sbrk(2) broken

Kostik Belousov kostikbel at gmail.com
Fri Jan 4 05:48:40 PST 2008


On Fri, Jan 04, 2008 at 02:12:50PM +0100, Dag-Erling Sm??rgrav wrote:
> "Igor Mozolevsky" <igor at hybrid-lab.co.uk> writes:
> > This makes memory management in the userland hideously and
> > unnecessarily complicated. It's simpler to have SIGDANGER [...]
> 
> You don't seem to understand what Poul-Henning was trying to point out,
> which is that broadcasting SIGDANGER can make a bad situation much, much
> worse by waking up and paging in every single process in the system,
> including processes that are blocked and wouldn't otherwise run for
> several minutes, hours or even days (getty, inetd, sshd, mountd, even
> nfsd / nfsiod in some cases can sleep for days at a time waiting for
> I/O)

By making the default action for SIGDANGER to be SIG_IGN, this problem
would be mostly solved. Only processes that actually care about SIGDANGER
and installing the handler for it would require some non-trivial and
resource-hungry operation.
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