Peter Pentchev <[EMAIL PROTECTED]> writes:
> Or rather, do not try this while syslogd is running.
>
> src/sys/kern/subr_log.c defines the operation of the /dev/klog
> device, and there is an upper limit on the number of processes
> that can simultaneously open the log device - the limit is one.
> That is, while syslogd is running, no other process can open
> the klog device for reading.
>
> This seems to have been the case ever since rev. 1.1 of
> src/sys/kern/subr_log.c; that is, this has been the case
> in 4.4BSD and earlier. Anybody have any recollection
> on why the kernel won't let more than one process intercept
> log messages (aside from the obvious fact that stacked syslogd's
> could easily DoS a machine)?
Take a look at how it spits out those messages and you'll see why. In
short, if you have two processes reading them, neither will get the
full set because a read advances the read pointer (msgbufp->bufp,
IIRC). This can't easily be fixed.
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