Re: [Qemu-devel] [PATCH] oslib: make error handling more reasonable

[Anthony Liguori]

On 02/13/2012 08:04 AM, Markus Armbruster wrote:
> Stefan Weil<address@hidden>  writes:
>
> > Am 10.02.2012 16:13, schrieb Zhi Yong Wu:
> > > On Fri, Feb 10, 2012 at 10:41 PM, Daniel P. Berrange
> > > <address@hidden>  wrote:
> > > > On Fri, Feb 10, 2012 at 10:34:13PM +0800, Zhi Yong Wu wrote:
> > > > > From: Zhi Yong Wu<address@hidden>
> > > > >
> > > > > Signed-off-by: Zhi Yong Wu<address@hidden>
> > > > > ---
> > > > >   oslib-posix.c |    4 ++--
> > > > >   oslib-win32.c |    4 ++--
> > > > >   2 files changed, 4 insertions(+), 4 deletions(-)
> > > > >
> > > > > diff --git a/oslib-posix.c b/oslib-posix.c
> > > > > index b6a3c7f..f978d56 100644
> > > > > --- a/oslib-posix.c
> > > > > +++ b/oslib-posix.c
> > > > > @@ -80,7 +80,7 @@ void *qemu_oom_check(void *ptr)
> > > > >   {
> > > > >       if (ptr == NULL) {
> > > > >           fprintf(stderr, "Failed to allocate memory: %s\n",
> > > > > strerror(errno));
> > > > > -        abort();
> > > > > +        exit(EXIT_FAILURE);
> > > >
> > > > exit() will call any atexit()/on_exit() handlers, as well as trying
> > > > to flush I/O streams. Any of these actions may require further
> > > > memory allocations, which will likely fail, or worse cause this
> > > > code to re-enter itself if an atexit() handler calls qemu_malloc
> > > Nice, very reasonable.
> > > > The only option other than abort(), is to use  _Exit() which
> > > > doesn't try to run cleanup handlers.
> > > I will try to send out v2
> >
> > Could you please explain why calling exit, _Exit or _exit is more
> > reasonable than calling abort?
> >
> > abort can create core dumps or start a debugger which is
> > useful for me and maybe other developers, too.
>
> I consider abort() on OOM somewhat eccentric.  abort() is for
> programming errors.  Resource shortage is an environmental error that is
> sometimes (but not always) caused by a programming error.
>
> I'd rather inconvenience programmers (by making it a little bit harder
> to debug programming errors that cause OOM) than confuse users with
> inappropriate scary "crashes".

OOM is a going to 99% of the time be a bug in QEMU.

For the rare exceptions (like a bad -m argument), we should handle those as 
special cases.

Regards,

Anthony Liguori

>