callout is first initialised, using a new function callout_init_mtx().
The callout system will acquire this mutex before calling the callout
function and release it on return.
In addition, the callout system uses the mutex to avoid most of the
complications and race conditions inherent in asynchronous timer
facilities, so mutex-protected callouts have much simpler semantics.
As long as the mutex is held when invoking callout_stop() or
callout_reset(), then these functions will guarantee that the callout
will be stopped, even if softclock() had already begun to process
the callout.
Existing Giant-locked callouts will automatically pick up the new
race-free semantics. This should close a number of race conditions
in the USB code and probably other areas of the kernel too.
There should be no change in behaviour for "MP-safe" callouts; these
still need to use the techniques mentioned in timeout(9) to avoid
race conditions.
when using the callout subsystem. Show how the callout_pending(),
callout_active() and callout_deactivate() macros can be used to
achieve simpler race-free callout semantics in many situations.
Reviewed by: Kame Project (including Itojun-san, Jinmei-san and Suzuki-san)
Approved by: Robert Watson (robert at freebsd dot org)
Obtained from: Kame Project and OpenBSD
Replace manual pages that may have violated the IETF's Copyright.
All come from the Kame tree.
Several were from OpenBSD except for ip6.4, and the inet6* pages which were
rewritten by me.
All of the text is new and drawn from reading the code and
documentation.
Approved by: Robert Watson (robert at freebsd dot org)
Remove files in preparation for replacement with totally new versions
of the manual pages.
Update the Makefile to handle the new file to be added.
location of a PCI device in the system chassis.
Remove the note about PAE.
Update document date.
Update my email address.
Update copyright.
MFC after: 1 week
