Re: kernel 2.5: mlock broken?

[Andrew Morton]

Andreas Romeyke <art1@xxxxxxxxxxxxxxxx> wrote:
>
> Hi folks,
> 
> By testing 2.6.0-test2, I detected that the glibc-function mlock(),
> provided by /sys/mlock.h seems to be a deadlock in some cases on 2.5
> 
> If you want to lock more memory than physical RAM could be freed, the
> mlock() does not return with an errorcode as under 2.4.21 does.
> The system hangs around. This problem was catched under x86 and s390
> architecture by using Debian distribution (woody and unstable) and
> others  with the well known memtest program written by Charles Cazabon
> from   http://www.qcc.ca/~charlesc/software/memtester/ (ver. 2.93.1).
> 

2.4 kernels have a little check which prevents a single process from
mlocking more than half of physical memory.  So you need to run two
processes to kill a 2.4 box with mlock.

Some people want to be able to mlock more memory than that in a single
process, so the check was removed in 2.6.  It was pretty pointless.

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