need some debugging help

[Terry Lambert]

Pawel Jakub Dawidek wrote:
> On Mon, Sep 01, 2003 at 12:48:41AM -0600, Kenneth D. Merry wrote:
> +>  - I tried just holding a mutex all the time, but obviously you can't
> +>    malloc while holding a mutex (except Giant), and the sysctl code does a
> +>    number of mallocs.  (The original cause of this problem -- M_WAITOK
> +>    mallocs.)
> 
> I've proposed some time ago changing M_WAITOK to M_NOWAIT, because
> function/macros responsible for sysctl creation could failed from other
> reasons, so I don't see any reason why they couldn't fail because of
> insufficient memory. Caller is obliged to check return value...

M_WAITOK is obliged to wait for fricking ever if it can't allocate
the memory, rather than failing and returning a NULL pointer that
then gets dereferenced because the function returned when the code
expected the traditional M_WAITOK semantics.

In other words, this problem derives from a semantics change, not
from any actual bug.

If you don't like it, then you need to change every instance of a
call to malloc with M_WAITOK to check its return value before using
it.  Doing this does'nt require introducing yet another semantic.

-- Terry