Re: [PATCH v2] Add VM info to improve error log message for qemu monitor

On 03/01/22 7:12 pm, Ani Sinha wrote: > > On Wed, 22 Dec 2021, Rohit Kumar wrote: > > > This patch is to determine the VM which had IO or socket hangup error. > > Accessing directly vm->def->name inside qemuMonitorIO() or > > qemuMonitorSend() > > might leads to illegal access as we are out of 'vm' context and vm->def > > might > > not exist. Adding a field "domainName" inside mon object to access vm name > > and initialising it when creating mon object. > The commit message should desribe the purpose of the change, not how it is > done. That can be easily understood reading the code. As for why the > implementation follows a particular way, we can explain it in the code > comments. > > This change adds the domain name in the error and debug logs during > monitor IO processing so that we may infer which VM experienced those > errors etc. This may help in debugging monitor IO errors. IMHO this > decription is enough. Thanks Ani, I will update the commit message in the next patch. > > > Signed-off-by: Rohit Kumar <rohit.kumar3(a)nutanix.com&gt; > > --- > > diff to v1: > > - Adding a field domainName inside _qemuMonitor struct for accessing vm > > name > > instead of directly accessing mon->vm->def->name. > > - Link to v1: > > https://urldefense.proofpoint.com/v2/url?u=https-3A__listman.redhat.com_a... > > - Talked with peter on RFC and he suggested me to add a field inside > > monitor struct to get VM name. > > > > src/qemu/qemu_monitor.c | 47 +++++++++++++++++++++++++---------------- > > 1 file changed, 29 insertions(+), 18 deletions(-) > > > > diff --git a/src/qemu/qemu_monitor.c b/src/qemu/qemu_monitor.c > > index dda6ae9796..c3a0227795 100644 > > --- a/src/qemu/qemu_monitor.c > > +++ b/src/qemu/qemu_monitor.c > > @@ -80,6 +80,7 @@ struct _qemuMonitor { > > GSource *watch; > > > > virDomainObj *vm; > > + char *domainName; > > > Here we can explain why we are adding an extra member as opposed to > referencing it directly. Right, we can access it directly. > > > qemuMonitorCallbacks *cb; > > void *callbackOpaque; > > @@ -243,6 +244,7 @@ qemuMonitorDispose(void *obj) > > virCondDestroy(&mon->notify); > > g_free(mon->buffer); > > g_free(mon->balloonpath); > > + g_free(mon->domainName); > > } > > > > > > @@ -530,13 +532,18 @@ qemuMonitorIO(GSocket *socket G_GNUC_UNUSED, > > qemuMonitor *mon = opaque; > > bool error = false; > > bool hangup = false; > > + virDomainObj *vm = NULL; > > + char *vmName = NULL; > > > These initializations are redundant since ... Acknowledged. > > virObjectRef(mon); > > > > + vm = mon->vm; > > + vmName = mon->domainName; > you initialize them here anyway. I will remove these in next patch. > > > + > > /* lock access to the monitor and protect fd */ > > virObjectLock(mon); > > #if DEBUG_IO > > - VIR_DEBUG("Monitor %p I/O on socket %p cond %d", mon, socket, cond); > > + VIR_DEBUG("Monitor %p I/O on socket %p cond %d vm=%p name=%s", mon, > > socket, cond, vm, NULLSTR(vmName)); > > #endif > > if (mon->fd == -1 || !mon->watch) { > > virObjectUnlock(mon); > > @@ -583,8 +590,8 @@ qemuMonitorIO(GSocket *socket G_GNUC_UNUSED, > > > > if (!error && !mon->goteof && > > cond & G_IO_ERR) { > > - virReportError(VIR_ERR_INTERNAL_ERROR, "%s", > > - _("Invalid file descriptor while waiting for > > monitor")); > > + virReportError(VIR_ERR_INTERNAL_ERROR, > > + _("%s: Invalid file descriptor while waiting > > for monitor"), NULLSTR(vmName)); > As per > https://urldefense.proofpoint.com/v2/url?u=https-3A__libvirt.org_coding-2... > , please > enclose %s within quotes: > _("'%s': Invalid file descriptor while waiting for monitor") Ack. Thanks. > > mon->goteof = true; > > } > > } > > @@ -609,13 +616,14 @@ qemuMonitorIO(GSocket *socket G_GNUC_UNUSED, > > virResetLastError(); > > } else { > > if (virGetLastErrorCode() == VIR_ERR_OK && !mon->goteof) > > - virReportError(VIR_ERR_INTERNAL_ERROR, "%s", > > - _("Error while processing monitor IO")); > > + virReportError(VIR_ERR_INTERNAL_ERROR, > > + _("%s: Error while processing monitor > > IO"), NULLSTR(vmName)); > Ditto. Ack. > > virCopyLastError(&mon->lastError); > > virResetLastError(); > > } > > > > - VIR_DEBUG("Error on monitor %s", > > NULLSTR(mon->lastError.message)); > > + VIR_DEBUG("Error on monitor %s mon=%p vm=%p name=%s", > > + NULLSTR(mon->lastError.message), mon, vm, > > NULLSTR(vmName)); > > /* If IO process resulted in an error & we have a message, > > * then wakeup that waiter */ > > if (mon->msg && !mon->msg->finished) { > > @@ -631,22 +639,22 @@ qemuMonitorIO(GSocket *socket G_GNUC_UNUSED, > > * will try to acquire the virDomainObj *mutex next */ > > if (mon->goteof) { > > qemuMonitorEofNotifyCallback eofNotify = mon->cb->eofNotify; > > - virDomainObj *vm = mon->vm; > > > > /* Make sure anyone waiting wakes up now */ > > virCondSignal(&mon->notify); > > virObjectUnlock(mon); > > - VIR_DEBUG("Triggering EOF callback"); > > + VIR_DEBUG("Triggering EOF callback mon=%p vm=%p name=%s", > > + mon, vm, NULLSTR(vmName)); > > (eofNotify)(mon, vm, mon->callbackOpaque); > > virObjectUnref(mon); > > } else if (error) { > > qemuMonitorErrorNotifyCallback errorNotify = > > mon->cb->errorNotify; > > - virDomainObj *vm = mon->vm; > > > > /* Make sure anyone waiting wakes up now */ > > virCondSignal(&mon->notify); > > virObjectUnlock(mon); > > - VIR_DEBUG("Triggering error callback"); > > + VIR_DEBUG("Triggering error callback mon=%p vm=%p name=%s", > > + mon, vm, NULLSTR(vmName)); > > (errorNotify)(mon, vm, mon->callbackOpaque); > > virObjectUnref(mon); > > } else { > > @@ -694,6 +702,7 @@ qemuMonitorOpenInternal(virDomainObj *vm, > > mon->fd = fd; > > mon->context = g_main_context_ref(context); > > mon->vm = virObjectRef(vm); > > + mon->domainName = g_strdup(vm->def->name); > do not forget to g_free() this during cleanup in the same function. So, in cleanup: qemuMonitorDispose is called. And there I have added g_free() to clean mon->domainName.

> > > mon->waitGreeting = true; > > mon->cb = cb; > > mon->callbackOpaque = opaque; > > @@ -932,17 +941,19 @@ qemuMonitorSend(qemuMonitor *mon, > > qemuMonitorMessage *msg) > > { > > int ret = -1; > > + virDomainObj *vm = mon->vm; > > + char *vmName = mon->domainName; > > > > /* Check whether qemu quit unexpectedly */ > > if (mon->lastError.code != VIR_ERR_OK) { > > - VIR_DEBUG("Attempt to send command while error is set %s", > > - NULLSTR(mon->lastError.message)); > > + VIR_DEBUG("Attempt to send command while error is set %s mon=%p > > vm=%p name=%s", > > + NULLSTR(mon->lastError.message), mon, vm, > > NULLSTR(vmName)); > > virSetError(&mon->lastError); > > return -1; > > } > > if (mon->goteof) { > > - virReportError(VIR_ERR_INTERNAL_ERROR, "%s", > > - _("End of file from qemu monitor")); > > + virReportError(VIR_ERR_INTERNAL_ERROR, > > + _("%s: End of file from qemu monitor"), > > NULLSTR(vmName)); > ditto re error string format. Ack. > > > return -1; > > } > > > > @@ -955,15 +966,15 @@ qemuMonitorSend(qemuMonitor *mon, > > > > while (!mon->msg->finished) { > > if (virCondWait(&mon->notify, &mon->parent.lock) < 0) { > > - virReportError(VIR_ERR_INTERNAL_ERROR, "%s", > > - _("Unable to wait on monitor condition")); > > + virReportError(VIR_ERR_INTERNAL_ERROR, > > + _("%s: Unable to wait on monitor condition"), > > NULLSTR(vmName)); > ditto as above. Ack. > > goto cleanup; > > } > > } > > > > if (mon->lastError.code != VIR_ERR_OK) { > > - VIR_DEBUG("Send command resulted in error %s", > > - NULLSTR(mon->lastError.message)); > > + VIR_DEBUG("Send command resulted in error %s mon=%p vm=%p > > name=%s", > > + NULLSTR(mon->lastError.message), mon, vm, > > NULLSTR(vmName)); > > virSetError(&mon->lastError); > > goto cleanup; > > } > > -- > > 2.25.1 > > > >