Upon fork, child was created in a new space but as a copy of any
cloned thread in the parent space. This was due to the search of forker thread
by its space id (which is shared among many cloned threads).
Now fixed.
modified: src/api/thread.c
modified: tasks/mm0/src/task.c
- Test0 has a full ipc mr read/write test.
- A full ipc occurs for definite only if both parties use the FULL IPC flag.
Otherwise the thread that makes the ipc copy rules on whether it was a short
or a full copy.
- Added a full ipc send/recv test
- Removed non-zero value checking in r2 for ipc that was there
to catch inadvertent full ipc calls.
- Added correct hanlding for read/write mrs for current status of utcb.
TODO:
- Add mapping of every utcb to every task for privileged access so that
the kernel can access every utcb without switching spaces.
- Removal of same mappings
- Upon thread creation need to copy page tables accordingly i.e.
each task will have its own utcb mapped with USER access, but every
other utcb as kernel access only. Need to handle this case upon page
table copying.
- Proper releasing of user pmd and pgds when a space is not used.
- Proper releasing of task, space ids.
- At occasions a starting thread gets bogus SPSR, this needs investigating.
- At a very rare occasion arch_setup_new_thread() had a kernel data abort during
register copying from one task to another. Needs investigating.
- Fixed potential concurrency bugs due to preemption being enabled.
- Introduced a new address space structure to better account for
address spaces and page tables.
- Currently executes fine up to forking. Will investigate.
- KIP's pointer to UTCB seems to work with existing l4lib ipc functions.
- Works up to clone()
- In clone we mmap() the same UTCB on each new thread - excessive.
- Generally during page fault handling, cloned threads may fault on the same page
multiple times even though a single handling would be enough for all of them.
Need to detect and handle this.
Added setting of utcb address to l4_thread_control.
This is going to be moved to exchange_registers() since we need to pass
both the utcb physical and virtual address and exregs fits such context
modification better than thread_control.
- Directory creation, file read/write is OK.
- Cannot reuse old task's fds. They are not recycled for some reason.
- Problems with fork/clone/exit. They fail for a reason.
It turned out we used one version of kmalloc for malloc() and another for kfree()!
Now fixed.
Added parent-child relationship to tasks. Need to polish handling CLONE_PARENT and THREAD.
A new or forked thread will have its tgid same as its unique thread id.
A cloned thread (i.e. in the same space) will get its parent's tgid if
the parent tgid is supplied as the suggested tgid in the ids field. Otherwise
the thread will have its tgid same as its unique thread id.
Previously we also allocated a tgid from a separate pool, but this doesn't
make sense. It is cleaner to have the unique thread id get used also as the tgid.
l4_unmap now returns -1 if given range was only partially unmapped.
do_munmap() now only unmaps address ranges that have correspondence in
the unmapped vmas. Trying to unmap regions with no correspondent vmas
causes problems in corner cases, e.g. mm0 that tries to mmap its own
address space during initialisation would unmap its whole address space
and fail to execute.
- Implemented reasonable way to suspend task.
- A task that has a pending suspend would be interrupted
from its sleep via the suspender task.
- If suspend was raised and right after, task became about to sleep,
then scheduler wakes it up.
- If suspend was raised when task was in user mode, then an irq suspends it.
- Also suspends are checked at the end of a syscall so that if suspend was
raised because of a syscall from the task, the task is suspended before it
goes back to user mode.
- This mechanism is very similar to signals, and it may lead as a base for
implementing signal handling.
- Implemented common vma dropping for shadow vm object dropping and task exiting.
- 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.)
- test0 now forks 16 tasks that each modify a global variable.
- scheduler now gives 1/10th of a second per task. It also does not increase timeslice
of a task that has scheduled.
- When a memory is granted to the kernel, the distribution of this memory to memcaches
was calculated in a complicated way. This is now simplified.
- 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.
Stopped working on self_spawn() - going to finish clone() syscall first.
Arch-specific clone() library call that does ipc() and cloned child setup.
- Need to finish thread_create() that satisfy clone() necessities. i.e. setting up its stack.
Question: Does the pager (and thus the microkernel) have to explicitly set SP_USR?
Once the call is known to be successful, the library could set it.
Child needs rewound function stack in order to reach registers r9-r12
that have original userspace values. But we jump to return_from_syscall
without rewinding the stack. Therefore to ease context restore, we save
r9-r12 on the stack as well upon syscall entry.
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.
serving mm0, if it page faults, system deadlocks because mm0 is waiting to be served by vfs.
FIX: To fix this, mm0 will need to fork itself and keep a separate thread solely for
page fault handling.
sys_timer accumulates timer ticks into seconds, minutes, hours and days.
It's left to the user to calculate from days into a date. It is not yet
known if the calculation is even roughly correct.
Reduced 2 kmem_reclaim/grant calls into one kmem_control call.
