- for better readability xpp is substitued by sender
- makes sure that the dequeued sender has p_q_link == NULL and that
this condition holds when enqueuing the sender again. This is a
sanity check to make sure that the new sender is not enqueued
already
- Before this change the dequeued sender's p_q_link may not be NULL
and it was only set to NULL when enqueued again
- removes p_delivermsg_lin item from the process structure and code
related to it
- as the send part, the receive does not need to use the
PHYS_COPY_CATCH() and umap_local() couple.
- The address space of the target process is installed before
delivermsg() is called.
- unlike the linear address, the virtual address does not change when
paging is turned on nor after fork().
- FPU context is stored only if conflict between 2 FPU users or while
exporting context of a process to userspace while it is the active
user of FPU
- FPU has its owner (fpu_owner) which points to the process whose
state is currently loaded in FPU
- the FPU exception is only turned on when scheduling a process which
is not the owner of FPU
- FPU state is restored for the process that generated the FPU
exception. This process runs immediately without letting scheduler
to pick a new process to resolve the FPU conflict asap, to minimize
the FPU thrashing and FPU exception hadler execution
- faster all non-FPU-exception kernel entries as FPU state is not
checked nor saved
- removed MF_USED_FPU flag, only MF_FPU_INITIALIZED remains to signal
that a process has used FPU in the past
There seems to have been a broken assumption in the fpu context
restoring code. It restores the context of the running process, without
guarantee that the current process is the one that will be scheduled.
This caused fpu saving for a different process to be triggered without
fpu hardware being enabled, causing an fpu exception in the kernel. This
practically only shows up with DEBUG_RACE on. Fix my thruby+me.
The fix
. is to only set the fpu-in-use-by-this-process flag in the
exception handler, and then take care of fpu restoring when
actually returning to userspace
And the patch
. translates fpu saving and restoring to c in arch_system.c,
getting rid of a juicy chunk of assembly
. makes osfxsr_feature private to arch_system.c
. removes most of the arch dependent code from do_sigsend
- substituted the use of the m_source message field by
caller->p_endpoint in kernel calls. It is the same information, just
passed more intuitively.
- the last dependency on m_type field is removed.
- do_unused() is substituted by a check for NULL.
- this pretty much removes the depency of kernel calls on the general
message format. In the future this may be used to pass the kcall
arguments in a different structure or registers (x86-64, ARM?) The
kcall number may be passed in a register already.
- removes dependency of do_safecopy() on the m_type field of the kcall
messages.
- instead of do_safecopy() figuring out what action is requested, the
correct safecopy method is called right away.
- Currently the cpu time quantum is timer-ticks based. Thus the
remaining quantum is decreased only if the processes is interrupted
by a timer tick. As processes block a lot this typically does not
happen for normal user processes. Also the quantum depends on the
frequency of the timer.
- This change makes the quantum miliseconds based. Internally the
miliseconds are translated into cpu cycles. Everytime userspace
execution is interrupted by kernel the cycles just consumed by the
current process are deducted from the remaining quantum.
- It makes the quantum system timer frequency independent.
- The boot processes quantum is loosely derived from the tick-based
quantas and 60Hz timer and subject to future change
- the 64bit arithmetics is a little ugly, will be changes once we have
compiler support for 64bit integers (soon)
-Makefile updates
-Update mkdep
-Build fixes/warning cleanups for some programs
-Restore leading underscores on global syms in kernel asm files
-Increase ramdisk size
ask to map in oxpcie i/o memory and support serial i/o for it in the
kernel. set oxpcie=<address> in boot monitor (retrieve address using
pci_debug=1 output). (no sanity checking is done on the address
currently.) disabled by default.
The change also contains some other minor cleanup (a new serial.h to set
register info common to UART and the OXPCIe card, in-kernel memory
mapping a little more structured and env_get() to get sysenv variables
without knowing about the params_buffer).
In this second phase, scheduling is moved from PM to its own
scheduler (see r6557 for phase one). In the next phase we hope to a)
include useful information in the "out of quantum" message and b)
create some simple scheduling policy that makes use of that
information.
When the system starts up, PM will iterate over its process table and
ask SCHED to take over scheduling unprivileged processes. This is
done by sending a SCHEDULING_START message to SCHED. This message
includes the processes endpoint, the parent's endpoint and its nice
level. The scheduler adds this process to its schedproc table, issues
a schedctl, and returns its own endpoint to PM - as the endpoint of
the effective scheduler. When a process terminates, a SCHEDULING_STOP
message is sent to the scheduler.
The reason for this effective endpoint is for future compatibility.
Some day, we may have a scheduler that, instead of scheduling the
process itself, forwards the SCHEDULING_START message on to another
scheduler.
PM has information on who schedules whom. As such, scheduling
messages from user-land are sent through PM. An example is when
processes change their priority, using nice(). In that case, a
getsetpriority message is sent to PM, which then sends a
SCHEDULING_SET_NICE to the process's effective scheduler.
When a process is forked through PM, it inherits its parent's
scheduler, but is spawned with an empty quantum. As before, a request
to fork a process flows through VM before returning to PM, which then
wakes up the child process. This flow has been modified slightly so
that PM notifies the scheduler of the new process, before waking up
the child process. If the scheduler fails to take over scheduling,
the child process is torn down and the fork fails with an erroneous
value.
Process priority is entirely decided upon using nice levels. PM
stores a copy of each process's nice level and when a child is
forked, its parent's nice level is sent in the SCHEDULING_START
message. How this level is mapped to a priority queue is up to the
scheduler. It should be noted that the nice level is used to
determine the max_priority and the parent could have been in a lower
priority when it was spawned. To prevent a CPU intensive process from
hawking the CPU by continuously forking children that get scheduled
in the max_priority, the scheduler should determine in which queue
the parent is currently scheduled, and schedule the child in that
same queue.
Other fixes: The USER_Q in kernel/proc.h was incorrectly defined as
NR_SCHED_QUEUES/2. That results in a "off by one" error when
converting priority->nice->priority for nice=0. This also had the
side effect that if someone were to set the MAX_USER_Q to something
else than 0, then USER_Q would be off.
- this patch only renames schedcheck() to switch_to_user(),
cycles_accounting_stop() to context_stop() and restart() to
+restore_user_context()
- the motivation is that since the introduction of schedcheck() it has
been abused for many things. It deserves a better name. It should
express the fact that from the moment we call the function we are in
the process of switching to user.
- cycles_accounting_stop() was originally a single purpose function.
As this function is called at were convenient places it is used in
for other things too, e.g. (un)locking the kernel. Thus it deserves
a better name too.
- using the old name, restart() does not call schedcheck(), however
calls to restart are replaced by calls to schedcheck()
[switch_to_user] and it calls restart() [restore_user_context]
it does this by
- making all processes interruptible by running out of quantum
- giving all processes a single tick of quantum
- picking a random runnable process instead of in order, and
from a single pool of runnable processes (no priorities)
This together with very high HZ values currently provokes some race conditions
seen earlier only when running with SMP.
- this patch substitutes *xpp for sender to increase readability of
mini_receive().
- makes sure that the dequeued sender has p_q_link == NULL and that
this condition holds when enqueuing the sender again.
- it is a sanity check to make sure that the new sender is not
enqueued already. Before this change the dequeued sender's p_q_link
may not be NULL and it was only set to NULL when enqueued again.
