Re: [Qemu-devel] [RFC][PATCH]Add timestamp to error message

[Markus Armbruster]

Seiji Aguchi <address@hidden> writes:

>> > Are gmtime() + strftime() unsuitable for some reason?
>> 
>> They are not async-signal safe, so they are not usable in between a
>> fork() and exec*().  Libvirt avoids them because it DOES log
>> information including timestamps in between fork/exec (and prior to
>> writing libvirt's virtime.c, we DID hit cases where libvirt would
>> deadlock a child process due to the non-safe use of a more naive
>> timestamp generator), but I don't know if qemu suffers from the same
>> restriction of when it has anything worth logging.
>
> In my understanding, gmtime() + strftime() is usable in error_report()
> because it seems to be called
> For just a option check.

error_report() is not bound to a particular task.  It simply reports
either to the current monitor or to stderr.  It's certainly not usuable
in a signal handler, or similar signal-unsafe context.

>>[TODO]
>>Other functions below are used to output error messages in qemu.
>  >- qerror_report() is called in many source codes.
>  >- fprintf() is called in vl.c.
>
> On the other hand, qerror_report() and fprintf () seems to be called
> in signal handers.

fprintf() in a signal handler?  Where?

> So, in those cases, some signal-safe functions should be used.