Add Task 16 description

Task16/task16.txt

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+This is Task 16 of the Eudyptula Challenge
+------------------------------------------
+
+Good job with the new syscall.  The odds of you ever having to write a
+new syscall is pretty rare, but now you know where to look them up, and
+what the code involved in creating one looks like, which is useful when
+you try to debug things.
+
+Let's take a breather after all of that code, and go back to doing a bit
+of reading, and learn some more about some common kernel tools.
+
+Go install the tool 'sparse'.  It was started by Linus as a
+static-analysis tool that acts much like a compiler.  The kernel build
+system is set up to have it run if you ask it to, and it will report a
+bunch of issues in C code that are really specific to the kernel.
+
+When you build the kernel, pass the "C=1" option to the build, to have
+sparse run on the .c file before gcc is run.  Depending on the file,
+nothing might be printed out, or something might.  Here's an example of
+it being run on the ext4 code:
+
+$ make C=1 M=fs/ext4
+  CHECK   fs/ext4/balloc.c
+  CC      fs/ext4/balloc.o
+  CHECK   fs/ext4/bitmap.c
+  CC      fs/ext4/bitmap.o
+  CHECK   fs/ext4/dir.c
+  CC      fs/ext4/dir.o
+  CHECK   fs/ext4/file.c
+  CC      fs/ext4/file.o
+  CHECK   fs/ext4/fsync.c
+  CC      fs/ext4/fsync.o
+  CHECK   fs/ext4/ialloc.c
+  CC      fs/ext4/ialloc.o
+  CHECK   fs/ext4/inode.c
+  CC      fs/ext4/inode.o
+  CHECK   fs/ext4/page-io.c
+  CC      fs/ext4/page-io.o
+  CHECK   fs/ext4/ioctl.c
+  CC      fs/ext4/ioctl.o
+  CHECK   fs/ext4/namei.c
+  CC      fs/ext4/namei.o
+  CHECK   fs/ext4/super.c
+  CC      fs/ext4/super.o
+  CHECK   fs/ext4/symlink.c
+  CC      fs/ext4/symlink.o
+  CHECK   fs/ext4/hash.c
+  CC      fs/ext4/hash.o
+  CHECK   fs/ext4/resize.c
+  CC      fs/ext4/resize.o
+  CHECK   fs/ext4/extents.c
+  CC      fs/ext4/extents.o
+  CHECK   fs/ext4/ext4_jbd2.c
+  CC      fs/ext4/ext4_jbd2.o
+  CHECK   fs/ext4/migrate.c
+  CC      fs/ext4/migrate.o
+  CHECK   fs/ext4/mballoc.c
+fs/ext4/mballoc.c:5018:9: warning: context imbalance in 'ext4_trim_extent' - unexpected unlock
+  CC      fs/ext4/mballoc.o
+  CHECK   fs/ext4/block_validity.c
+  CC      fs/ext4/block_validity.o
+  CHECK   fs/ext4/move_extent.c
+  CC      fs/ext4/move_extent.o
+  CHECK   fs/ext4/mmp.c
+  CC      fs/ext4/mmp.o
+  CHECK   fs/ext4/indirect.c
+  CC      fs/ext4/indirect.o
+  CHECK   fs/ext4/extents_status.c
+  CC      fs/ext4/extents_status.o
+  CHECK   fs/ext4/xattr.c
+  CC      fs/ext4/xattr.o
+  CHECK   fs/ext4/xattr_user.c
+  CC      fs/ext4/xattr_user.o
+  CHECK   fs/ext4/xattr_trusted.c
+  CC      fs/ext4/xattr_trusted.o
+  CHECK   fs/ext4/inline.c
+  CC      fs/ext4/inline.o
+  CHECK   fs/ext4/acl.c
+  CC      fs/ext4/acl.o
+  CHECK   fs/ext4/xattr_security.c
+  CC      fs/ext4/xattr_security.o
+  LD      fs/ext4/ext4.o
+  LD      fs/ext4/built-in.o
+  Building modules, stage 2.
+  MODPOST 0 modules
+
+As you can see, only one warning was found here, and odds are, it is a
+false-positive, as I'm sure those ext4 developers know what they are
+doing with their locking functions, right?
+
+Anyway the task this time is:
+  - Run sparse on the drivers/staging/ directory, yes, that horrible
+    code again, sorry.
+  - Find one warning that looks interesting.
+  - Write a patch that resolves the issue.
+  - Make sure the patch is correct by running it through
+    scripts/checkpatch.pl
+  - Submit the code to the maintainer of the driver/subsystem, finding
+    the proper name and mailing lists to send it to by running the tool,
+    scripts/get_maintainer.pl on your patch.
+  - Work with the maintainer to get the patch accepted into their tree.
+  - Send a web link back to me of your patch in the public mailing list
+    archive (don't cc: me on the patch, that will only confuse me and
+    everyone in the kernel development community) as well as a pointer
+    to the patch in the maintainer's public git tree.
+
+That's it, much like task 10 was, but this time you are fixing logical
+issues, not just pesky coding style issues.  You are a real developer
+now, fixing real bugs!