Skip to content

Commit

Permalink
Merge branch 'master' into lkt-docker-docs
Browse files Browse the repository at this point in the history
  • Loading branch information
@tavip
tavip authored Mar 3, 2020
2 parents 9a8bab0 + 96a0222 commit e5c318a
Show file tree
Hide file tree
Showing 2 changed files with 79 additions and 73 deletions.
142 changes: 71 additions & 71 deletions Documentation/teaching/labs/kernel_api.rst
View file
Original file line number Diff line number Diff line change
Expand Up @@ -650,12 +650,12 @@ cause of the error?

.. hint:: In the error message, follow the line containing the :c:macro:`BUG`
for a description of the error. You are not allowed to sleep in
atomic context. The atomic context is given by a section
between a lock operation and an unlock on a spinlock.
atomic context. The atomic context is given by a section
between a lock operation and an unlock on a spinlock.

.. note:: The
:c:func:`schedule_timeout` function, corroborated with the
:c:macro:`set_current_state` macro, forces the current process to wait
:c:macro:`set_current_state` macro, forces the current process to wait
for 5 seconds.

.. note:: Review the `Contexts of execution`_, `Locking` and `Spinlock`_
Expand Down Expand Up @@ -686,27 +686,27 @@ free them (in :c:func:`memory_exit`).
:c:type:`struct task_struct` structure, returned by :c:macro:`current`
macro.

.. hint::
Search for :c:type:`pid` in :c:type:`task_struct`.
.. hint::
Search for :c:type:`pid` in :c:type:`task_struct`.

* PID of the parent process of the current process.
* PID of the parent process of the current process.

.. hint::
Search for the relevant field from :c:type:`struct task_struct`
structure. Look after "parent".
.. hint::
Search for the relevant field from :c:type:`struct task_struct`
structure. Look after "parent".

* PID of the next process from the list of processes, relative to the
current process.
* PID of the next process from the list of processes, relative to the
current process.

.. hint::
Use :c:macro:`next_task` macro, which returns a pointer to the next
process (i.e a :c:type:`struct task_struct` structure).
.. hint::
Use :c:macro:`next_task` macro, which returns a pointer to the next
process (i.e a :c:type:`struct task_struct` structure).

* PID of the next process of the next process, relative to the current
process.
* PID of the next process of the next process, relative to the current
process.

.. hint::
Call 2 times the :c:macro:`next_task`.
.. hint::
Call 2 times the :c:macro:`next_task`.

3. (TODO 3) Display the four structures.
* Use :c:func:`printk` to display their two fields:
Expand All @@ -716,26 +716,26 @@ free them (in :c:func:`memory_exit`).
(use :c:func:`kfree`).

.. hint::
* You can access the current process using :c:macro:`current`
macro.
* Look for the relevant fields in the :c:type:`struct task_struct`
structure (:c:member:`pid`, :c:member:`parent`).
* Use the :c:macro:`next_task` macro. The macro returns the pointer to
the next process (ie. a :c:type:`struct task_struct*` structure).
* You can access the current process using :c:macro:`current`
macro.
* Look for the relevant fields in the :c:type:`struct task_struct`
structure (:c:member:`pid`, :c:member:`parent`).
* Use the :c:macro:`next_task` macro. The macro returns the pointer to
the next process (ie. a :c:type:`struct task_struct*` structure).

.. note:: The :c:type:`struct task_struct` structure contains two fields to
designate the parent of a task:

* :c:member:`real_parent` points to the process that created the
task or to process with pid 1 (init) if the parent
completed its execution.
* :c:member:`parent` indicates to the current task parent (the
process that will be reported if the task completes
execution).
* :c:member:`real_parent` points to the process that created the
task or to process with pid 1 (init) if the parent
completed its execution.
* :c:member:`parent` indicates to the current task parent (the
process that will be reported if the task completes
execution).

In general, the values of the two fields are the same, but
there are situations where they differ, for example when
using the :c:func:`ptrace` system call.
In general, the values of the two fields are the same, but
there are situations where they differ, for example when
using the :c:func:`ptrace` system call.

.. hint:: Review the `Memory allocation`_ section in the lab.

Expand All @@ -751,18 +751,18 @@ previous exercise into a list. The list will be built in the
loaded. The list will be printed and deleted in the :c:func:`list_exit`
function and the :c:func:`task_info_purge_list` function.

1. (TODO 1) Complete the :c:func:`task_info_add_to_list` function to allocate
a :c:type:`struct task_info` structure and add it to the list.
1. (TODO 1) Complete the :c:func:`task_info_add_to_list` function to allocate
a :c:type:`struct task_info` structure and add it to the list.

2. (TODO 2) Complete the :c:func:`task_info_purge_list` function to delete
all the elements in the list.
2. (TODO 2) Complete the :c:func:`task_info_purge_list` function to delete
all the elements in the list.

3. Compile the kernel module. Load and unload the module by
following the messages displayed by the kernel.
3. Compile the kernel module. Load and unload the module by
following the messages displayed by the kernel.

.. hint:: Review the labs `Lists`_ section. When deleting items from
the list, you will need to use either the
:c:macro:`list_for_each_safe` or :c:macro:`list_for_each_entry_safe`
the list, you will need to use either the
:c:macro:`list_for_each_safe` or :c:macro:`list_for_each_entry_safe`
macros.

5. Working with kernel lists for process handling
Expand All @@ -773,49 +773,49 @@ contents of the :file:`list-full.c` and notice comments marked with
``TODO``. In addition to the :file:`4-list` functionality we add the
following:

* A :c:member:`count` field showing how many times a process has been "added"
to the list.
* If a process is "added" several times, no new entry is created in
the list, but:
* A :c:member:`count` field showing how many times a process has been "added"
to the list.
* If a process is "added" several times, no new entry is created in
the list, but:

* Update the :c:member:`timestamp` field.
* Increment :c:member:`count`.
* Update the :c:member:`timestamp` field.
* Increment :c:member:`count`.

* To implement the counter facility, add a :c:func:`task_info_find_pid`
function that searches for a pid in the existing list.
* To implement the counter facility, add a :c:func:`task_info_find_pid`
function that searches for a pid in the existing list.

* If found, return the reference to the :c:type:`task_info` struct. If
not, return :c:macro:`NULL`.
* If found, return the reference to the :c:type:`task_info` struct. If
not, return :c:macro:`NULL`.

* An expiration facility. If a process was added more than 3
seconds ago and if it does not have a :c:member:`count` greater than 5 then
it is considered expired and is removed from the list.
* The expiration facility is already implemented in the
:c:func:`task_info_remove_expired` function.
* An expiration facility. If a process was added more than 3
seconds ago and if it does not have a :c:member:`count` greater than 5 then
it is considered expired and is removed from the list.
* The expiration facility is already implemented in the
:c:func:`task_info_remove_expired` function.

1. (TODO 1) Implement the :c:func:`task_info_find_pid` function.
2. (TODO 2) Change a field of an item in the list so it does not
expire. It must not satisfy a part of the expiration condition
from :c:func:`task_info_remove_expired`.
1. (TODO 1) Implement the :c:func:`task_info_find_pid` function.
2. (TODO 2) Change a field of an item in the list so it does not
expire. It must not satisfy a part of the expiration condition
from :c:func:`task_info_remove_expired`.

.. hint:: For ``TODO 2``, extract the first element from the list (the one
referred by :c:member:`head.next`) and set the :c:member:`count`
field to a large enough value. Use :c:func:`atomic_set` function.
.. hint:: For ``TODO 2``, extract the first element from the list (the one
referred by :c:member:`head.next`) and set the :c:member:`count`
field to a large enough value. Use :c:func:`atomic_set` function.

3. Compile, copy, load and unload the kernel module following the displayed
messages.
Kernel module loading will take some time, because :c:func:`sleep` is
being called by :c:func:`schedule_timeout` function.
3. Compile, copy, load and unload the kernel module following the displayed
messages.
Kernel module loading will take some time, because :c:func:`sleep` is
being called by :c:func:`schedule_timeout` function.

6. Synchronizing list work
--------------------------

Generate the skeleton for the task named **6-list-sync**.

1. Browse the code and look for ``TODO`` string.
2. Use a spinlock or a read-write lock to synchronize access to the
list.
3. Compile, load and unload the kernel module.
1. Browse the code and look for ``TODO`` string.
2. Use a spinlock or a read-write lock to synchronize access to the
list.
3. Compile, load and unload the kernel module.

.. important:: Always lock data, not code!

Expand Down
10 changes: 8 additions & 2 deletions tools/labs/Makefile
View file
Original file line number Diff line number Diff line change
Expand Up @@ -42,6 +42,12 @@ docs:
cp -r $(KDIR)/Documentation/output/slides/teaching/_static $(KDIR)/Documentation/output/teaching/

clean::
-rm -rf skels
$(MAKE) -C $(KDIR) M=$(KDIR)/tools/labs/skels ARCH=$(ARCH) clean
for i in $(shell find skels -name Makefile | xargs --no-run-if-empty dirname); do $(MAKE) -C $$i clean; done


clean_skels:
rm -rf skels

.PHONY: skels build copy docs clean clean_skels docker-docs

.PHONY: skels build copy docs clean docker-docs

0 comments on commit e5c318a

Please sign in to comment.