On Mon, Apr 30, 2001 at 12:07:44PM -0700, David S. Miller wrote:
> Even more effective is:
>
> mv /wherever/exeimage /usr/bin/exeimage
>
> The kernel keeps around the contents of the old file while
> the executing process still runs.
>
> This is also basically how things like libc get installed.
> A single mv is not only preserves currently referenced contents,
> it is atomic.
But something must have been not working with it for mmaps/shlibs
(not executables); at least historically.
At least I remember that all hell broke lose when you tried to update
libc by cp'ing a new one to /lib/libc.so in the 1.2 days. cp should create a
new inode (it uses O_CREAT) so in theory it should be coherent by the inode
reference; but somehow it didn't use to work and random already running
programs started to segfault. This was long ago. I wonder if old
GNU cp used O_TRUNC instead of O_CREAT, or was there some other kernel bug
with mappings (hopefully long since fixed). Anybody remembers?
-Andi
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