@func{main}, which never returns.
There's one more trick: the Pintos kernel command line
-is in stored the boot loader. The @command{pintos} program actually
+is stored in the boot loader. The @command{pintos} program actually
modifies a copy of the boot loader on disk each time it runs the kernel,
putting
in whatever command line arguments the user supplies to the kernel,
the loader stored it and put it into the @code{ram_pages} variable for
later use.
-Next, @func{thread_init} initializes the thread system. We will defer
-full discussion to our discussion of Pintos threads below. It is
-called so early in initialization because the console, initialized
-just afterward, tries to use locks, and locks in turn require there to be a
-running thread.
-
-Then we initialize the console so that @func{printf} will work.
-@func{main} calls @func{vga_init}, which initializes the VGA text
-display and clears the screen. It also calls @func{serial_init_poll}
-to initialize the first serial port in ``polling mode,'' that is,
-where the kernel busy-waits for the port to be ready for each
-character to be output. (We use polling mode until we're ready to enable
-interrupts, later.) Finally we initialize the console device and
-print a startup message to the console.
-
-@func{main} calls @func{read_command_line} to break the kernel command
+Next, @func{main} calls @func{read_command_line} to break the kernel command
line into arguments, then @func{parse_options} to read any options at
the beginning of the command line. (Actions specified on the
command line execute later.)
-@func{main} calls @func{random_init} to initialize the kernel random
-number generator. If the user specified @option{-rs} on the
-@command{pintos} command line, @func{parse_options} already did
-this, but calling it a second time is harmless.
+@func{thread_init} initializes the thread system. We will defer full
+discussion to our discussion of Pintos threads below. It is called so
+early in initialization because a valid thread structure is a
+prerequisite for acquiring a lock, and lock acquisition in turn is
+important to other Pintos subsystems. Then we initialize the console
+and print a startup message to the console.
-The next block of functions we call initialize the kernel's memory
+The next block of functions we call initializes the kernel's memory
system. @func{palloc_init} sets up the kernel page allocator, which
doles out memory one or more pages at a time (@pxref{Page Allocator}).
@func{malloc_init} sets
A @dfn{lock} is like a semaphore with an initial value of 1
(@pxref{Semaphores}). A lock's equivalent of ``up'' is called
-``acquire'', and the ``down'' operation is called ``release''.
+``release'', and the ``down'' operation is called ``acquire''.
Compared to a semaphore, a lock has one added restriction: only the
thread that acquires a lock, called the lock's ``owner'', is allowed to