data structure called kse_upcall to manage UPCALL. All KSE binding
and loaning code are gone.
A thread owns an upcall can collect all completed syscall contexts in
its ksegrp, turn itself into UPCALL mode, and takes those contexts back
to userland. Any thread without upcall structure has to export their
contexts and exit at user boundary.
Any thread running in user mode owns an upcall structure, when it enters
kernel, if the kse mailbox's current thread pointer is not NULL, then
when the thread is blocked in kernel, a new UPCALL thread is created and
the upcall structure is transfered to the new UPCALL thread. if the kse
mailbox's current thread pointer is NULL, then when a thread is blocked
in kernel, no UPCALL thread will be created.
Each upcall always has an owner thread. Userland can remove an upcall by
calling kse_exit, when all upcalls in ksegrp are removed, the group is
atomatically shutdown. An upcall owner thread also exits when process is
in exiting state. when an owner thread exits, the upcall it owns is also
removed.
KSE is a pure scheduler entity. it represents a virtual cpu. when a thread
is running, it always has a KSE associated with it. scheduler is free to
assign a KSE to thread according thread priority, if thread priority is changed,
KSE can be moved from one thread to another.
When a ksegrp is created, there is always N KSEs created in the group. the
N is the number of physical cpu in the current system. This makes it is
possible that even an userland UTS is single CPU safe, threads in kernel still
can execute on different cpu in parallel. Userland calls kse_create to add more
upcall structures into ksegrp to increase concurrent in userland itself, kernel
is not restricted by number of upcalls userland provides.
The code hasn't been tested under SMP by author due to lack of hardware.
Reviewed by: julian
for the disklabel: This facility is OBE.
First of all, we cannot sensibly implement this in a properly stacked
environment.
Second, if we did, it would confuse the heck out of users who
wouldn't be able to "start from scratch" by dd(8)'ing /dev/zero
onto /dev/da0.
Third, the offered protection is not comprehensive: no other software
would respect it.
Fourth and finally, the disklabel is already protected against
tampering if it controls open partitions.
Uselessness of these options discussed with: peter
a NULL filename argument allows a stream's mode to be changed. At the
moment it just recycles the old file descriptor instead of storing the
filename somewhere and using that to reopen the file, as the standard
seems to require. Strictly conforming C99 applications probably can't
tell the difference but POSIX ones can.
PR: 46791
functions implemented approximately the same limits on fragment memory
usage, but in different fashions.)
End user visible changes:
- Fragment reassembly queues are freed in a FIFO manner when maxfragpackets
has been reached, rather than all reassembly stopping.
MFC after: 5 days
physical memory. The default is still 2x physical memory. The nominal
calculation is used to back-off swap auto-allocation ('A'uto command)
when the disk is not large enough to accomodate all filesystem auto-defaults.
This gives other partitions (like /usr) more priority over swap on smaller
disks.
This should help solve reported auto-sizing failures on machines with small
hard drives and huge amounts of memory. For example, a machine with 2G of
disk and 4G of memory will fail to auto-size without this fix.
MFC after: 3 days
