed-off-by: Yaowei Bai <baiyaowei(a)cmss.chinamobile.com&gt; Signed-off-by: Qide Chen <chenqide(a)cmss.chinamobile.com&gt; --- Changes in V2: - check value type instead of object type. src/qemu/qemu_agent.c | 37 ++++++++++++++++++++++++++++--------- src/util/virjson.h | 7 +++++++ 2 files changed, 35 insertions(+), 9 deletions(-) diff --git a/src/qemu/qemu_agent.c b/src/qemu/qemu_agent.c index eeede6b..f5408cc 100644 --- a/src/qemu/qemu_agent.c +++ b/src/qemu/qemu_agent.c @@ -308,7 +308,6 @@ qemuAgentIOProcessLine(qemuAgentPtr mon, { virJSONValuePtr obj = NULL; int ret = -1; - unsigned long long id; VIR_DEBUG("Line [%s]", line); @@ -333,16 +332,36 @@ qemuAgentIOProcessLine(qemuAgentPtr mon, obj = NULL; ret = 0; } else { - /* If we've received something like: - * {"return": 1234} - * it is likely that somebody started GA - * which is now processing our previous - * guest-sync commands. Check if this is - * the case and don't report an error but + virJSONValuePtr val; + + /* In case we received something like: + * {"return": {}} for example, + * it is likely that somebody: + * + * 1) Started GA thread which sent one "guest-ping" command + * with seconds equals to VIR_DOMAIN_QEMU_AGENT_COMMAND_NOWAIT(0) + * makes this function return immediately without waiting, but + * after updating the events, it will sleep in virCondWait() or + * virCondWaitUntil(). + * + * 2) While in AgentIO thread the "guest-ping" command is sent + * successfully, with updating the events it will wait for reply. + * + * 3) Then the GA thread is woken up and the mon->msg is set + * to NULL and exit. + * + * 4) At last the AgentIO thread receives the reply of "guest-ping" + * command with the mon->msg == NULL. + * + * This case could be adapt to all the GA commands, including + * guest-sync, etc. + * + * Check if this is the case and don't report an error but * return silently. */ - if (virJSONValueObjectGetNumberUlong(obj, "return", &id) == 0) { - VIR_DEBUG("Ignoring delayed reply to guest-sync: %llu", id); + val = virJSONValueObjectGet(obj, "return"); + if (val && virJSONValueTypeIsValid(val)) { + VIR_DEBUG("Ignoring delayed command reply"); ret = 0; goto cleanup; } diff --git a/src/util/virjson.h b/src/util/virjson.h index 66ed48a..cb1d973 100644 --- a/src/util/virjson.h +++ b/src/util/virjson.h @@ -80,6 +80,13 @@ struct _virJSONValue { } data; }; +static inline bool +virJSONValueTypeIsValid(virJSONValuePtr value) +{ + return ((value->type >= VIR_JSON_TYPE_OBJECT) && + (value->type <= VIR_JSON_TYPE_BOOLEAN)); +} + void virJSONValueFree(virJSONValuePtr value); int virJSONValueObjectCreate(virJSONValuePtr *obj, ...) -- 1.8.3.1