write lock when doing PID allocation, and during the process exit path.
Use a read lock every where else, including within schedcpu() (interrupt
context). Note that holding the write lock implies blocking schedcpu()
from running (blocks softclock).
PID allocation is now MP-safe.
Note this actually fixes a bug on single processor systems that was probably
extremely difficult to tickle; it was possible that schedcpu() would run
off a bad pointer if the right clock interrupt happened to come in the
middle of a LIST_INSERT_HEAD() or LIST_REMOVE() to/from allproc.
the child inherits the stack pointer from the parent (traditional
behavior). Like the signal stack, the stack area is secified as
a low address and a size; machine-dependent code accounts for stack
direction.
This is required for clone(2).
parent, specified at fork time. Specify a new flag to wait4(2), WALTSIG,
to wait for processes which use an alternate exit signal.
This is required for clone(2).
- no longer conditionalized
- when traced, charge time to real parent, not debugger
- make it clear for future rototillers that p_estcpu should be moved
to the "copy" region of struct proc.
kthread_create(). Implement kthread_exit() (causes a thrad to exit).
Set P_NOCLDWAIT on kernel threads, which will cause any of their children
to be reparented to init(8) (which is already prepared to wait out orphaned
processes).
in the future):
- New function, fork_kthread(), takes entry point, argument for entry point,
and comment for new proc. May be called by any context, will fork the
thread from proc0 (requires slight changes to cpu_fork()).
- cpu_set_kpc() now takes a third argument, a void *arg to pass to the
thread entry point. Thread entry point now takes void * instead of
struct proc *.
- Create the pagedaemon and reaper kernel threads using fork_kthread().
the new proc structure when performing a fork. This makes it much
easier to abort a fork operation and return an error if we run out
of KVA space.
The U-area pages are still wired down in {,u}vm_fork(), as before.
(thus causing s_leader to become NULL) by storing the session ID separately
in the session structure. Export the session ID to userspace in the
eproc structure.
Submitted by Tom Proett <proett@nas.nasa.gov>.
UVM was written by chuck cranor <chuck@maria.wustl.edu>, with some
minor portions derived from the old Mach code. i provided some help
getting swap and paging working, and other bug fixes/ideas. chuck
silvers <chuq@chuq.com> also provided some other fixes.
this is the rest of the MI portion changes.
this will be KNF'd shortly. :-)
3BSD vfork(2), i.e. share address space w/ parent and block parent.
Keep statistics on the total number of forks, the number of forks that
block the parent, and the number of forks that share the address space
with the parent.
