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

[Anthony Liguori <anthony@codemonkey.ws>]

On 02/13/2012 08:04 AM, Markus Armbruster wrote:
> Stefan Weil<sw@weilnetz.de>  writes:
>
>> Am 10.02.2012 16:13, schrieb Zhi Yong Wu:
>>> On Fri, Feb 10, 2012 at 10:41 PM, Daniel P. Berrange
>>> <berrange@redhat.com>  wrote:
>>>> On Fri, Feb 10, 2012 at 10:34:13PM +0800, Zhi Yong Wu wrote:
>>>>> From: Zhi Yong Wu<wuzhy@linux.vnet.ibm.com>
>>>>>
>>>>> Signed-off-by: Zhi Yong Wu<wuzhy@linux.vnet.ibm.com>
>>>>> ---
>>>>>   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

>