- Updated sleeping paths such that a task is atomically put into
a runqueue and made RUNNABLE, or removed from a runqueue and made SLEEPING.
- Modified vma dropping sources to handle both copy_on_write() and exit() cases
in a common function.
- Added the first infrastructure to have a pager to suspend a task and wait for
suspend completion from the scheduler.
A new scheduler replaces the old one.
- There are no sched_xxx_notify() calls that ask scheduler to change task state.
- Tasks now have priorities and different timeslices.
- One second interval is distributed among processes.
- There are just runnable and expired queues.
- SCHED_GRANULARITY determines a maximum running boundary for tasks.
- Scheduler can now detect a safe point and suspend a task.
Interruptible blocking is implemented.
- Mutexes, waitqueues and ipc are modified to have an interruptible nature.
- Sleep information is stored on the ktcb. (which waitqueue? etc.)
- Fixed do_mmap() so that it returns mapped address, and various bugs.
- A child seems to fork with new setup, but with incorrect return value.
Need to use and test exregs() for fork + clone.
- Shmat searches an unmapped area if input arg is invalid, do_mmap()
should do this.
- Added mutex_trylock()
- Implemented most of exchange_registers()
- thread_control() now needs a lock for operations that can modify thread context.
- thread_start() does not initialise scheduler flags, now done in thread_create.
TODO:
- Fork/clone'ed threads should retain their context in tcb, not syscall stack.
- exchange_registers() calls in userspace need cleaning up.
This copies the parent kernel stack to child only for the part where
the previous context is saved. Then the child registers are modified
so that it would begin execution from returning of the system call.
Headers 3 headers related to message registers and utcbs are now merged under
utcb.h in libl4. Some message register definitions used by the kernel are now
moved into kernel's glue/message.h. This avoids the duplication of same
definitions. Also the total number of mregs are now determined by arch-specific
kernel header, which is good.
Removed previously implemented but untested mechanism of blocking tasks
from doing ipc to certain tasks using certain tags. This is to be considered
for future implementation.
